# PaCkAgE DaTaStReAm
bash 1 15792
# end of header
0707010007eb28000081a40000000000000000000000015428b7c60000010900000100000100b5ffffffffffffffff0000000d00000000bash/pkginfo RSTATES=S s 1 2 3
ISTATES=S s 1 2 3
BASEDIR=/
CLASSES=none
CATEGORY=utility
ARCH=sparc
DESC=GNU bourne again shell
EMAIL=http://www.gnu.org/software/bash/
VENDOR=GNU
PSTAMP=29th September 2014
VERSION=4.3.p027
NAME=GNU bash 4.3.p027 SPARC 64bit Solaris 10
PKG=bash
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07070100000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000b00000000TRAILER!!! 0707010007eb28000081a40000000000000000000000015428b7c60000010900000100000100b5ffffffffffffffff0000000800000000pkginfo RSTATES=S s 1 2 3
ISTATES=S s 1 2 3
BASEDIR=/
CLASSES=none
CATEGORY=utility
ARCH=sparc
DESC=GNU bourne again shell
EMAIL=http://www.gnu.org/software/bash/
VENDOR=GNU
PSTAMP=29th September 2014
VERSION=4.3.p027
NAME=GNU bash 4.3.p027 SPARC 64bit Solaris 10
PKG=bash
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1 i pkginfo 265 20068 1411954630
0707010007ebb0000041ed0000000000000000000000025428b7c80000000000000100000100b5ffffffffffffffff0000000800000000install 0707010007ebb1000081ed0000000000000000000000015428b7c40000031100000100000100b5ffffffffffffffff0000001500000000install/checkinstall #!/bin/sh
#
expected_bits="64"
expected_release="5.10"
expected_platform="sparc"
#
release=`uname -r`
platform=`uname -p`
bits=`isainfo -b`
#
if [ ${platform} != ${expected_platform} ]; then
echo "\n\n\n\tThis package must be installed on a ${expected_platform} architecture\n"
echo "\tAborting installation.\n\n\n"
exit 1
fi
if [ ${release} != ${expected_release} ]; then
echo "\n\n\n\tThis package must be installed on a ${expected_release} machine\n"
echo "\tAborting installation.\n\n\n"
exit 1
fi
if [ ${bits} != ${expected_bits} ]; then
echo "\n\n\n\tThis package must be installed on a ${expected_bits} bit machine\n"
echo "\tYour machine is running a ${bits} bit O.S. currently\n"
echo "\tAborting installation.\n\n\n"
exit 1
fi
exit 0
0707010007eb29000041ed0000000000000000000000035428b7c70000000000000100000100b5ffffffffffffffff0000000500000000root 0707010007eb2a000041ed0000000000000000000000035428b7c70000000000000100000100b5ffffffffffffffff0000000900000000root/usr 0707010007eb2b000041ed0000000000000000000000045428b7c70000000000000100000100b5ffffffffffffffff0000000f00000000root/usr/local 0707010007eb2f000041ed0000000000000000000000065428b7c80000000000000100000100b5ffffffffffffffff0000001500000000root/usr/local/share 0707010007eb30000041ed0000000000000000000000035428b7c70000000000000100000100b5ffffffffffffffff0000001900000000root/usr/local/share/doc 0707010007eb31000041ed0000000000000000000000025428b7c80000000000000100000100b5ffffffffffffffff0000001e00000000root/usr/local/share/doc/bash 0707010007eb36000081a40000000000000000000000015428b73500012e1700000100000100b5ffffffffffffffff0000002300000000root/usr/local/share/doc/bash/NEWS This is a terse description of the new features added to bash-4.3 since
the release of bash-4.2. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. The `helptopic' completion action now maps to all the help topics, not just
the shell builtins.
b. The `help' builtin no longer does prefix substring matching first, so
`help read' does not match `readonly', but will do it if exact string
matching fails.
c. The shell can be compiled to not display a message about processes that
terminate due to SIGTERM.
d. Non-interactive shells now react to the setting of checkwinsize and set
LINES and COLUMNS after a foreground job exits.
e. There is a new shell option, `globasciiranges', which, when set to on,
forces globbing range comparisons to use character ordering as if they
were run in the C locale.
f. There is a new shell option, `direxpand', which makes filename completion
expand variables in directory names in the way bash-4.1 did.
g. In Posix mode, the `command' builtin does not change whether or not a
builtin it shadows is treated as an assignment builtin.
h. The `return' and `exit' builtins accept negative exit status arguments.
i. The word completion code checks whether or not a filename containing a
shell variable expands to a directory name and appends `/' to the word
as appropriate. The same code expands shell variables in command names
when performing command completion.
j. In Posix mode, it is now an error to attempt to define a shell function
with the same name as a Posix special builtin.
k. When compiled for strict Posix conformance, history expansion is disabled
by default.
l. The history expansion character (!) does not cause history expansion when
followed by the closing quote in a double-quoted string.
m. `complete' and its siblings compgen/compopt now takes a new `-o noquote'
option to inhibit quoting of the completions.
n. Setting HISTSIZE to a value less than zero causes the history list to be
unlimited (setting it 0 zero disables the history list).
o. Setting HISTFILESIZE to a value less than zero causes the history file size
to be unlimited (setting it to 0 causes the history file to be truncated
to zero size).
p. The `read' builtin now skips NUL bytes in the input.
q. There is a new `bind -X' option to print all key sequences bound to Unix
commands.
r. When in Posix mode, `read' is interruptible by a trapped signal. After
running the trap handler, read returns 128+signal and throws away any
partially-read input.
s. The command completion code skips whitespace and assignment statements
before looking for the command name word to be completed.
t. The build process has a new mechanism for constructing separate help files
that better reflects the current set of compilation options.
u. The -nt and -ot options to test now work with files with nanosecond
timestamp resolution.
v. The shell saves the command history in any shell for which history is
enabled and HISTFILE is set, not just interactive shells.
w. The shell has `nameref' variables and new -n(/+n) options to declare and
unset to use them, and a `test -R' option to test for them.
x. The shell now allows assigning, referencing, and unsetting elements of
indexed arrays using negative subscripts (a[-1]=2, echo ${a[-1]}) which
count back from the last element of the array.
y. The {x} operators to the [[ conditional command now do string
comparison according to the current locale if the compatibility level
is greater than 40.
r. Programmable completion now uses the completion for `b' instead of `a'
when completion is attempted on a line like: a $(b c.
s. Force extglob on temporarily when parsing the pattern argument to
the == and != operators to the [[ command, for compatibility.
t. Changed the behavior of interrupting the wait builtin when a SIGCHLD is
received and a trap on SIGCHLD is set to be Posix-mode only.
u. The read builtin has a new `-N nchars' option, which reads exactly NCHARS
characters, ignoring delimiters like newline.
v. The mapfile/readarray builtin no longer stores the commands it invokes via
callbacks in the history list.
w. There is a new `compat40' shopt option.
2. New Features in Readline
a. New bindable function: menu-complete-backward.
b. In the vi insertion keymap, C-n is now bound to menu-complete by default,
and C-p to menu-complete-backward.
c. When in vi command mode, repeatedly hitting ESC now does nothing, even
when ESC introduces a bound key sequence. This is closer to how
historical vi behaves.
d. New bindable function: skip-csi-sequence. Can be used as a default to
consume key sequences generated by keys like Home and End without having
to bind all keys.
e. New application-settable function: rl_filename_rewrite_hook. Can be used
to rewite or modify filenames read from the file system before they are
compared to the word to be completed.
f. New bindable variable: skip-completed-text, active when completing in the
middle of a word. If enabled, it means that characters in the completion
that match characters in the remainder of the word are "skipped" rather
than inserted into the line.
g. The pre-readline-6.0 version of menu completion is available as
"old-menu-complete" for users who do not like the readline-6.0 version.
h. New bindable variable: echo-control-characters. If enabled, and the
tty ECHOCTL bit is set, controls the echoing of characters corresponding
to keyboard-generated signals.
i. New bindable variable: enable-meta-key. Controls whether or not readline
sends the smm/rmm sequences if the terminal indicates it has a meta key
that enables eight-bit characters.
-------------------------------------------------------------------------------
This is a terse description of the new features added to bash-4.0 since
the release of bash-3.2. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. When using substring expansion on the positional parameters, a starting
index of 0 now causes $0 to be prefixed to the list.
b. The `help' builtin now prints its columns with entries sorted vertically
rather than horizontally.
c. There is a new variable, $BASHPID, which always returns the process id of
the current shell.
d. There is a new `autocd' option that, when enabled, causes bash to attempt
to `cd' to a directory name that is supplied as the first word of a
simple command.
e. There is a new `checkjobs' option that causes the shell to check for and
report any running or stopped jobs at exit.
f. The programmable completion code exports a new COMP_TYPE variable, set to
a character describing the type of completion being attempted.
g. The programmable completion code exports a new COMP_KEY variable, set to
the character that caused the completion to be invoked (e.g., TAB).
h. If creation of a child process fails due to insufficient resources, bash
will try again several times before reporting failure.
i. The programmable completion code now uses the same set of characters as
readline when breaking the command line into a list of words.
j. The block multiplier for the ulimit -c and -f options is now 512 when in
Posix mode, as Posix specifies.
k. Changed the behavior of the read builtin to save any partial input received
in the specified variable when the read builtin times out. This also
results in variables specified as arguments to read to be set to the empty
string when there is no input available. When the read builtin times out,
it returns an exit status greater than 128.
l. The shell now has the notion of a `compatibility level', controlled by
new variables settable by `shopt'. Setting this variable currently
restores the bash-3.1 behavior when processing quoted strings on the rhs
of the `=~' operator to the `[[' command.
m. The `ulimit' builtin now has new -b (socket buffer size) and -T (number
of threads) options.
n. The -p option to `declare' now displays all variable values and attributes
(or function values and attributes if used with -f).
o. There is a new `compopt' builtin that allows completion functions to modify
completion options for existing completions or the completion currently
being executed.
p. The `read' builtin has a new -i option which inserts text into the reply
buffer when using readline.
q. A new `-E' option to the complete builtin allows control of the default
behavior for completion on an empty line.
r. There is now limited support for completing command name words containing
globbing characters.
s. Changed format of internal help documentation for all builtins to roughly
follow man page format.
t. The `help' builtin now has a new -d option, to display a short description,
and a -m option, to print help information in a man page-like format.
u. There is a new `mapfile' builtin to populate an array with lines from a
given file. The name `readarray' is a synonym.
v. If a command is not found, the shell attempts to execute a shell function
named `command_not_found_handle', supplying the command words as the
function arguments.
w. There is a new shell option: `globstar'. When enabled, the globbing code
treats `**' specially -- it matches all directories (and files within
them, when appropriate) recursively.
x. There is a new shell option: `dirspell'. When enabled, the filename
completion code performs spelling correction on directory names during
completion.
y. The `-t' option to the `read' builtin now supports fractional timeout
values.
z. Brace expansion now allows zero-padding of expanded numeric values and
will add the proper number of zeroes to make sure all values contain the
same number of digits.
aa. There is a new bash-specific bindable readline function: `dabbrev-expand'.
It uses menu completion on a set of words taken from the history list.
bb. The command assigned to a key sequence with `bind -x' now sets two new
variables in the environment of the executed command: READLINE_LINE_BUFFER
and READLINE_POINT. The command can change the current readline line
and cursor position by modifying READLINE_LINE_BUFFER and READLINE_POINT,
respectively.
cc. There is a new &>> redirection operator, which appends the standard output
and standard error to the named file.
dd. The parser now understands `|&' as a synonym for `2>&1 |', which redirects
the standard error for a command through a pipe.
ee. The new `;&' case statement action list terminator causes execution to
continue with the action associated with the next pattern in the
statement rather than terminating the command.
ff. The new `;;&' case statement action list terminator causes the shell to
test the next set of patterns after completing execution of the current
action, rather than terminating the command.
gg. The shell understands a new variable: PROMPT_DIRTRIM. When set to an
integer value greater than zero, prompt expansion of \w and \W will
retain only that number of trailing pathname components and replace
the intervening characters with `...'.
hh. There are new case-modifying word expansions: uppercase (^[^]) and
lowercase (,[,]). They can work on either the first character or
array element, or globally. They accept an optional shell pattern
that determines which characters to modify. There is an optionally-
configured feature to include capitalization operators.
ii. The shell provides associative array variables, with the appropriate
support to create, delete, assign values to, and expand them.
jj. The `declare' builtin now has new -l (convert value to lowercase upon
assignment) and -u (convert value to uppercase upon assignment) options.
There is an optionally-configurable -c option to capitalize a value at
assignment.
kk. There is a new `coproc' reserved word that specifies a coprocess: an
asynchronous command run with two pipes connected to the creating shell.
Coprocs can be named. The input and output file descriptors and the
PID of the coprocess are available to the calling shell in variables
with coproc-specific names.
ll. A value of 0 for the -t option to `read' now returns success if there is
input available to be read from the specified file descriptor.
mm. CDPATH and GLOBIGNORE are ignored when the shell is running in privileged
mode.
nn. New bindable readline functions shell-forward-word and shell-backward-word,
which move forward and backward words delimited by shell metacharacters
and honor shell quoting.
oo. New bindable readline functions shell-backward-kill-word and shell-kill-word
which kill words backward and forward, but use the same word boundaries
as shell-forward-word and shell-backward-word.
2. New Features in Readline
a. A new variable, rl_sort_completion_matches; allows applications to inhibit
match list sorting (but beware: some things don't work right if
applications do this).
b. A new variable, rl_completion_invoking_key; allows applications to discover
the key that invoked rl_complete or rl_menu_complete.
c. The functions rl_block_sigint and rl_release_sigint are now public and
available to calling applications who want to protect critical sections
(like redisplay).
d. The functions rl_save_state and rl_restore_state are now public and
available to calling applications; documented rest of readline's state
flag values.
e. A new user-settable variable, `history-size', allows setting the maximum
number of entries in the history list.
f. There is a new implementation of menu completion, with several improvements
over the old; the most notable improvement is a better `completions
browsing' mode.
g. The menu completion code now uses the rl_menu_completion_entry_function
variable, allowing applications to provide their own menu completion
generators.
h. There is support for replacing a prefix of a pathname with a `...' when
displaying possible completions. This is controllable by setting the
`completion-prefix-display-length' variable. Matches with a common prefix
longer than this value have the common prefix replaced with `...'.
i. There is a new `revert-all-at-newline' variable. If enabled, readline will
undo all outstanding changes to all history lines when `accept-line' is
executed.
j. If the kernel supports it, readline displays special characters
corresponding to a keyboard-generated signal when the signal is received.
-------------------------------------------------------------------------------
This is a terse description of the new features added to bash-3.2 since
the release of bash-3.1. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. Changed the parameter pattern replacement functions to not anchor the
pattern at the beginning of the string if doing global replacement - that
combination doesn't make any sense.
b. When running in `word expansion only' mode (--wordexp option), inhibit
process substitution.
c. Loadable builtins now work on MacOS X 10.[34].
d. Shells running in posix mode no longer set $HOME, as POSIX requires.
e. The code that checks for binary files being executed as shell scripts now
checks only for NUL rather than any non-printing character.
f. Quoting the string argument to the [[ command's =~ operator now forces
string matching, as with the other pattern-matching operators.
2. New Features in Readline
a. Calling applications can now set the keyboard timeout to 0, allowing
poll-like behavior.
b. The value of SYS_INPUTRC (configurable at compilation time) is now used as
the default last-ditch startup file.
c. The history file reading functions now allow windows-like \r\n line
terminators.
-------------------------------------------------------------------------------
This is a terse description of the new features added to bash-3.1 since
the release of bash-3.0. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. Bash now understands LC_TIME as a special variable so that time display
tracks the current locale.
b. BASH_ARGC, BASH_ARGV, BASH_SOURCE, and BASH_LINENO are no longer created
as `invisible' variables and may not be unset.
c. In POSIX mode, if `xpg_echo' option is enabled, the `echo' builtin doesn't
try to interpret any options at all, as POSIX requires.
d. The `bg' builtin now accepts multiple arguments, as POSIX seems to specify.
e. Fixed vi-mode word completion and glob expansion to perform tilde
expansion.
f. The `**' mathematic exponentiation operator is now right-associative.
g. The `ulimit' builtin has new options: -i (max number of pending signals),
-q (max size of POSIX message queues), and -x (max number of file locks).
h. A bare `%' once again expands to the current job when used as a job
specifier.
i. The `+=' assignment operator (append to the value of a string or array) is
now supported for assignment statements and arguments to builtin commands
that accept assignment statements.
j. BASH_COMMAND now preserves its value when a DEBUG trap is executed.
k. The `gnu_errfmt' option is enabled automatically if the shell is running
in an emacs terminal window.
l. New configuration option: --single-help-strings. Causes long help text
to be written as a single string; intended to ease translation.
m. The COMP_WORDBREAKS variable now causes the list of word break characters
to be emptied when the variable is unset.
n. An unquoted expansion of $* when $IFS is empty now causes the positional
parameters to be concatenated if the expansion doesn't undergo word
splitting.
o. Bash now inherits $_ from the environment if it appears there at startup.
p. New shell option: nocasematch. If non-zero, shell pattern matching ignores
case when used by `case' and `[[' commands.
q. The `printf' builtin takes a new option: -v var. That causes the output
to be placed into var instead of on stdout.
r. By default, the shell no longer reports processes dying from SIGPIPE.
s. Bash now sets the extern variable `environ' to the export environment it
creates, so C library functions that call getenv() (and can't use the
shell-provided replacement) get current values of environment variables.
t. A new configuration option, `--enable-strict-posix-default', which will
build bash to be POSIX conforming by default.
u. If compiled for strict POSIX conformance, LINES and COLUMNS may now
override the true terminal size.
2. New Features in Readline
a. The key sequence sent by the keypad `delete' key is now automatically
bound to delete-char.
b. A negative argument to menu-complete now cycles backward through the
completion list.
c. A new bindable readline variable: bind-tty-special-chars. If non-zero,
readline will bind the terminal special characters to their readline
equivalents when it's called (on by default).
d. New bindable command: vi-rubout. Saves deleted text for possible
reinsertion, as with any vi-mode `text modification' command; `X' is bound
to this in vi command mode.
e. A new external application-controllable variable that allows the LINES
and COLUMNS environment variables to set the window size regardless of
what the kernel returns: rl_prefer_env_winsize
-------------------------------------------------------------------------------
This is a terse description of the new features added to bash-3.0 since
the release of bash-2.05b. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. ANSI string expansion now implements the \x{hexdigits} escape.
b. There is a new loadable `strftime' builtin.
c. New variable, COMP_WORDBREAKS, which controls the readline completer's
idea of word break characters.
d. The `type' builtin no longer reports on aliases unless alias expansion
will actually be performed.
e. HISTCONTROL is now a colon-separated list of values, which permits
more extensibility and backwards compatibility.
f. HISTCONTROL may now include the `erasedups' option, which causes all lines
matching a line being added to be removed from the history list.
g. `configure' has a new `--enable-multibyte' argument that permits multibyte
character support to be disabled even on systems that support it.
h. New variables to support the bash debugger: BASH_ARGC, BASH_ARGV,
BASH_SOURCE, BASH_LINENO, BASH_SUBSHELL, BASH_EXECUTION_STRING,
BASH_COMMAND
i. FUNCNAME has been changed to support the debugger: it's now an array
variable.
j. for, case, select, arithmetic commands now keep line number information
for the debugger.
k. There is a new `RETURN' trap executed when a function or sourced script
returns (not inherited child processes; inherited by command substitution
if function tracing is enabled and the debugger is active).
l. New invocation option: --debugger. Enables debugging and turns on new
`extdebug' shell option.
m. New `functrace' and `errtrace' options to `set -o' cause DEBUG and ERR
traps, respectively, to be inherited by shell functions. Equivalent to
`set -T' and `set -E' respectively. The `functrace' option also controls
whether or not the DEBUG trap is inherited by sourced scripts.
n. The DEBUG trap is run before binding the variable and running the action
list in a `for' command, binding the selection variable and running the
query in a `select' command, and before attempting a match in a `case'
command.
o. New `--enable-debugger' option to `configure' to compile in the debugger
support code.
p. `declare -F' now prints out extra line number and source file information
if the `extdebug' option is set.
q. If `extdebug' is enabled, a non-zero return value from a DEBUG trap causes
the next command to be skipped, and a return value of 2 while in a
function or sourced script forces a `return'.
r. New `caller' builtin to provide a call stack for the bash debugger.
s. The DEBUG trap is run just before the first command in a function body is
executed, for the debugger.
t. `for', `select', and `case' command heads are printed when `set -x' is
enabled.
u. There is a new {x..y} brace expansion, which is shorthand for {x.x+1,
x+2,...,y}. x and y can be integers or single characters; the sequence
may ascend or descend; the increment is always 1.
v. New ksh93-like ${!array[@]} expansion, expands to all the keys (indices)
of array.
w. New `force_fignore' shopt option; if enabled, suffixes specified by
FIGNORE cause words to be ignored when performing word completion even
if they're the only possibilities.
x. New `gnu_errfmt' shopt option; if enabled, error messages follow the `gnu
style' (filename:lineno:message) format.
y. New `-o bashdefault' option to complete and compgen; if set, causes the
whole set of bash completions to be performed if the compspec doesn't
result in a match.
z. New `-o plusdirs' option to complete and compgen; if set, causes directory
name completion to be performed and the results added to the rest of the
possible completions.
aa. `kill' is available as a builtin even when the shell is built without
job control.
bb. New HISTTIMEFORMAT variable; value is a format string to pass to
strftime(3). If set and not null, the `history' builtin prints out
timestamp information according to the specified format when displaying
history entries. If set, bash tells the history library to write out
timestamp information when the history file is written.
cc. The [[ ... ]] command has a new binary `=~' operator that performs
extended regular expression (egrep-like) matching.
dd. `configure' has a new `--enable-cond-regexp' option (enabled by default)
to enable the =~ operator and regexp matching in [[ ... ]].
ee. Subexpressions matched by the =~ operator are placed in the new
BASH_REMATCH array variable.
ff. New `failglob' option that causes an expansion error when pathname
expansion fails to produce a match.
gg. New `set -o pipefail' option that causes a pipeline to return a failure
status if any of the processes in the pipeline fail, not just the last
one.
hh. printf builtin understands two new escape sequences: \" and \?.
ii. `echo -e' understands two new escape sequences: \" and \?.
jj. The GNU `gettext' package and libintl have been integrated; the shell's
messages can be translated into different languages.
kk. The `\W' prompt expansion now abbreviates $HOME as `~', like `\w'.
ll. The error message printed when bash cannot open a shell script supplied
as argument 1 now includes the name of the shell, to better identify
the error as coming from bash.
mm. The parameter pattern removal and substitution expansions are now much
faster and more efficient when using multibyte characters.
nn. The `jobs', `kill', and `wait' builtins now accept job control notation
even if job control is not enabled.
oo. The historical behavior of `trap' that allows a missing `action' argument
to cause each specified signal's handling to be reset to its default is
now only supported when `trap' is given a single non-option argument.
2. New Features in Readline
a. History expansion has a new `a' modifier equivalent to the `g' modifier
for compatibility with the BSD csh.
b. History expansion has a new `G' modifier equivalent to the BSD csh `g'
modifier, which performs a substitution once per word.
c. All non-incremental search operations may now undo the operation of
replacing the current line with the history line.
d. The text inserted by an `a' command in vi mode can be reinserted with
`.'.
e. New bindable variable, `show-all-if-unmodified'. If set, the readline
completer will list possible completions immediately if there is more
than one completion and partial completion cannot be performed.
f. There is a new application-callable `free_history_entry()' function.
g. History list entries now contain timestamp information; the history file
functions know how to read and write timestamp information associated
with each entry.
h. Four new key binding functions have been added:
rl_bind_key_if_unbound()
rl_bind_key_if_unbound_in_map()
rl_bind_keyseq_if_unbound()
rl_bind_keyseq_if_unbound_in_map()
i. New application variable, rl_completion_quote_character, set to any
quote character readline finds before it calls the application completion
function.
j. New application variable, rl_completion_suppress_quote, settable by an
application completion function. If set to non-zero, readline does not
attempt to append a closing quote to a completed word.
k. New application variable, rl_completion_found_quote, set to a non-zero
value if readline determines that the word to be completed is quoted.
Set before readline calls any application completion function.
l. New function hook, rl_completion_word_break_hook, called when readline
needs to break a line into words when completion is attempted. Allows
the word break characters to vary based on position in the line.
m. New bindable command: unix-filename-rubout. Does the same thing as
unix-word-rubout, but adds `/' to the set of word delimiters.
n. When listing completions, directories have a `/' appended if the
`mark-directories' option has been enabled.
-------------------------------------------------------------------------------
This is a terse description of the new features added to bash-2.05b since
the release of bash-2.05a. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. If set, TMOUT is the default timeout for the `read' builtin.
b. `type' has two new options: `-f' suppresses shell function lookup, and
`-P' forces a $PATH search.
c. New code to handle multibyte characters.
d. `select' was changed to be more ksh-compatible, in that the menu is
reprinted each time through the loop only if REPLY is set to NULL.
The previous behavior is available as a compile-time option.
e. `complete -d' and `complete -o dirnames' now force a slash to be
appended to names which are symlinks to directories.
f. There is now a bindable edit-and-execute-command readline command,
like the vi-mode `v' command, bound to C-xC-e in emacs mode.
g. Added support for ksh93-like [:word:] character class in pattern matching.
h. The $'...' quoting construct now expands \cX to Control-X.
i. A new \D{...} prompt expansion; passes the `...' to strftime and inserts
the result into the expanded prompt.
j. The shell now performs arithmetic in the largest integer size the
machine supports (intmax_t), instead of long.
k. If a numeric argument is supplied to one of the bash globbing completion
functions, a `*' is appended to the word before expansion is attempted.
l. The bash globbing completion functions now allow completions to be listed
with double tabs or if `show-all-if-ambiguous' is set.
m. New `-o nospace' option for `complete' and `compgen' builtins; suppresses
readline's appending a space to the completed word.
n. New `here-string' redirection operator: <<< word.
o. When displaying variables, function attributes and definitions are shown
separately, allowing them to be re-used as input (attempting to re-use
the old output would result in syntax errors).
p. There is a new configuration option `--enable-mem-scramble', controls
bash malloc behavior of writing garbage characters into memory at
allocation and free time.
q. The `complete' and `compgen' builtins now have a new `-s/-A service'
option to complete on names from /etc/services.
r. `read' has a new `-u fd' option to read from a specified file descriptor.
s. Fix the completion code so that expansion errors in a directory name
don't cause a longjmp back to the command loop.
t. Fixed word completion inside command substitution to work a little more
intuitively.
u. The `printf' %q format specifier now uses $'...' quoting to print the
argument if it contains non-printing characters.
v. The `declare' and `typeset' builtins have a new `-t' option. When applied
to functions, it causes the DEBUG trap to be inherited by the named
function. Currently has no effect on variables.
w. The DEBUG trap is now run *before* simple commands, ((...)) commands,
[[...]] conditional commands, and for ((...)) loops.
x. The expansion of $LINENO inside a shell function is only relative to the
function start if the shell is interactive -- if the shell is running a
script, $LINENO expands to the line number in the script. This is as
POSIX-2001 requires.
y. The bash debugger in examples/bashdb has been modified to work with the
new DEBUG trap semantics, the command set has been made more gdb-like,
and the changes to $LINENO make debugging functions work better. Code
from Gary Vaughan.
z. New [n]<&word- and [n]>&word- redirections from ksh93 -- move fds (dup
and close).
aa. There is a new `-l' invocation option, equivalent to `--login'.
bb. The `hash' builtin has a new `-l' option to list contents in a reusable
format, and a `-d' option to remove a name from the hash table.
cc. There is now support for placing the long help text into separate files
installed into ${datadir}/bash. Not enabled by default; can be turned
on with `--enable-separate-helpfiles' option to configure.
dd. All builtins that take operands accept a `--' pseudo-option, except
`echo'.
ee. The `echo' builtin now accepts \0xxx (zero to three octal digits following
the `0') in addition to \xxx (one to three octal digits) for SUSv3/XPG6/
POSIX.1-2001 compliance.
2. New Features in Readline
a. Support for key `subsequences': allows, e.g., ESC and ESC-a to both
be bound to readline functions. Now the arrow keys may be used in vi
insert mode.
b. When listing completions, and the number of lines displayed is more than
the screen length, readline uses an internal pager to display the results.
This is controlled by the `page-completions' variable (default on).
c. New code to handle editing and displaying multibyte characters.
d. The behavior introduced in bash-2.05a of deciding whether or not to
append a slash to a completed name that is a symlink to a directory has
been made optional, controlled by the `mark-symlinked-directories'
variable (default is the 2.05a behavior).
e. The `insert-comment' command now acts as a toggle if given a numeric
argument: if the first characters on the line don't specify a
comment, insert one; if they do, delete the comment text
f. New application-settable completion variable:
rl_completion_mark_symlink_dirs, allows an application's completion
function to temporarily override the user's preference for appending
slashes to names which are symlinks to directories.
g. New function available to application completion functions:
rl_completion_mode, to tell how the completion function was invoked
and decide which argument to supply to rl_complete_internal (to list
completions, etc.).
h. Readline now has an overwrite mode, toggled by the `overwrite-mode'
bindable command, which could be bound to `Insert'.
i. New application-settable completion variable:
rl_completion_suppress_append, inhibits appending of
rl_completion_append_character to completed words.
j. New key bindings when reading an incremental search string: ^W yanks
the currently-matched word out of the current line into the search
string; ^Y yanks the rest of the current line into the search string,
DEL or ^H deletes characters from the search string.
-------------------------------------------------------------------------------
This is a terse description of the new features added to bash-2.05a since
the release of bash-2.05. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. Added support for DESTDIR installation root prefix, so you can do a
`make install DESTDIR=bash-root' and do easier binary packaging.
b. Added support for builtin printf "'" flag character as per latest POSIX
drafts.
c. Support for POSIX.2 printf(1) length specifiers `j', `t', and `z' (from
ISO C99).
d. New autoconf macro, RL_LIB_READLINE_VERSION, for use by other applications
(bash doesn't use very much of what it returns).
e. `set [-+]o nolog' is recognized as required by the latest POSIX drafts,
but ignored.
f. New read-only `shopt' option: login_shell. Set to non-zero value if the
shell is a login shell.
g. New `\A' prompt string escape sequence; expands to time in 24 HH:MM format.
h. New `-A group/-g' option to complete and compgen; does group name
completion.
i. New `-t' option to `hash' to list hash values for each filename argument.
j. New [-+]O invocation option to set and unset `shopt' options at startup.
k. configure's `--with-installed-readline' option now takes an optional
`=PATH' suffix to set the root of the tree where readline is installed
to PATH.
l. The ksh-like `ERR' trap has been added. The `ERR' trap will be run
whenever the shell would have exited if the -e option were enabled.
It is not inherited by shell functions.
m. `readonly', `export', and `declare' now print variables which have been
given attributes but not set by assigning a value as just a command and
a variable name (like `export foo') when listing, as the latest POSIX
drafts require.
n. `bashbug' now requires that the subject be changed from the default.
o. configure has a new `--enable-largefile' option, like other GNU utilities.
p. `for' loops now allow empty word lists after `in', like the latest POSIX
drafts require.
q. The builtin `ulimit' now takes two new non-numeric arguments: `hard',
meaning the current hard limit, and `soft', meaning the current soft
limit, in addition to `unlimited'
r. `ulimit' now prints the option letter associated with a particular
resource when printing more than one limit.
s. `ulimit' prints `hard' or `soft' when a value is not `unlimited' but is
one of RLIM_SAVED_MAX or RLIM_SAVED_CUR, respectively.
t. The `printf' builtin now handles the %a and %A conversions if they're
implemented by printf(3).
u. The `printf' builtin now handles the %F conversion (just about like %f).
v. The `printf' builtin now handles the %n conversion like printf(3). The
corresponding argument is the name of a shell variable to which the
value is assigned.
2. New Features in Readline
a. Added extern declaration for rl_get_termcap to readline.h, making it a
public function (it was always there, just not in readline.h).
b. New #defines in readline.h: RL_READLINE_VERSION, currently 0x0402,
RL_VERSION_MAJOR, currently 4, and RL_VERSION_MINOR, currently 2.
c. New readline variable: rl_readline_version, mirrors RL_READLINE_VERSION.
d. New bindable boolean readline variable: match-hidden-files. Controls
completion of files beginning with a `.' (on Unix). Enabled by default.
e. The history expansion code now allows any character to terminate a
`:first-' modifier, like csh.
f. New bindable variable `history-preserve-point'. If set, the history
code attempts to place the user at the same location on each history
line retrived with previous-history or next-history.
-------------------------------------------------------------------------------
This is a terse description of the new features added to bash-2.05 since
the release of bash-2.04. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. Added a new `--init-file' invocation argument as a synonym for `--rcfile',
per the new GNU coding standards.
b. The /dev/tcp and /dev/udp redirections now accept service names as well as
port numbers.
c. `complete' and `compgen' now take a `-o value' option, which controls some
of the aspects of that compspec. Valid values are:
default - perform bash default completion if programmable
completion produces no matches
dirnames - perform directory name completion if programmable
completion produces no matches
filenames - tell readline that the compspec produces filenames,
so it can do things like append slashes to
directory names and suppress trailing spaces
d. A new loadable builtin, realpath, which canonicalizes and expands symlinks
in pathname arguments.
e. When `set' is called without options, it prints function defintions in a
way that allows them to be reused as input. This affects `declare' and
`declare -p' as well. This only happens when the shell is not in POSIX
mode, since POSIX.2 forbids this behavior.
f. Bash-2.05 once again honors the current locale setting when processing
ranges within pattern matching bracket expressions (e.g., [A-Z]).
2. New Features in Readline
a. The blink timeout for paren matching is now settable by applications,
via the rl_set_paren_blink_timeout() function.
b. _rl_executing_macro has been renamed to rl_executing_macro, which means
it's now part of the public interface.
c. Readline has a new variable, rl_readline_state, which is a bitmap that
encapsulates the current state of the library; intended for use by
callbacks and hook functions.
d. New application-callable function rl_set_prompt(const char *prompt):
expands its prompt string argument and sets rl_prompt to the result.
e. New application-callable function rl_set_screen_size(int rows, int cols):
public method for applications to set readline's idea of the screen
dimensions.
f. New function, rl_get_screen_size (int *rows, int *columns), returns
readline's idea of the screen dimensions.
g. The timeout in rl_gather_tyi (readline keyboard input polling function)
is now settable via a function (rl_set_keyboard_input_timeout()).
h. Renamed the max_input_history variable to history_max_entries; the old
variable is maintained for backwards compatibility.
i. The list of characters that separate words for the history tokenizer is
now settable with a variable: history_word_delimiters. The default
value is as before.
-------------------------------------------------------------------------------
This is a terse description of the new features added to bash-2.04 since
the release of bash-2.03. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. The history builtin has a `-d offset' option to delete the history entry
at position `offset'.
b. The prompt expansion code has two new escape sequences: \j, the number of
active jobs; and \l, the basename of the shell's tty device name.
c. The `bind' builtin has a new `-x' option to bind key sequences to shell
commands.
d. There is a new shell option, no_empty_command_completion, which, when
enabled, disables command completion when TAB is typed on an empty line.
e. The `help' builtin has a `-s' option to just print a builtin's usage
synopsis.
f. There are several new arithmetic operators: id++, id-- (variable
post-increment/decrement), ++id, --id (variable pre-increment/decrement),
expr1 , expr2 (comma operator).
g. There is a new ksh-93 style arithmetic for command:
for ((expr1 ; expr2; expr3 )); do list; done
h. The `read' builtin has a number of new options:
-t timeout only wait timeout seconds for input
-n nchars only read nchars from input instead of a full line
-d delim read until delim rather than newline
-s don't echo input chars as they are read
i. The redirection code now handles several filenames specially:
/dev/fd/N, /dev/stdin, /dev/stdout, and /dev/stderr, whether or
not they are present in the file system.
j. The redirection code now recognizes pathnames of the form
/dev/tcp/host/port and /dev/udp/host/port, and tries to open a socket
of the appropriate type to the specified port on the specified host.
k. The ksh-93 ${!prefix*} expansion, which expands to the names of all
shell variables with prefix PREFIX, has been implemented.
l. There is a new dynamic variable, FUNCNAME, which expands to the name of
a currently-executing function. Assignments to FUNCNAME have no effect.
m. The GROUPS variable is no longer readonly; assignments to it are silently
discarded. This means it can be unset.
n. A new programmable completion facility, with two new builtin commands:
complete and compgen.
o. configure has a new option, `--enable-progcomp', to compile in the
programmable completion features (enabled by default).
p. `shopt' has a new option, `progcomp', to enable and disable programmable
completion at runtime.
q. Unsetting HOSTFILE now clears the list of hostnames used for completion.
r. configure has a new option, `--enable-bash-malloc', replacing the old
`--with-gnu-malloc' (which is still present for backwards compatibility).
s. There is a new manual page describing rbash, the restricted shell.
t. `bashbug' has new `--help' and `--version' options.
u. `shopt' has a new `xpg_echo' option, which controls the behavior of
`echo' with respect to backslash-escaped characters at runtime.
v. If NON_INTERACTIVE_LOGIN_SHELLS is defined, all login shells read the
startup files, even if they are not interactive.
w. The LC_NUMERIC variable is now treated specially, and used to set the
LC_NUMERIC locale category for number formatting, e.g., when `printf'
displays floating-point numbers.
2. New features in Readline
a. Parentheses matching is now always compiled into readline, and enabled
or disabled when the value of the `blink-matching-paren' variable is
changed.
b. MS-DOS systems now use ~/_inputrc as the last-ditch inputrc filename.
c. MS-DOS systems now use ~/_history as the default history file.
d. history-search-{forward,backward} now leave the point at the end of the
line when the string to search for is empty, like
{reverse,forward}-search-history.
e. history-search-{forward,backward} now leave the last history line found
in the readline buffer if the second or subsequent search fails.
f. New function for use by applications: rl_on_new_line_with_prompt, used
when an application displays the prompt itself before calling readline().
g. New variable for use by applications: rl_already_prompted. An application
that displays the prompt itself before calling readline() must set this to
a non-zero value.
h. A new variable, rl_gnu_readline_p, always 1. The intent is that an
application can verify whether or not it is linked with the `real'
readline library or some substitute.
-------------------------------------------------------------------------------
This is a terse description of the new features added to bash-2.03 since
the release of bash-2.02. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. New `shopt' option, `restricted_shell', indicating whether or not the
shell was started in restricted mode, for use in startup files.
b. Filename generation is now performed on the words between ( and ) in
array assignments (which it probably should have done all along).
c. OLDPWD is now auto-exported, as POSIX.2 seems to require.
d. ENV and BASH_ENV are read-only variables in a restricted shell.
e. A change was made to the startup file code so that any shell begun with
the `--login' option, even non-interactive shells, will source the login
shell startup files.
2. New Features in Readline
a. Many changes to the signal handling:
o Readline now catches SIGQUIT and cleans up the tty before returning;
o A new variable, rl_catch_signals, is available to application writers
to indicate to readline whether or not it should install its own
signal handlers for SIGINT, SIGTERM, SIGQUIT, SIGALRM, SIGTSTP,
SIGTTIN, and SIGTTOU;
o A new variable, rl_catch_sigwinch, is available to application
writers to indicate to readline whether or not it should install its
own signal handler for SIGWINCH, which will chain to the calling
applications's SIGWINCH handler, if one is installed;
o There is a new function, rl_free_line_state, for application signal
handlers to call to free up the state associated with the current
line after receiving a signal;
o There is a new function, rl_cleanup_after_signal, to clean up the
display and terminal state after receiving a signal;
o There is a new function, rl_reset_after_signal, to reinitialize the
terminal and display state after an application signal handler
returns and readline continues
b. There is a new function, rl_resize_terminal, to reset readline's idea of
the screen size after a SIGWINCH.
c. New public functions: rl_save_prompt and rl_restore_prompt. These were
previously private functions with a `_' prefix.
d. New function hook: rl_pre_input_hook, called just before readline starts
reading input, after initialization.
e. New function hook: rl_display_matches_hook, called when readline would
display the list of completion matches. The new function
rl_display_match_list is what readline uses internally, and is available
for use by application functions called via this hook.
f. New bindable function, delete-char-or-list, like tcsh.
g. A new variable, rl_erase_empty_line, which, if set by an application using
readline, will cause readline to erase, prompt and all, lines on which the
only thing typed was a newline.
h. New bindable variable: `isearch-terminators'.
i. New bindable function: `forward-backward-delete-char' (unbound by default).
-------------------------------------------------------------------------------
This is a terse description of the new features added to bash-2.02 since
the release of bash-2.01.1. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. A new version of malloc, based on the older GNU malloc, that has many
changes, is more page-based, is more conservative with memory usage,
and does not `orphan' large blocks when they are freed.
b. A new version of gmalloc, based on the old GLIBC malloc, with many
changes and range checking included by default.
c. A new implementation of fnmatch(3) that includes full POSIX.2 Basic
Regular Expression matching, including character classes, collating
symbols, equivalence classes, and support for case-insensitive pattern
matching.
d. ksh-88 egrep-style extended pattern matching ([@+*?!](patlist)) has been
implemented, controlled by a new `shopt' option, `extglob'.
e. There is a new ksh-like `[[' compound command, which implements
extended `test' functionality.
f. There is a new `printf' builtin, implemented according to the POSIX.2
specification.
g. There is a new feature for command substitution: $(< filename) now expands
to the contents of `filename', with any trailing newlines removed
(equivalent to $(cat filename)).
h. There are new tilde prefixes which expand to directories from the
directory stack.
i. There is a new `**' arithmetic operator to do exponentiation.
j. There are new configuration options to control how bash is linked:
`--enable-profiling', to allow bash to be profiled with gprof, and
`--enable-static-link', to allow bash to be linked statically.
k. There is a new configuration option, `--enable-cond-command', which
controls whether or not the `[[' command is included. It is on by
default.
l. There is a new configuration option, `--enable-extended-glob', which
controls whether or not the ksh extended globbing feature is included.
It is enabled by default.
m. There is a new configuration #define in config.h.top that, when enabled,
will cause all login shells to source /etc/profile and one of the user-
specific login shell startup files, whether or not the shell is
interactive.
n. There is a new invocation option, `--dump-po-strings', to dump
a shell script's translatable strings ($"...") in GNU `po' format.
o. There is a new `shopt' option, `nocaseglob', to enable case-insensitive
pattern matching when globbing filenames and using the `case' construct.
p. There is a new `shopt' option, `huponexit', which, when enabled, causes
the shell to send SIGHUP to all jobs when an interactive login shell
exits.
q. `bind' has a new `-u' option, which takes a readline function name as an
argument and unbinds all key sequences bound to that function in a
specified keymap.
r. `disown' now has `-a' and `-r' options, to limit operation to all jobs
and running jobs, respectively.
s. The `shopt' `-p' option now causes output to be displayed in a reusable
format.
t. `test' has a new `-N' option, which returns true if the filename argument
has been modified since it was last accessed.
u. `umask' now has a `-p' option to print output in a reusable format.
v. A new escape sequence, `\xNNN', has been added to the `echo -e' and $'...'
translation code. It expands to the character whose ascii code is NNN
in hexadecimal.
w. The prompt string expansion code has a new `\r' escape sequence.
x. The shell may now be cross-compiled for the CYGWIN32 environment on
a Unix machine.
2. New Features in Readline
a. There is now an option for `iterative' yank-last-arg handline, so a user
can keep entering `M-.', yanking the last argument of successive history
lines.
b. New variable, `print-completions-horizontally', which causes completion
matches to be displayed across the screen (like `ls -x') rather than up
and down the screen (like `ls').
c. New variable, `completion-ignore-case', which causes filename completion
and matching to be performed case-insensitively.
d. There is a new bindable command, `magic-space', which causes history
expansion to be performed on the current readline buffer and a space to
be inserted into the result.
e. There is a new bindable command, `menu-complete', which enables tcsh-like
menu completion (successive executions of menu-complete insert a single
completion match, cycling through the list of possible completions).
f. There is a new bindable command, `paste-from-clipboard', for use on Win32
systems, to insert the text from the Win32 clipboard into the editing
buffer.
g. The key sequence translation code now understands printf-style backslash
escape sequences, including \NNN octal escapes. These escape sequences
may be used in key sequence definitions or macro values.
h. An `$include' inputrc file parser directive has been added.
-------------------------------------------------------------------------------
This is a terse description of the new features added to bash-2.01 since
the release of bash-2.0. As always, the manual page (doc/bash.1) is the
place to look for complete descriptions.
1. New Features in Bash
a. There is a new builtin array variable: GROUPS, the set of groups to which
the user belongs. This is used by the test suite.
2. New Features in Readline
a. If a key sequence bound to `universal-argument' is read while reading a
numeric argument started with `universal-argument', it terminates the
argument but is otherwise ignored. This provides a way to insert multiple
instances of a digit string, and is how GNU emacs does it.
-------------------------------------------------------------------------------
This is a terse description of the new features added to bash-2.0 since
the release of bash-1.14.7. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. There is a new invocation option, -D, that dumps translatable strings
in a script.
b. The `long' invocation options must now be prefixed with `--'.
c. New long invocation options: --dump-strings, --help, --verbose
d. The `nolineediting' invocation option was renamed to `noediting'.
e. The `nobraceexpansion' and `quiet' long invocation options were removed.
f. The `--help' and `--version' long options now work as the GNU coding
standards specify.
g. If invoked as `sh', bash now enters posix mode after reading the
startup files, and reads and executes commands from the file named
by $ENV if interactive (as POSIX.2 specifies). A login shell invoked
as `sh' reads $ENV after /etc/profile and ~/.profile.
h. There is a new reserved word, `time', for timing pipelines, builtin
commands, and shell functions. It uses the value of the TIMEFORMAT
variable as a format string describing how to print the timing
statistics.
i. The $'...' quoting syntax expands ANSI-C escapes in ... and leaves the
result single-quoted.
j. The $"..." quoting syntax performs locale-specific translation of ...
and leaves the result double-quoted.
k. LINENO now works correctly in functions.
l. New variables: DIRSTACK, PIPESTATUS, BASH_VERSINFO, HOSTNAME, SHELLOPTS,
MACHTYPE. The first three are array variables.
m. The BASH_VERSION and BASH_VERSINFO variables now include the shell's
`release status' (alpha[N], beta[N], release).
n. Some variables have been removed: MAIL_WARNING, notify, history_control,
command_oriented_history, glob_dot_filenames, allow_null_glob_expansion,
nolinks, hostname_completion_file, noclobber, no_exit_on_failed_exec, and
cdable_vars. Most of them are now implemented with the new `shopt'
builtin; others were already implemented by `set'.
o. Bash now uses some new variables: LC_ALL, LC_MESSAGES, LC_CTYPE,
LC_COLLATE, LANG, GLOBIGNORE, HISTIGNORE.
p. The shell now supports integer-indexed arrays of unlimited length,
with a new compound assignment syntax and changes to the appropriate
builtin commands (declare/typeset, read, readonly, etc.). The array
index may be an arithmetic expression.
q. ${!var}: indirect variable expansion, equivalent to eval \${$var}.
r. ${paramter:offset[:length]}: variable substring extraction.
s. ${parameter/pattern[/[/]string]}: variable pattern substitution.
t. The $[...] arithmetic expansion syntax is no longer supported, in
favor of $((...)).
u. Aliases can now be expanded in shell scripts with a shell option
(shopt expand_aliases).
v. History and history expansion can now be used in scripts with
set -o history and set -H.
w. All builtins now return an exit status of 2 for incorrect usage.
x. Interactive shells resend SIGHUP to all running or stopped children
if (and only if) they exit due to a SIGHUP.
y. New prompting expansions: \a, \e, \H, \T, \@, \v, \V.
z. Variable expansion in prompt strings is now controllable via a shell
option (shopt promptvars).
aa. Bash now defaults to using command-oriented history.
bb. The history file ($HISTFILE) is now truncated to $HISTFILESIZE after
being written.
cc. The POSIX.2 conditional arithmetic evaluation syntax (expr ? expr : expr)
has been implemented.
dd. Each builtin now accepts `--' to signify the end of the options, except
as documented (echo, etc.).
ee. All builtins use -p to display values in a re-readable format where
appropriate, except as documented (echo, type, etc.).
ff. The `alias' builtin has a new -p option.
gg. Changes to the `bind' builtin:
o has new options: -psPSVr.
o the `-d' option was renamed to `-p'
o the `-v' option now dumps variables; the old `-v' is now `-P'
hh. The `bye' synonym for `exit' was removed.
ii. The -L and -P options to `cd' and `pwd' have been documented.
jj. The `cd' builtin now does spelling correction on the directory name
by default. This is settable with a shell option (shopt cdspell).
kk. The `declare' builtin has new options: -a, -F, -p.
ll. The `dirs' builtin has new options: -c, -p, -v.
mm. The new `disown' builtin removes jobs from the shell's jobs table
or inhibits the resending of SIGHUP when the shell receives a
SIGHUP.
nn. The `echo' builtin has a new escape character: \e.
oo. The `enable' builtin can now load new builtins dynamically from shared
objects on systems with the dlopen/dlsym interface. There are a number
of examples in the examples/loadables directory. There are also
new options: -d, -f, -s, -p.
pp. The `-all' option to `enable' was removed in favor of `-a'.
qq. The `exec' builtin has new options: -l, -c, -a.
rr. The `hash' builtin has a new option: -p.
ss. The `history' builtin has new options: -c, -p, -s.
tt. The `jobs' builtin has new options: -r, -s.
uu. The `kill' builtin has new options: -n signum, -l signame.
vv. The `pushd' and `popd' builtins have a new option: -n.
ww. The `read' builtin has new options: -p prompt, -e, -a.
xx. The `readonly' builtin has a new -a option, and the -n option was removed.
yy. Changes to the `set' builtin:
o new options: -B, -o keyword, -o onecmd, -o history
o options removed: -l, -d, -o nohash
o options changed: +o, -h, -o hashall
o now displays variables in a format that can be re-read as input
zz. The new `shopt' builtin controls shell optional behavior previously
done by setting and unsetting certain shell variables.
aaa. The `test' builtin has new operators: -o option, s1 == s2, s1 < s2,
and s1 > s2, where s1 and s2 are strings.
bbb. There is a new trap, DEBUG, executed after every simple command.
ccc. The `trap' builtin has a new -p option.
ddd. The `ulimit' builtin has a new -l option on 4.4BSD-based systems.
eee. The PS1, PS2, PATH, and IFS variables may now be unset.
fff. The restricted shell mode has been expanded and is now documented.
ggg. Security improvements:
o functions are not imported from the environment if running setuid
or with -p
o no startup files are sourced if running setuid or with -p
hhh. The documentation has been overhauled: the texinfo manual was
expanded, and HTML versions of the man page and texinfo manual
are included.
iii. Changes to Posix mode:
o Command lookup now finds special builtins before shell functions.
o Failure of a special builtin causes a non-interactive shell to
exit. Failures are defined in the POSIX.2 specification.
o If the `cd' builtin finds a directory to change to using $CDPATH,
the value assigned to PWD when `cd' completes does not contain
any symbolic links.
o A non-interactive shell exits if a variable assignment error
occurs when no command name follows the assignment statements.
o A non-interactive shell exits if the interation variable in a
`for' statement or the selection variable in a `select' statement
is read-only or another variable assignment error occurs.
o The `<>' redirection operator now opens a file for both stdin and
stdout by default, not just when in posix mode.
o Assignment statements preceding special builtins now persist in
the shell's environment when the builtin completes.
Posix mode is now completely POSIX.2-compliant (modulo bugs). When
invoked as sh, bash should be completely POSIX.2-compliant.
jjj. The default value of PS1 is now "\s-\v\$ ".
kkk. The ksh-like ((...)) arithmetic command syntax has been implemented.
This is exactly equivalent to `let "..."'.
lll. Integer constants have been extended to base 64.
mmm. The `ulimit' builtin now sets both hard and soft limits and reports the
soft limit by default.
2. New Features in Readline
a. New variables: enable-keypad, input-meta (new name for meta-flag),
mark-directories, visible-stats (now documented), disable-completion,
comment-begin.
b. New bindable commands: kill-region, copy-region-as-kill,
copy-backward-word, copy-forward-word, set-mark, exchange-point-and-mark,
character-search, character-search-backward, insert-comment,
glob-expand-word, glob-list-expansions, dump-variables, dump-macros.
c. New emacs keybindings: delete-horizontal-space (M-\),
insert-completions (M-*), possible-completions (M-=).
d. The history-search-backward and history-search-forward commands were
modified to be the same as previous-line and next-line if point is at
the start of the line.
e. More file types are available for the visible-stats mode.
3. Changes of interest in the Bash implementation
a. There is a new autoconf-based configuration mechanism.
b. More things have been moved from Posix mode to standard shell behavior.
c. The trace output (set -x) now inserts quotes where necessary so it can
be reused as input.
d. There is a compile-time option for a system-wide interactive shell
startup file (disabled by default).
e. The YACC grammar is smaller and tighter, and all 66 shift-reduce
conflicts are gone. Several parsing bugs have been fixed.
f. Builtin option parsing has been regularized (using internal_getopt()),
with the exception of `echo', `type', and `set'.
g. Builtins now return standard usage messages constructed from the
`short doc' used by the help builtin.
h. Completion now quotes using backslashes by default, but honors
user-supplied quotes.
i. The GNU libc malloc is available as a configure-time option.
j. There are more internationalization features; bash uses gettext if
it is available. The $"..." translation syntax uses the current
locale and gettext.
k. There is better reporting of job termination when the shell is not
interactive.
l. The shell is somewhat more efficient: it uses a little less memory and
makes fewer system calls.
4. Changes of interest in the Readline implementation
a. There is now support for readline `callback' functions.
b. There is now support for user-supplied input, redisplay, and terminal
preparation functions.
c. Most of the shell-specific code in readline has been generalized or
removed.
d. Most of the annoying redisplay bugs have been fixed, notably the problems
with incremental search and excessive redrawing when special characters
appear in the prompt string.
e. There are new library functions and variables available to application
writers, most having to do with completion and quoting.
f. The NEWLINE character (^J) is now treated as a search terminator by the
incremental search functions.
-------------------------------------------------------------------------------
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved. This file is offered as-is,
without any warranty.
0707010007eb35000081a40000000000000000000000015428b73500001ba000000100000100b5ffffffffffffffff0000002400000000root/usr/local/share/doc/bash/INTRO BASH - The Bourne-Again Shell
Bash is the shell, or command language interpreter, that will appear
in the GNU operating system. Bash is an sh-compatible shell that
incorporates useful features from the Korn shell (ksh) and C shell
(csh). It is intended to conform to the IEEE POSIX P1003.2/ISO 9945.2
Shell and Tools standard. It offers functional improvements over sh
for both programming and interactive use. In addition, most sh scripts
can be run by Bash without modification.
Bash is quite portable. It uses a configuration system that discovers
characteristics of the compilation platform at build time, and may
therefore be built on nearly every version of UNIX. Ports to
UNIX-like systems such as QNX and Minix and to non-UNIX systems such
as OS/2, Windows 95, and Windows NT are available.
Bash includes the following features:
Editing and Completion
Bash offers a command-line editing facility which permits users to
edit command lines using familiar emacs or vi-style editing commands.
Editing allows corrections to be made without having to erase back
to the point of error or start the command line anew. The editing
facilities include a feature that allows users to complete command and
file names.
The Bash line editing library is fully customizable. Users may define
their own key bindings -- the action taken when a key is pressed. A
number of variables to fine-tune editing behavior are also available.
History and Command Re-entry
The Bash history feature remembers commands entered to the shell and
allows them to be recalled and re-executed. The history list may be
of unlimited size. Bash allows users to search for previous commands
and reuse portions of those commands when composing new ones. The
history list may be saved across shell sessions.
Bash allows users to control which commands are saved on the history
list.
Job Control
On systems that support it, Bash provides an interface to the
operating system's job control facilities, which allow processes
to be suspended and restarted, and moved between the foreground
and background. Bash allows users to selectively `forget' about
background jobs.
Shell Functions and Aliases
These mechanisms are available to bind a user-selected identifier to a
list of commands that will be executed when the identifier is used as
a command name. Functions allow local variables and recursion, and
have access to the environment of the calling shell. Aliases may be
used to create a mnemonic for a command name, expand a single word to
a complex command, or ensure that a command is called with a basic set
of options.
Arrays
Bash-2.0 supports indexed arrays of unlimited size. The subscript for
an array is an arithmetic expression. Arrays may be assigned to with
a new compound assignment syntax, and several builtins have options to
operate on array variables. Bash includes a number of built-in array
variables.
Arithmetic
Bash allows users to perform integer arithmetic in any base from two
to sixty-four. Nearly all of the C language arithmetic operators are
available with the same syntax and precedence as in C. Arithmetic
expansion allows an arithmetic expression to be evaluated and the
result substituted into the command line. Shell variables can be used
as operands, and the value of an expression may be assigned to a
variable.
An arithmetic expression may be used as a command; the exit status of
the command is the value of the expression.
ANSI-C Quoting
There is a new quoting syntax that allows backslash-escaped characters
in strings to be expanded according to the ANSI C standard.
Tilde Expansion
Users' home directories may be expanded using this feature. Words
beginning with a tilde may also be expanded to the current or previous
working directory.
Brace Expansion
Brace expansion is a convenient way to generate a list of strings that
share a common prefix or suffix.
Substring Capabilities
Bash allows new strings to be created by removing leading or trailing
substrings from existing variable values, or by specifying a starting
offset and length. Portions of variable values may be matched against
shell patterns and the matching portion removed or a new value
substituted.
Indirect Variable Expansion
Bash makes it easy to find the value of a shell variable whose name is
the value of another variable.
Expanded I/O Capabilities
Bash provides several input and output features not available in sh,
including the ability to:
o specify a file or file descriptor for both input and output
o read from or write to asynchronous processes using named pipes
o read lines ending in backslash
o display a prompt on the terminal before a read
o format menus and interpret responses to them
o echo lines exactly as input without escape processing
Control of Builtin Commands
Bash implements several builtin commands to give users more control
over which commands are executed. The enable builtin allows other
builtin commands to be selectively enabled or disabled. The command
and builtin builtins change the order in which the shell searches for
commands.
On systems that provide dynamic loading, new builtins may be loaded
into a running shell from a shared object file. These new builtins
have access to all of the shell facilities.
Help
Bash includes a built-in help facility.
Shell Optional Behavior
There is a great deal of customizable shell behavior. The shopt
builtin command provides a unified interface that allows users to
alter shell defaults.
Prompt Customization
Bash allows the primary and secondary prompts to be customized by
interpreting a number of backslash-escaped special characters.
Parameter and variable expansion is also performed on the values of
the primary and secondary prompt strings before they are displayed.
Security
Bash provides a restricted shell environment. It is also possible to
control the execution of setuid/setgid scripts.
Directory Stack
Bash provides a `directory stack', to which directories may be added
and removed. The current directory may be changed to any directory in
the stack. It is easy to toggle between two directories in the stack.
The directory stack may be saved and restored across different shell
invocations.
POSIX Mode
Bash is nearly completely conformant to POSIX.2. POSIX mode changes
those few areas where the Bash default behavior differs from the
standard to match the standard. In POSIX mode, Bash is POSIX.2
compliant.
Internationalization
Bash provides a new quoting syntax that allows strings to be
translated according to the current locale. The locale in which the
shell itself runs may also be changed, so that the shell messages
themselves may be language-specific.
The command-line editing facilities allow the input of eight-bit
characters, so most of the ISO-8859 family of character sets are
supported.
Command Timing
Bash allows external commands, shell builtin commands and shell functions
to be timed. The format used to display the timing information may be
changed by the user.
0707010007eb34000081a40000000000000000000000015428b7350001850400000100000100b5ffffffffffffffff0000002200000000root/usr/local/share/doc/bash/FAQ This is the Bash FAQ, version 4.13, for Bash version 4.3.
This document contains a set of frequently-asked questions concerning
Bash, the GNU Bourne-Again Shell. Bash is a freely-available command
interpreter with advanced features for both interactive use and shell
programming.
Another good source of basic information about shells is the collection
of FAQ articles periodically posted to comp.unix.shell.
Questions and comments concerning this document should be sent to
chet.ramey@case.edu.
This document is available for anonymous FTP with the URL
ftp://ftp.cwru.edu/pub/bash/FAQ
The Bash home page is http://cnswww.cns.cwru.edu/~chet/bash/bashtop.html
----------
Contents:
Section A: The Basics
A1) What is it?
A2) What's the latest version?
A3) Where can I get it?
A4) On what machines will bash run?
A5) Will bash run on operating systems other than Unix?
A6) How can I build bash with gcc?
A7) How can I make bash my login shell?
A8) I just changed my login shell to bash, and now I can't FTP into my
machine. Why not?
A9) What's the `POSIX Shell and Utilities standard'?
A10) What is the bash `posix mode'?
Section B: The latest version
B1) What's new in version 4.3?
B2) Are there any user-visible incompatibilities between bash-4.3 and
previous bash versions?
Section C: Differences from other Unix shells
C1) How does bash differ from sh, the Bourne shell?
C2) How does bash differ from the Korn shell, version ksh88?
C3) Which new features in ksh-93 are not in bash, and which are?
Section D: Why does bash do some things differently than other Unix shells?
D1) Why does bash run a different version of `command' than
`which command' says it will?
D2) Why doesn't bash treat brace expansions exactly like csh?
D3) Why doesn't bash have csh variable modifiers?
D4) How can I make my csh aliases work when I convert to bash?
D5) How can I pipe standard output and standard error from one command to
another, like csh does with `|&'?
D6) Now that I've converted from ksh to bash, are there equivalents to
ksh features like autoloaded functions and the `whence' command?
Section E: Why does bash do certain things the way it does?
E1) Why is the bash builtin `test' slightly different from /bin/test?
E2) Why does bash sometimes say `Broken pipe'?
E3) When I have terminal escape sequences in my prompt, why does bash
wrap lines at the wrong column?
E4) If I pipe the output of a command into `read variable', why doesn't
the output show up in $variable when the read command finishes?
E5) I have a bunch of shell scripts that use backslash-escaped characters
in arguments to `echo'. Bash doesn't interpret these characters. Why
not, and how can I make it understand them?
E6) Why doesn't a while or for loop get suspended when I type ^Z?
E7) What about empty for loops in Makefiles?
E8) Why does the arithmetic evaluation code complain about `08'?
E9) Why does the pattern matching expression [A-Z]* match files beginning
with every letter except `z'?
E10) Why does `cd //' leave $PWD as `//'?
E11) If I resize my xterm while another program is running, why doesn't bash
notice the change?
E12) Why don't negative offsets in substring expansion work like I expect?
E13) Why does filename completion misbehave if a colon appears in the filename?
E14) Why does quoting the pattern argument to the regular expression matching
conditional operator (=~) cause matching to stop working?
E15) Tell me more about the shell compatibility level.
Section F: Things to watch out for on certain Unix versions
F1) Why can't I use command line editing in my `cmdtool'?
F2) I built bash on Solaris 2. Why do globbing expansions and filename
completion chop off the first few characters of each filename?
F3) Why does bash dump core after I interrupt username completion or
`~user' tilde expansion on a machine running NIS?
F4) I'm running SVR4.2. Why is the line erased every time I type `@'?
F5) Why does bash report syntax errors when my C News scripts use a
redirection before a subshell command?
F6) Why can't I use vi-mode editing on Red Hat Linux 6.1?
F7) Why do bash-2.05a and bash-2.05b fail to compile `printf.def' on
HP/UX 11.x?
Section G: How can I get bash to do certain common things?
G1) How can I get bash to read and display eight-bit characters?
G2) How do I write a function `x' to replace builtin command `x', but
still invoke the command from within the function?
G3) How can I find the value of a shell variable whose name is the value
of another shell variable?
G4) How can I make the bash `time' reserved word print timing output that
looks like the output from my system's /usr/bin/time?
G5) How do I get the current directory into my prompt?
G6) How can I rename "*.foo" to "*.bar"?
G7) How can I translate a filename from uppercase to lowercase?
G8) How can I write a filename expansion (globbing) pattern that will match
all files in the current directory except "." and ".."?
Section H: Where do I go from here?
H1) How do I report bugs in bash, and where should I look for fixes and
advice?
H2) What kind of bash documentation is there?
H3) What's coming in future versions?
H4) What's on the bash `wish list'?
H5) When will the next release appear?
----------
Section A: The Basics
A1) What is it?
Bash is a Unix command interpreter (shell). It is an implementation of
the Posix 1003.2 shell standard, and resembles the Korn and System V
shells.
Bash contains a number of enhancements over those shells, both
for interactive use and shell programming. Features geared
toward interactive use include command line editing, command
history, job control, aliases, and prompt expansion. Programming
features include additional variable expansions, shell
arithmetic, and a number of variables and options to control
shell behavior.
Bash was originally written by Brian Fox of the Free Software
Foundation. The current developer and maintainer is Chet Ramey
of Case Western Reserve University.
A2) What's the latest version?
The latest version is 4.3, first made available on xx December, 2013.
A3) Where can I get it?
Bash is the GNU project's shell, and so is available from the
master GNU archive site, ftp.gnu.org, and its mirrors. The
latest version is also available for FTP from ftp.cwru.edu.
The following URLs tell how to get version 4.3:
ftp://ftp.gnu.org/pub/gnu/bash/bash-4.3.tar.gz
ftp://ftp.cwru.edu/pub/bash/bash-4.3.tar.gz
Formatted versions of the documentation are available with the URLs:
ftp://ftp.gnu.org/pub/gnu/bash/bash-doc-4.3.tar.gz
ftp://ftp.cwru.edu/pub/bash/bash-doc-4.3.tar.gz
Any patches for the current version are available with the URL:
ftp://ftp.cwru.edu/pub/bash/bash-4.3-patches/
A4) On what machines will bash run?
Bash has been ported to nearly every version of Unix. All you
should have to do to build it on a machine for which a port
exists is to type `configure' and then `make'. The build process
will attempt to discover the version of Unix you have and tailor
itself accordingly, using a script created by GNU autoconf.
More information appears in the file `INSTALL' in the distribution.
The Bash web page (http://cnswww.cns.cwru.edu/~chet/bash/bashtop.html)
explains how to obtain binary versions of bash for most of the major
commercial Unix systems.
A5) Will bash run on operating systems other than Unix?
Configuration specifics for Unix-like systems such as QNX and
LynxOS are included in the distribution. Bash-2.05 and later
versions should compile and run on Minix 2.0 (patches were
contributed), but I don't believe anyone has built bash-2.x on
earlier Minix versions yet.
Bash has been ported to versions of Windows implementing the Win32
programming interface. This includes Windows 95 and Windows NT.
The port was done by Cygnus Solutions (now part of Red Hat) as part
of their CYGWIN project. For more information about the project, see
http://www.cygwin.com/.
Cygnus originally ported bash-1.14.7, and that port was part of their
early GNU-Win32 (the original name) releases. Cygnus has also done
ports of bash-3.2 and bash-4.0 to the CYGWIN environment, and both
are available as part of their current release.
Bash-2.05b and later versions should require no local Cygnus changes to
build and run under CYGWIN.
DJ Delorie has a port of bash-2.x which runs under MS-DOS, as part
of the DJGPP project. For more information on the project, see
http://www.delorie.com/djgpp/
I have been told that the original DJGPP port was done by Daisuke Aoyama.
Mark Elbrecht has sent me notice that bash-2.04
is available for DJGPP V2. The files are available as:
ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/bsh204b.zip binary
ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/bsh204d.zip documentation
ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/bsh204s.zip source
Mark began to work with bash-2.05, but I don't know the current status.
Bash-3.0 compiles and runs with no modifications under Microsoft's Services
for Unix (SFU), once known as Interix. I do not anticipate any problems
with building bash-4.2 and later, but will gladly accept any patches that
are needed.
A6) How can I build bash with gcc?
Bash configures to use gcc by default if it is available. Read the
file INSTALL in the distribution for more information.
A7) How can I make bash my login shell?
Some machines let you use `chsh' to change your login shell. Other
systems use `passwd -s' or `passwd -e'. If one of these works for
you, that's all you need. Note that many systems require the full
pathname to a shell to appear in /etc/shells before you can make it
your login shell. For this, you may need the assistance of your
friendly local system administrator.
If you cannot do this, you can still use bash as your login shell, but
you need to perform some tricks. The basic idea is to add a command
to your login shell's startup file to replace your login shell with
bash.
For example, if your login shell is csh or tcsh, and you have installed
bash in /usr/gnu/bin/bash, add the following line to ~/.login:
if ( -f /usr/gnu/bin/bash ) exec /usr/gnu/bin/bash --login
(the `--login' tells bash that it is a login shell).
It's not a good idea to put this command into ~/.cshrc, because every
csh you run without the `-f' option, even ones started to run csh scripts,
reads that file. If you must put the command in ~/.cshrc, use something
like
if ( $?prompt ) exec /usr/gnu/bin/bash --login
to ensure that bash is exec'd only when the csh is interactive.
If your login shell is sh or ksh, you have to do two things.
First, create an empty file in your home directory named `.bash_profile'.
The existence of this file will prevent the exec'd bash from trying to
read ~/.profile, and re-execing itself over and over again. ~/.bash_profile
is the first file bash tries to read initialization commands from when
it is invoked as a login shell.
Next, add a line similar to the above to ~/.profile:
[ -f /usr/gnu/bin/bash ] && [ -x /usr/gnu/bin/bash ] && \
exec /usr/gnu/bin/bash --login
This will cause login shells to replace themselves with bash running as
a login shell. Once you have this working, you can copy your initialization
code from ~/.profile to ~/.bash_profile.
I have received word that the recipe supplied above is insufficient for
machines running CDE. CDE has a maze of twisty little startup files, all
slightly different.
If you cannot change your login shell in the password file to bash, you
will have to (apparently) live with CDE using the shell in the password
file to run its startup scripts. If you have changed your shell to bash,
there is code in the CDE startup files (on Solaris, at least) that attempts
to do the right thing. It is, however, often broken, and may require that
you use the $BASH_ENV trick described below.
`dtterm' claims to use $SHELL as the default program to start, so if you
can change $SHELL in the CDE startup files, you should be able to use bash
in your terminal windows.
Setting DTSOURCEPROFILE in ~/.dtprofile will cause the `Xsession' program
to read your login shell's startup files. You may be able to use bash for
the rest of the CDE programs by setting SHELL to bash in ~/.dtprofile as
well, but I have not tried this.
You can use the above `exec' recipe to start bash when not logging in with
CDE by testing the value of the DT variable:
if [ -n "$DT" ]; then
[ -f /usr/gnu/bin/bash ] && exec /usr/gnu/bin/bash --login
fi
If CDE starts its shells non-interactively during login, the login shell
startup files (~/.profile, ~/.bash_profile) will not be sourced at login.
To get around this problem, append a line similar to the following to your
~/.dtprofile:
BASH_ENV=${HOME}/.bash_profile ; export BASH_ENV
and add the following line to the beginning of ~/.bash_profile:
unset BASH_ENV
A8) I just changed my login shell to bash, and now I can't FTP into my
machine. Why not?
You must add the full pathname to bash to the file /etc/shells. As
noted in the answer to the previous question, many systems require
this before you can make bash your login shell.
Most versions of ftpd use this file to prohibit `special' users
such as `uucp' and `news' from using FTP.
A9) What's the `POSIX Shell and Utilities standard'?
POSIX is a name originally coined by Richard Stallman for a
family of open system standards based on UNIX. There are a
number of aspects of UNIX under consideration for
standardization, from the basic system services at the system
call and C library level to applications and tools to system
administration and management. Each area of standardization is
assigned to a working group in the 1003 series.
The POSIX Shell and Utilities standard was originally developed by
IEEE Working Group 1003.2 (POSIX.2). Today it has been merged with
the original 1003.1 Working Group and is maintained by the Austin
Group (a joint working group of the IEEE, The Open Group and
ISO/IEC SC22/WG15). Today the Shell and Utilities are a volume
within the set of documents that make up IEEE Std 1003.1-2001, and
thus now the former POSIX.2 (from 1992) is now part of the current
POSIX.1 standard (POSIX 1003.1-2001).
The Shell and Utilities volume concentrates on the command
interpreter interface and utility programs commonly executed from
the command line or by other programs. The standard is freely
available on the web at http://www.UNIX-systems.org/version3/ .
Work continues at the Austin Group on maintenance issues; see
http://www.opengroup.org/austin/ to join the discussions.
Bash is concerned with the aspects of the shell's behavior defined
by the POSIX Shell and Utilities volume. The shell command
language has of course been standardized, including the basic flow
control and program execution constructs, I/O redirection and
pipelining, argument handling, variable expansion, and quoting.
The `special' builtins, which must be implemented as part of the
shell to provide the desired functionality, are specified as
being part of the shell; examples of these are `eval' and
`export'. Other utilities appear in the sections of POSIX not
devoted to the shell which are commonly (and in some cases must
be) implemented as builtin commands, such as `read' and `test'.
POSIX also specifies aspects of the shell's interactive
behavior as part of the UPE, including job control and command
line editing. Only vi-style line editing commands have been
standardized; emacs editing commands were left out due to
objections.
The latest version of the POSIX Shell and Utilities standard is
available (now updated to the 2004 Edition) as part of the Single
UNIX Specification Version 3 at
http://www.UNIX-systems.org/version3/
A10) What is the bash `posix mode'?
Although bash is an implementation of the POSIX shell
specification, there are areas where the bash default behavior
differs from that spec. The bash `posix mode' changes the bash
behavior in these areas so that it obeys the spec more closely.
Posix mode is entered by starting bash with the --posix or
'-o posix' option or executing `set -o posix' after bash is running.
The specific aspects of bash which change when posix mode is
active are listed in the file POSIX in the bash distribution.
They are also listed in a section in the Bash Reference Manual
(from which that file is generated).
Section B: The latest version
B1) What's new in version 4.3?
Bash-4.3 is the third revision to the fourth major release of bash.
Bash-4.3 contains the following new features (see the manual page for
complete descriptions and the CHANGES and NEWS files in the bash-4.3
distribution):
o The `helptopic' completion action now maps to all the help topics, not just
the shell builtins.
o The `help' builtin no longer does prefix substring matching first, so
`help read' does not match `readonly', but will do it if exact string
matching fails.
o The shell can be compiled to not display a message about processes that
terminate due to SIGTERM.
o Non-interactive shells now react to the setting of checkwinsize and set
LINES and COLUMNS after a foreground job exits.
o There is a new shell option, `globasciiranges', which, when set to on,
forces globbing range comparisons to use character ordering as if they
were run in the C locale.
o There is a new shell option, `direxpand', which makes filename completion
expand variables in directory names in the way bash-4.1 did.
o In Posix mode, the `command' builtin does not change whether or not a
builtin it shadows is treated as an assignment builtin.
o The `return' and `exit' builtins accept negative exit status arguments.
o The word completion code checks whether or not a filename containing a
shell variable expands to a directory name and appends `/' to the word
as appropriate. The same code expands shell variables in command names
when performing command completion.
o In Posix mode, it is now an error to attempt to define a shell function
with the same name as a Posix special builtin.
o When compiled for strict Posix conformance, history expansion is disabled
by default.
o The history expansion character (!) does not cause history expansion when
followed by the closing quote in a double-quoted string.
o `complete' and its siblings compgen/compopt now takes a new `-o noquote'
option to inhibit quoting of the completions.
o Setting HISTSIZE to a value less than zero causes the history list to be
unlimited (setting it 0 zero disables the history list).
o Setting HISTFILESIZE to a value less than zero causes the history file size
to be unlimited (setting it to 0 causes the history file to be truncated
to zero size).
o The `read' builtin now skips NUL bytes in the input.
o There is a new `bind -X' option to print all key sequences bound to Unix
commands.
o When in Posix mode, `read' is interruptible by a trapped signal. After
running the trap handler, read returns 128+signal and throws away any
partially-read input.
o The command completion code skips whitespace and assignment statements
before looking for the command name word to be completed.
o The build process has a new mechanism for constructing separate help files
that better reflects the current set of compilation options.
o The -nt and -ot options to test now work with files with nanosecond
timestamp resolution.
o The shell saves the command history in any shell for which history is
enabled and HISTFILE is set, not just interactive shells.
o The shell has `nameref' variables and new -n(/+n) options to declare and
unset to use them, and a `test -R' option to test for them.
o The shell now allows assigning, referencing, and unsetting elements of
indexed arrays using negative subscripts (a[-1]=2, echo ${a[-1]}) which
count back from the last element of the array.
o The {x} operators to the [[ conditional command now do string
comparison according to the current locale.
o Programmable completion now uses the completion for `b' instead of `a'
when completion is attempted on a line like: a $(b c.
o Force extglob on temporarily when parsing the pattern argument to
the == and != operators to the [[ command, for compatibility.
o Changed the behavior of interrupting the wait builtin when a SIGCHLD is
received and a trap on SIGCHLD is set to be Posix-mode only.
o The read builtin has a new `-N nchars' option, which reads exactly NCHARS
characters, ignoring delimiters like newline.
o The mapfile/readarray builtin no longer stores the commands it invokes via
callbacks in the history list.
o There is a new `compat40' shopt option.
o The < and > operators to [[ do string comparisons using the current locale
only if the compatibility level is greater than 40 (set to 41 by default).
o New bindable readline function: menu-complete-backward.
o In the readline vi-mode insertion keymap, C-n is now bound to menu-complete
by default, and C-p to menu-complete-backward.
o When in readline vi command mode, repeatedly hitting ESC now does nothing,
even when ESC introduces a bound key sequence. This is closer to how
historical vi behaves.
o New bindable readline function: skip-csi-sequence. Can be used as a
default to consume key sequences generated by keys like Home and End
without having to bind all keys.
o New bindable readline variable: skip-completed-text, active when
completing in the middle of a word. If enabled, it means that characters
in the completion that match characters in the remainder of the word are
"skipped" rather than inserted into the line.
o The pre-readline-6.0 version of menu completion is available as
"old-menu-complete" for users who do not like the readline-6.0 version.
o New bindable readline variable: echo-control-characters. If enabled, and
the tty ECHOCTL bit is set, controls the echoing of characters
corresponding to keyboard-generated signals.
o New bindable readline variable: enable-meta-key. Controls whether or not
readline sends the smm/rmm sequences if the terminal indicates it has a
meta key that enables eight-bit characters.
Bash-4.0 contained the following new features:
o When using substring expansion on the positional parameters, a starting
index of 0 now causes $0 to be prefixed to the list.
o There is a new variable, $BASHPID, which always returns the process id of
the current shell.
o There is a new `autocd' option that, when enabled, causes bash to attempt
to `cd' to a directory name that is supplied as the first word of a
simple command.
o There is a new `checkjobs' option that causes the shell to check for and
report any running or stopped jobs at exit.
o The programmable completion code exports a new COMP_TYPE variable, set to
a character describing the type of completion being attempted.
o The programmable completion code exports a new COMP_KEY variable, set to
the character that caused the completion to be invoked (e.g., TAB).
o The programmable completion code now uses the same set of characters as
readline when breaking the command line into a list of words.
o The block multiplier for the ulimit -c and -f options is now 512 when in
Posix mode, as Posix specifies.
o Changed the behavior of the read builtin to save any partial input received
in the specified variable when the read builtin times out. This also
results in variables specified as arguments to read to be set to the empty
string when there is no input available. When the read builtin times out,
it returns an exit status greater than 128.
o The shell now has the notion of a `compatibility level', controlled by
new variables settable by `shopt'. Setting this variable currently
restores the bash-3.1 behavior when processing quoted strings on the rhs
of the `=~' operator to the `[[' command.
o The `ulimit' builtin now has new -b (socket buffer size) and -T (number
of threads) options.
o There is a new `compopt' builtin that allows completion functions to modify
completion options for existing completions or the completion currently
being executed.
o The `read' builtin has a new -i option which inserts text into the reply
buffer when using readline.
o A new `-E' option to the complete builtin allows control of the default
behavior for completion on an empty line.
o There is now limited support for completing command name words containing
globbing characters.
o The `help' builtin now has a new -d option, to display a short description,
and a -m option, to print help information in a man page-like format.
o There is a new `mapfile' builtin to populate an array with lines from a
given file.
o If a command is not found, the shell attempts to execute a shell function
named `command_not_found_handle', supplying the command words as the
function arguments.
o There is a new shell option: `globstar'. When enabled, the globbing code
treats `**' specially -- it matches all directories (and files within
them, when appropriate) recursively.
o There is a new shell option: `dirspell'. When enabled, the filename
completion code performs spelling correction on directory names during
completion.
o The `-t' option to the `read' builtin now supports fractional timeout
values.
o Brace expansion now allows zero-padding of expanded numeric values and
will add the proper number of zeroes to make sure all values contain the
same number of digits.
o There is a new bash-specific bindable readline function: `dabbrev-expand'.
It uses menu completion on a set of words taken from the history list.
o The command assigned to a key sequence with `bind -x' now sets two new
variables in the environment of the executed command: READLINE_LINE_BUFFER
and READLINE_POINT. The command can change the current readline line
and cursor position by modifying READLINE_LINE_BUFFER and READLINE_POINT,
respectively.
o There is a new >>& redirection operator, which appends the standard output
and standard error to the named file.
o The parser now understands `|&' as a synonym for `2>&1 |', which redirects
the standard error for a command through a pipe.
o The new `;&' case statement action list terminator causes execution to
continue with the action associated with the next pattern in the
statement rather than terminating the command.
o The new `;;&' case statement action list terminator causes the shell to
test the next set of patterns after completing execution of the current
action, rather than terminating the command.
o The shell understands a new variable: PROMPT_DIRTRIM. When set to an
integer value greater than zero, prompt expansion of \w and \W will
retain only that number of trailing pathname components and replace
the intervening characters with `...'.
o There are new case-modifying word expansions: uppercase (^[^]) and
lowercase (,[,]). They can work on either the first character or
array element, or globally. They accept an optional shell pattern
that determines which characters to modify. There is an optionally-
configured feature to include capitalization operators.
o The shell provides associative array variables, with the appropriate
support to create, delete, assign values to, and expand them.
o The `declare' builtin now has new -l (convert value to lowercase upon
assignment) and -u (convert value to uppercase upon assignment) options.
There is an optionally-configurable -c option to capitalize a value at
assignment.
o There is a new `coproc' reserved word that specifies a coprocess: an
asynchronous command run with two pipes connected to the creating shell.
Coprocs can be named. The input and output file descriptors and the
PID of the coprocess are available to the calling shell in variables
with coproc-specific names.
o A value of 0 for the -t option to `read' now returns success if there is
input available to be read from the specified file descriptor.
o CDPATH and GLOBIGNORE are ignored when the shell is running in privileged
mode.
o New bindable readline functions shell-forward-word and shell-backward-word,
which move forward and backward words delimited by shell metacharacters
and honor shell quoting.
o New bindable readline functions shell-backward-kill-word and shell-kill-word
which kill words backward and forward, but use the same word boundaries
as shell-forward-word and shell-backward-word.
Bash-3.2 contained the following new features:
o Bash-3.2 now checks shell scripts for NUL characters rather than non-printing
characters when deciding whether or not a script is a binary file.
o Quoting the string argument to the [[ command's =~ (regexp) operator now
forces string matching, as with the other pattern-matching operators.
Bash-3.1 contained the following new features:
o Bash-3.1 may now be configured and built in a mode that enforces strict
POSIX compliance.
o The `+=' assignment operator, which appends to the value of a string or
array variable, has been implemented.
o It is now possible to ignore case when matching in contexts other than
filename generation using the new `nocasematch' shell option.
Bash-3.0 contained the following new features:
o Features to support the bash debugger have been implemented, and there
is a new `extdebug' option to turn the non-default options on
o HISTCONTROL is now a colon-separated list of options and has been
extended with a new `erasedups' option that will result in only one
copy of a command being kept in the history list
o Brace expansion has been extended with a new {x..y} form, producing
sequences of digits or characters
o Timestamps are now kept with history entries, with an option to save
and restore them from the history file; there is a new HISTTIMEFORMAT
variable describing how to display the timestamps when listing history
entries
o The `[[' command can now perform extended regular expression (egrep-like)
matching, with matched subexpressions placed in the BASH_REMATCH array
variable
o A new `pipefail' option causes a pipeline to return a failure status if
any command in it fails
o The `jobs', `kill', and `wait' builtins now accept job control notation
in their arguments even if job control is not enabled
o The `gettext' package and libintl have been integrated, and the shell
messages may be translated into other languages
Bash-2.05b introduced the following new features:
o support for multibyte characters has been added to both bash and readline
o the DEBUG trap is now run *before* simple commands, ((...)) commands,
[[...]] conditional commands, and for ((...)) loops
o the shell now performs arithmetic in the largest integer size the machine
supports (intmax_t)
o there is a new \D{...} prompt expansion; passes the `...' to strftime(3)
and inserts the result into the expanded prompt
o there is a new `here-string' redirection operator: <<< word
o when displaying variables, function attributes and definitions are shown
separately, allowing them to be re-used as input (attempting to re-use
the old output would result in syntax errors).
o `read' has a new `-u fd' option to read from a specified file descriptor
o the bash debugger in examples/bashdb has been modified to work with the
new DEBUG trap semantics, the command set has been made more gdb-like,
and the changes to $LINENO make debugging functions work better
o the expansion of $LINENO inside a shell function is only relative to the
function start if the shell is interactive -- if the shell is running a
script, $LINENO expands to the line number in the script. This is as
POSIX-2001 requires
Bash-2.05a introduced the following new features:
o The `printf' builtin has undergone major work
o There is a new read-only `shopt' option: login_shell, which is set by
login shells and unset otherwise
o New `\A' prompt string escape sequence; expanding to time in 24-hour
HH:MM format
o New `-A group/-g' option to complete and compgen; goes group name
completion
o New [+-]O invocation option to set and unset `shopt' options at startup
o ksh-like `ERR' trap
o `for' loops now allow empty word lists after the `in' reserved word
o new `hard' and `soft' arguments for the `ulimit' builtin
o Readline can be configured to place the user at the same point on the line
when retrieving commands from the history list
o Readline can be configured to skip `hidden' files (filenames with a leading
`.' on Unix) when performing completion
Bash-2.05 introduced the following new features:
o This version has once again reverted to using locales and strcoll(3) when
processing pattern matching bracket expressions, as POSIX requires.
o Added a new `--init-file' invocation argument as a synonym for `--rcfile',
per the new GNU coding standards.
o The /dev/tcp and /dev/udp redirections now accept service names as well as
port numbers.
o `complete' and `compgen' now take a `-o value' option, which controls some
of the aspects of that compspec. Valid values are:
default - perform bash default completion if programmable
completion produces no matches
dirnames - perform directory name completion if programmable
completion produces no matches
filenames - tell readline that the compspec produces filenames,
so it can do things like append slashes to
directory names and suppress trailing spaces
o A new loadable builtin, realpath, which canonicalizes and expands symlinks
in pathname arguments.
o When `set' is called without options, it prints function defintions in a
way that allows them to be reused as input. This affects `declare' and
`declare -p' as well. This only happens when the shell is not in POSIX
mode, since POSIX.2 forbids this behavior.
Bash-2.04 introduced the following new features:
o Programmable word completion with the new `complete' and `compgen' builtins;
examples are provided in examples/complete/complete-examples
o `history' has a new `-d' option to delete a history entry
o `bind' has a new `-x' option to bind key sequences to shell commands
o The prompt expansion code has new `\j' and `\l' escape sequences
o The `no_empty_cmd_completion' shell option, if enabled, inhibits
command completion when TAB is typed on an empty line
o `help' has a new `-s' option to print a usage synopsis
o New arithmetic operators: var++, var--, ++var, --var, expr1,expr2 (comma)
o New ksh93-style arithmetic for command:
for ((expr1 ; expr2; expr3 )); do list; done
o `read' has new options: `-t', `-n', `-d', `-s'
o The redirection code handles several filenames specially: /dev/fd/N,
/dev/stdin, /dev/stdout, /dev/stderr
o The redirection code now recognizes /dev/tcp/HOST/PORT and
/dev/udp/HOST/PORT and tries to open a TCP or UDP socket, respectively,
to the specified port on the specified host
o The ${!prefix*} expansion has been implemented
o A new FUNCNAME variable, which expands to the name of a currently-executing
function
o The GROUPS variable is no longer readonly
o A new shopt `xpg_echo' variable, to control the behavior of echo with
respect to backslash-escape sequences at runtime
o The NON_INTERACTIVE_LOGIN_SHELLS #define has returned
The version of Readline released with Bash-2.04, Readline-4.1, had several
new features as well:
o Parentheses matching is always compiled into readline, and controllable
with the new `blink-matching-paren' variable
o The history-search-forward and history-search-backward functions now leave
point at the end of the line when the search string is empty, like
reverse-search-history, and forward-search-history
o A new function for applications: rl_on_new_line_with_prompt()
o New variables for applications: rl_already_prompted, and rl_gnu_readline_p
Bash-2.03 had very few new features, in keeping with the convention
that odd-numbered releases provide mainly bug fixes. A number of new
features were added to Readline, mostly at the request of the Cygnus
folks.
A new shopt option, `restricted_shell', so that startup files can test
whether or not the shell was started in restricted mode
Filename generation is now performed on the words between ( and ) in
compound array assignments (this is really a bug fix)
OLDPWD is now auto-exported, as POSIX.2 requires
ENV and BASH_ENV are read-only variables in a restricted shell
Bash may now be linked against an already-installed Readline library,
as long as the Readline library is version 4 or newer
All shells begun with the `--login' option will source the login shell
startup files, even if the shell is not interactive
There were lots of changes to the version of the Readline library released
along with Bash-2.03. For a complete list of the changes, read the file
CHANGES in the Bash-2.03 distribution.
Bash-2.02 contained the following new features:
a new version of malloc (based on the old GNU malloc code in previous
bash versions) that is more page-oriented, more conservative
with memory usage, does not `orphan' large blocks when they
are freed, is usable on 64-bit machines, and has allocation
checking turned on unconditionally
POSIX.2-style globbing character classes ([:alpha:], [:alnum:], etc.)
POSIX.2-style globbing equivalence classes
POSIX.2-style globbing collating symbols
the ksh [[...]] extended conditional command
the ksh egrep-style extended pattern matching operators
a new `printf' builtin
the ksh-like $(, &>, >|, <<<, [n]<&word-, [n]>&word-, >>&
prompt string special char translation and variable expansion
auto-export of variables in initial environment
command search finds functions before builtins
bash return builtin will exit a file sourced with `.'
builtins: cd -/-L/-P/-@, exec -l/-c/-a, echo -e/-E, hash -d/-l/-p/-t.
export -n/-f/-p/name=value, pwd -L/-P,
read -e/-p/-a/-t/-n/-d/-s/-u/-i/-N,
readonly -a/-f/name=value, trap -l, set +o,
set -b/-m/-o option/-h/-p/-B/-C/-H/-P,
unset -f/-n/-v, ulimit -i/-m/-p/-q/-u/-x,
type -a/-p/-t/-f/-P, suspend -f, kill -n,
test -o optname/s1 == s2/s1 < s2/s1 > s2/-nt/-ot/-ef/-O/-G/-S/-R
bash reads ~/.bashrc for interactive shells, $ENV for non-interactive
bash restricted shell mode is more extensive
bash allows functions and variables with the same name
brace expansion
tilde expansion
arithmetic expansion with $((...)) and `let' builtin
the `[[...]]' extended conditional command
process substitution
aliases and alias/unalias builtins
local variables in functions and `local' builtin
readline and command-line editing with programmable completion
command history and history/fc builtins
csh-like history expansion
other new bash builtins: bind, command, compgen, complete, builtin,
declare/typeset, dirs, enable, fc, help,
history, logout, popd, pushd, disown, shopt,
printf, compopt, mapfile
exported functions
filename generation when using output redirection (command >a*)
POSIX.2-style globbing character classes
POSIX.2-style globbing equivalence classes
POSIX.2-style globbing collating symbols
egrep-like extended pattern matching operators
case-insensitive pattern matching and globbing
variable assignments preceding commands affect only that command,
even for builtins and functions
posix mode and strict posix conformance
redirection to /dev/fd/N, /dev/stdin, /dev/stdout, /dev/stderr,
/dev/tcp/host/port, /dev/udp/host/port
debugger support, including `caller' builtin and new variables
RETURN trap
the `+=' assignment operator
autocd shell option and behavior
command-not-found hook with command_not_found_handle shell function
globstar shell option and `**' globbing behavior
|& synonym for `2>&1 |'
;& and ;;& case action list terminators
case-modifying word expansions and variable attributes
associative arrays
coprocesses using the `coproc' reserved word and variables
shell assignment of a file descriptor used in a redirection to a variable
Things sh has that bash does not:
uses variable SHACCT to do shell accounting
includes `stop' builtin (bash can use alias stop='kill -s STOP')
`newgrp' builtin
turns on job control if called as `jsh'
$TIMEOUT (like bash $TMOUT)
`^' is a synonym for `|'
new SVR4.2 sh builtins: mldmode, priv
Implementation differences:
redirection to/from compound commands causes sh to create a subshell
bash does not allow unbalanced quotes; sh silently inserts them at EOF
bash does not mess with signal 11
sh sets (euid, egid) to (uid, gid) if -p not supplied and uid < 100
bash splits only the results of expansions on IFS, using POSIX.2
field splitting rules; sh splits all words on IFS
sh does not allow MAILCHECK to be unset (?)
sh does not allow traps on SIGALRM or SIGCHLD
bash allows multiple option arguments when invoked (e.g. -x -v);
sh allows only a single option argument (`sh -x -v' attempts
to open a file named `-v', and, on SunOS 4.1.4, dumps core.
On Solaris 2.4 and earlier versions, sh goes into an infinite
loop.)
sh exits a script if any builtin fails; bash exits only if one of
the POSIX.2 `special' builtins fails
C2) How does bash differ from the Korn shell, version ksh88?
Things bash has or uses that ksh88 does not:
long invocation options
[-+]O invocation option
-l invocation option
`!' reserved word
arithmetic for command: for ((expr1 ; expr2; expr3 )); do list; done
arithmetic in largest machine-supported size (intmax_t)
posix mode and posix conformance
command hashing
tilde expansion for assignment statements that look like $PATH
process substitution with named pipes if /dev/fd is not available
the ${!param} indirect parameter expansion operator
the ${!param*} prefix expansion operator
the ${param:offset[:length]} parameter substring operator
the ${param/pat[/string]} parameter pattern substitution operator
variables: BASH, BASH_VERSION, BASH_VERSINFO, BASHPID, UID, EUID, SHLVL,
TIMEFORMAT, HISTCMD, HOSTTYPE, OSTYPE, MACHTYPE,
HISTFILESIZE, HISTIGNORE, HISTCONTROL, PROMPT_COMMAND,
IGNOREEOF, FIGNORE, INPUTRC, HOSTFILE, DIRSTACK,
PIPESTATUS, HOSTNAME, OPTERR, SHELLOPTS, GLOBIGNORE,
GROUPS, FUNCNAME, histchars, auto_resume, PROMPT_DIRTRIM
prompt expansion with backslash escapes and command substitution
redirection: &> (stdout and stderr), <<<, [n]<&word-, [n]>&word-, >>&
more extensive and extensible editing and programmable completion
builtins: bind, builtin, command, declare, dirs, echo -e/-E, enable,
exec -l/-c/-a, fc -s, export -n/-f/-p, hash, help, history,
jobs -x/-r/-s, kill -s/-n/-l, local, logout, popd, pushd,
read -e/-p/-a/-t/-n/-d/-s/-N, readonly -a/-n/-f/-p,
set -o braceexpand/-o histexpand/-o interactive-comments/
-o notify/-o physical/-o posix/-o hashall/-o onecmd/
-h/-B/-C/-b/-H/-P, set +o, suspend, trap -l, type,
typeset -a/-F/-p, ulimit -i/-q/-u/-x, umask -S, alias -p,
shopt, disown, printf, complete, compgen, compopt, mapfile
`!' csh-style history expansion
POSIX.2-style globbing character classes
POSIX.2-style globbing equivalence classes
POSIX.2-style globbing collating symbols
egrep-like extended pattern matching operators
case-insensitive pattern matching and globbing
`**' arithmetic operator to do exponentiation
redirection to /dev/fd/N, /dev/stdin, /dev/stdout, /dev/stderr
arrays of unlimited size
TMOUT is default timeout for `read' and `select'
debugger support, including the `caller' builtin
RETURN trap
Timestamps in history entries
{x..y} brace expansion
The `+=' assignment operator
autocd shell option and behavior
command-not-found hook with command_not_found_handle shell function
globstar shell option and `**' globbing behavior
|& synonym for `2>&1 |'
;& and ;;& case action list terminators
case-modifying word expansions and variable attributes
associative arrays
coprocesses using the `coproc' reserved word and variables
shell assignment of a file descriptor used in a redirection to a variable
Things ksh88 has or uses that bash does not:
tracked aliases (alias -t)
variables: ERRNO, FPATH, EDITOR, VISUAL
co-processes (bash uses different syntax)
weirdly-scoped functions
typeset +f to list all function names without definitions
text of command history kept in a file, not memory
builtins: alias -x, cd old new, newgrp, print,
read -p/-s/var?prompt, set -A/-o gmacs/
-o bgnice/-o markdirs/-o trackall/-o viraw/-s,
typeset -H/-L/-R/-Z/-A/-ft/-fu/-fx/-t, whence
using environment to pass attributes of exported variables
arithmetic evaluation done on arguments to some builtins
reads .profile from $PWD when invoked as login shell
Implementation differences:
ksh runs last command of a pipeline in parent shell context
bash has brace expansion by default (ksh88 compile-time option)
bash has fixed startup file for all interactive shells; ksh reads $ENV
bash has exported functions
bash command search finds functions before builtins
bash waits for all commands in pipeline to exit before returning status
emacs-mode editing has some slightly different key bindings
C3) Which new features in ksh-93 are not in bash, and which are?
This list is current through ksh93v (10/08/2013)
New things in ksh-93 not in bash-4.3:
floating point arithmetic, variables, and constants
math library functions, including user-defined math functions
${!name[sub]} name of subscript for associative array
`.' is allowed in variable names to create a hierarchical namespace
more extensive compound assignment syntax
discipline functions
KEYBD trap
variables: .sh.edchar, .sh.edmode, .sh.edcol, .sh.edtext, .sh.version,
.sh.name, .sh.subscript, .sh.value, .sh.match, HISTEDIT,
.sh.sig, .sh.stats, .sh.siginfo, .sh.pwdfd, .sh.op_astbin,
.sh.pool
backreferences in pattern matching (\N)
`&' operator in pattern lists for matching (match all instead of any)
exit statuses between 0 and 255
FPATH and PATH mixing
lexical scoping for local variables in `ksh' functions
no scoping for local variables in `POSIX' functions
$'' \C[.collating-element.] escape sequence
-C/-I invocation options
print -f (bash uses printf) and rest of print builtin options
printf %(type)q, %#q
`fc' has been renamed to `hist'
`.' can execute shell functions
getopts -a
printf %B, %H, %P, %R, %Z modifiers, output base for %d, `=' flag
read -n/-N differ/-v/-S
set -o showme/-o multiline (bash default)
set -K
kill -Q/-q/-L
trap -a
`sleep' and `getconf' builtins (bash has loadable versions)
[[ -R name ]] (checks whether or not name is a nameref)
typeset -C/-S/-T/-X/-h/-s/-c/-M
experimental `type' definitions (a la typedef) using typeset
array expansions ${array[sub1..sub2]} and ${!array[sub1..sub2]}
associative array assignments using `;' as element separator
command substitution $(n<#) expands to current byte offset for fd N
new '${ ' form of command substitution, executed in current shell
new >;/<>;/<#pat/<##pat/<#/># redirections
brace expansion printf-like formats
CHLD trap triggered by SIGSTOP and SIGCONT
~{fd} expansion, which replaces fd with the corresponding path name
$"string" expanded when referenced rather than when first parsed
job "pools", which allow a collection of jobs to be managed as a unit
New things in ksh-93 present in bash-4.3:
associative arrays
[n]<&word- and [n]>&word- redirections (combination dup and close)
for (( expr1; expr2; expr3 )) ; do list; done - arithmetic for command
?:, ++, --, `expr1 , expr2' arithmetic operators
expansions: ${!param}, ${param:offset[:len]}, ${param/pat[/str]},
${!param*}
compound array assignment
negative subscripts for indexed array variables
the `!' reserved word
loadable builtins -- but ksh uses `builtin' while bash uses `enable'
new $'...' and $"..." quoting
FIGNORE (but bash uses GLOBIGNORE), HISTCMD
brace expansion and set -B
changes to kill builtin
`command', `builtin', `disown' builtins
echo -e
exec -c/-a
printf %T modifier
read -A (bash uses read -a)
read -t/-d
trap -p
`.' restores the positional parameters when it completes
set -o notify/-C
set -o pipefail
set -G (-o globstar) and **
POSIX.2 `test'
umask -S
unalias -a
command and arithmetic substitution performed on PS1, PS4, and ENV
command name completion, TAB displaying possible completions
ENV processed only for interactive shells
The `+=' assignment operator
the `;&' case statement "fallthrough" pattern list terminator
csh-style history expansion and set -H
negative offsets in ${param:offset:length}
redirection operators preceded with {varname} to store fd number in varname
DEBUG can force skipping following command
[[ -v var ]] operator (checks whether or not var is set)
typeset -n and `nameref' variables
process substitutions work without /dev/fd
Section D: Why does bash do some things differently than other Unix shells?
D1) Why does bash run a different version of `command' than
`which command' says it will?
On many systems, `which' is actually a csh script that assumes
you're running csh. In tcsh, `which' and its cousin `where'
are builtins. On other Unix systems, `which' is a perl script
that uses the PATH environment variable. Many Linux distributions
use GNU `which', which is a C program that can understand shell
aliases.
The csh script version reads the csh startup files from your
home directory and uses those to determine which `command' will
be invoked. Since bash doesn't use any of those startup files,
there's a good chance that your bash environment differs from
your csh environment. The bash `type' builtin does everything
`which' does, and will report correct results for the running
shell. If you're really wedded to the name `which', try adding
the following function definition to your .bashrc:
which()
{
builtin type "$@"
}
If you're moving from tcsh and would like to bring `where' along
as well, use this function:
where()
{
builtin type -a "$@"
}
D2) Why doesn't bash treat brace expansions exactly like csh?
The only difference between bash and csh brace expansion is that
bash requires a brace expression to contain at least one unquoted
comma if it is to be expanded. Any brace-surrounded word not
containing an unquoted comma is left unchanged by the brace
expansion code. This affords the greatest degree of sh
compatibility.
Bash, ksh, zsh, and pd-ksh all implement brace expansion this way.
D3) Why doesn't bash have csh variable modifiers?
Posix has specified a more powerful, albeit somewhat more cryptic,
mechanism cribbed from ksh, and bash implements it.
${parameter%word}
Remove smallest suffix pattern. The WORD is expanded to produce
a pattern. It then expands to the value of PARAMETER, with the
smallest portion of the suffix matched by the pattern deleted.
x=file.c
echo ${x%.c}.o
-->file.o
${parameter%%word}
Remove largest suffix pattern. The WORD is expanded to produce
a pattern. It then expands to the value of PARAMETER, with the
largest portion of the suffix matched by the pattern deleted.
x=posix/src/std
echo ${x%%/*}
-->posix
${parameter#word}
Remove smallest prefix pattern. The WORD is expanded to produce
a pattern. It then expands to the value of PARAMETER, with the
smallest portion of the prefix matched by the pattern deleted.
x=$HOME/src/cmd
echo ${x#$HOME}
-->/src/cmd
${parameter##word}
Remove largest prefix pattern. The WORD is expanded to produce
a pattern. It then expands to the value of PARAMETER, with the
largest portion of the prefix matched by the pattern deleted.
x=/one/two/three
echo ${x##*/}
-->three
Given
a=/a/b/c/d
b=b.xxx
csh bash result
--- ---- ------
$a:h ${a%/*} /a/b/c
$a:t ${a##*/} d
$b:r ${b%.*} b
$b:e ${b##*.} xxx
D4) How can I make my csh aliases work when I convert to bash?
Bash uses a different syntax to support aliases than csh does.
The details can be found in the documentation. We have provided
a shell script which does most of the work of conversion for you;
this script can be found in ./examples/misc/aliasconv.sh. Here is
how you use it:
Start csh in the normal way for you. (e.g., `csh')
Pipe the output of `alias' through `aliasconv.sh', saving the
results into `bash_aliases':
alias | bash aliasconv.sh >bash_aliases
Edit `bash_aliases', carefully reading through any created
functions. You will need to change the names of some csh specific
variables to the bash equivalents. The script converts $cwd to
$PWD, $term to $TERM, $home to $HOME, $user to $USER, and $prompt
to $PS1. You may also have to add quotes to avoid unwanted
expansion.
For example, the csh alias:
alias cd 'cd \!*; echo $cwd'
is converted to the bash function:
cd () { command cd "$@"; echo $PWD ; }
The only thing that needs to be done is to quote $PWD:
cd () { command cd "$@"; echo "$PWD" ; }
Merge the edited file into your ~/.bashrc.
There is an additional, more ambitious, script in
examples/misc/cshtobash that attempts to convert your entire csh
environment to its bash equivalent. This script can be run as
simply `cshtobash' to convert your normal interactive
environment, or as `cshtobash ~/.login' to convert your login
environment.
D5) How can I pipe standard output and standard error from one command to
another, like csh does with `|&'?
Use
command 2>&1 | command2
The key is to remember that piping is performed before redirection, so
file descriptor 1 points to the pipe when it is duplicated onto file
descriptor 2.
D6) Now that I've converted from ksh to bash, are there equivalents to
ksh features like autoloaded functions and the `whence' command?
There are features in ksh-88 and ksh-93 that do not have direct bash
equivalents. Most, however, can be emulated with very little trouble.
ksh-88 feature Bash equivalent
-------------- ---------------
compiled-in aliases set up aliases in .bashrc; some ksh aliases are
bash builtins (hash, history, type)
coprocesses named pipe pairs (one for read, one for write)
typeset +f declare -F
cd, print, whence function substitutes in examples/functions/kshenv
autoloaded functions examples/functions/autoload is the same as typeset -fu
read var?prompt read -p prompt var
ksh-93 feature Bash equivalent
-------------- ---------------
sleep, getconf Bash has loadable versions in examples/loadables
${.sh.version} $BASH_VERSION
print -f printf
hist alias hist=fc
$HISTEDIT $FCEDIT
Section E: How can I get bash to do certain things, and why does bash do
things the way it does?
E1) Why is the bash builtin `test' slightly different from /bin/test?
The specific example used here is [ ! x -o x ], which is false.
Bash's builtin `test' implements the Posix.2 spec, which can be
summarized as follows (the wording is due to David Korn):
Here is the set of rules for processing test arguments.
0 Args: False
1 Arg: True iff argument is not null.
2 Args: If first arg is !, True iff second argument is null.
If first argument is unary, then true if unary test is true
Otherwise error.
3 Args: If second argument is a binary operator, do binary test of $1 $3
If first argument is !, negate two argument test of $2 $3
If first argument is `(' and third argument is `)', do the
one-argument test of the second argument.
Otherwise error.
4 Args: If first argument is !, negate three argument test of $2 $3 $4.
Otherwise unspecified
5 or more Args: unspecified. (Historical shells would use their
current algorithm).
The operators -a and -o are considered binary operators for the purpose
of the 3 Arg case.
As you can see, the test becomes (not (x or x)), which is false.
E2) Why does bash sometimes say `Broken pipe'?
If a sequence of commands appears in a pipeline, and one of the
reading commands finishes before the writer has finished, the
writer receives a SIGPIPE signal. Many other shells special-case
SIGPIPE as an exit status in the pipeline and do not report it.
For example, in:
ps -aux | head
`head' can finish before `ps' writes all of its output, and ps
will try to write on a pipe without a reader. In that case, bash
will print `Broken pipe' to stderr when ps is killed by a
SIGPIPE.
As of bash-3.1, bash does not report SIGPIPE errors by default. You
can build a version of bash that will report such errors.
E3) When I have terminal escape sequences in my prompt, why does bash
wrap lines at the wrong column?
Readline, the line editing library that bash uses, does not know
that the terminal escape sequences do not take up space on the
screen. The redisplay code assumes, unless told otherwise, that
each character in the prompt is a `printable' character that
takes up one character position on the screen.
You can use the bash prompt expansion facility (see the PROMPTING
section in the manual page) to tell readline that sequences of
characters in the prompt strings take up no screen space.
Use the \[ escape to begin a sequence of non-printing characters,
and the \] escape to signal the end of such a sequence.
E4) If I pipe the output of a command into `read variable', why doesn't
the output show up in $variable when the read command finishes?
This has to do with the parent-child relationship between Unix
processes. It affects all commands run in pipelines, not just
simple calls to `read'. For example, piping a command's output
into a `while' loop that repeatedly calls `read' will result in
the same behavior.
Each element of a pipeline, even a builtin or shell function,
runs in a separate process, a child of the shell running the
pipeline. A subprocess cannot affect its parent's environment.
When the `read' command sets the variable to the input, that
variable is set only in the subshell, not the parent shell. When
the subshell exits, the value of the variable is lost.
Many pipelines that end with `read variable' can be converted
into command substitutions, which will capture the output of
a specified command. The output can then be assigned to a
variable:
grep ^gnu /usr/lib/news/active | wc -l | read ngroup
can be converted into
ngroup=$(grep ^gnu /usr/lib/news/active | wc -l)
This does not, unfortunately, work to split the text among
multiple variables, as read does when given multiple variable
arguments. If you need to do this, you can either use the
command substitution above to read the output into a variable
and chop up the variable using the bash pattern removal
expansion operators or use some variant of the following
approach.
Say /usr/local/bin/ipaddr is the following shell script:
#! /bin/sh
host `hostname` | awk '/address/ {print $NF}'
Instead of using
/usr/local/bin/ipaddr | read A B C D
to break the local machine's IP address into separate octets, use
OIFS="$IFS"
IFS=.
set -- $(/usr/local/bin/ipaddr)
IFS="$OIFS"
A="$1" B="$2" C="$3" D="$4"
Beware, however, that this will change the shell's positional
parameters. If you need them, you should save them before doing
this.
This is the general approach -- in most cases you will not need to
set $IFS to a different value.
Some other user-supplied alternatives include:
read A B C D << HERE
$(IFS=.; echo $(/usr/local/bin/ipaddr))
HERE
and, where process substitution is available,
read A B C D < <(IFS=.; echo $(/usr/local/bin/ipaddr))
E5) I have a bunch of shell scripts that use backslash-escaped characters
in arguments to `echo'. Bash doesn't interpret these characters. Why
not, and how can I make it understand them?
This is the behavior of echo on most Unix System V machines.
The bash builtin `echo' is modeled after the 9th Edition
Research Unix version of `echo'. It does not interpret
backslash-escaped characters in its argument strings by default;
it requires the use of the -e option to enable the
interpretation. The System V echo provides no way to disable the
special characters; the bash echo has a -E option to disable
them.
There is a configuration option that will make bash behave like
the System V echo and interpret things like `\t' by default. Run
configure with the --enable-xpg-echo-default option to turn this
on. Be aware that this will cause some of the tests run when you
type `make tests' to fail.
There is a shell option, `xpg_echo', settable with `shopt', that will
change the behavior of echo at runtime. Enabling this option turns
on expansion of backslash-escape sequences.
E6) Why doesn't a while or for loop get suspended when I type ^Z?
This is a consequence of how job control works on Unix. The only
thing that can be suspended is the process group. This is a single
command or pipeline of commands that the shell forks and executes.
When you run a while or for loop, the only thing that the shell forks
and executes are any commands in the while loop test and commands in
the loop bodies. These, therefore, are the only things that can be
suspended when you type ^Z.
If you want to be able to stop the entire loop, you need to put it
within parentheses, which will force the loop into a subshell that
may be stopped (and subsequently restarted) as a single unit.
E7) What about empty for loops in Makefiles?
It's fairly common to see constructs like this in automatically-generated
Makefiles:
SUBDIRS = @SUBDIRS@
...
subdirs-clean:
for d in ${SUBDIRS}; do \
( cd $$d && ${MAKE} ${MFLAGS} clean ) \
done
When SUBDIRS is empty, this results in a command like this being passed to
bash:
for d in ; do
( cd $d && ${MAKE} ${MFLAGS} clean )
done
In versions of bash before bash-2.05a, this was a syntax error. If the
reserved word `in' was present, a word must follow it before the semicolon
or newline. The language in the manual page referring to the list of words
being empty referred to the list after it is expanded. These versions of
bash required that there be at least one word following the `in' when the
construct was parsed.
The idiomatic Makefile solution is something like:
SUBDIRS = @SUBDIRS@
subdirs-clean:
subdirs=$SUBDIRS ; for d in $$subdirs; do \
( cd $$d && ${MAKE} ${MFLAGS} clean ) \
done
The latest updated POSIX standard has changed this: the word list
is no longer required. Bash versions 2.05a and later accept the
new syntax.
E8) Why does the arithmetic evaluation code complain about `08'?
The bash arithmetic evaluation code (used for `let', $(()), (()), and in
other places), interprets a leading `0' in numeric constants as denoting
an octal number, and a leading `0x' as denoting hexadecimal. This is
in accordance with the POSIX.2 spec, section 2.9.2.1, which states that
arithmetic constants should be handled as signed long integers as defined
by the ANSI/ISO C standard.
The POSIX.2 interpretation committee has confirmed this:
http://www.pasc.org/interps/unofficial/db/p1003.2/pasc-1003.2-173.html
E9) Why does the pattern matching expression [A-Z]* match files beginning
with every letter except `z'?
Bash-2.03, Bash-2.05 and later versions honor the current locale setting
when processing ranges within pattern matching bracket expressions ([A-Z]).
This is what POSIX.2 and SUSv3/XPG6 specify.
The behavior of the matcher in bash-2.05 and later versions depends on the
current LC_COLLATE setting. Setting this variable to `C' or `POSIX' will
result in the traditional behavior ([A-Z] matches all uppercase ASCII
characters). Many other locales, including the en_US locale (the default
on many US versions of Linux) collate the upper and lower case letters like
this:
AaBb...Zz
which means that [A-Z] matches every letter except `z'. Others collate like
aAbBcC...zZ
which means that [A-Z] matches every letter except `a'.
The portable way to specify upper case letters is [:upper:] instead of
A-Z; lower case may be specified as [:lower:] instead of a-z.
Look at the manual pages for setlocale(3), strcoll(3), and, if it is
present, locale(1). If you have locale(1), you can use it to find
your current locale information even if you do not have any of the
LC_ variables set.
My advice is to put
export LC_COLLATE=C
into /etc/profile and inspect any shell scripts run from cron for
constructs like [A-Z]. This will prevent things like
rm [A-Z]*
from removing every file in the current directory except those beginning
with `z' and still allow individual users to change the collation order.
Users may put the above command into their own profiles as well, of course.
E10) Why does `cd //' leave $PWD as `//'?
POSIX.2, in its description of `cd', says that *three* or more leading
slashes may be replaced with a single slash when canonicalizing the
current working directory.
This is, I presume, for historical compatibility. Certain versions of
Unix, and early network file systems, used paths of the form
//hostname/path to access `path' on server `hostname'.
E11) If I resize my xterm while another program is running, why doesn't bash
notice the change?
This is another issue that deals with job control.
The kernel maintains a notion of a current terminal process group. Members
of this process group (processes whose process group ID is equal to the
current terminal process group ID) receive terminal-generated signals like
SIGWINCH. (For more details, see the JOB CONTROL section of the bash
man page.)
If a terminal is resized, the kernel sends SIGWINCH to each member of
the terminal's current process group (the `foreground' process group).
When bash is running with job control enabled, each pipeline (which may be
a single command) is run in its own process group, different from bash's
process group. This foreground process group receives the SIGWINCH; bash
does not. Bash has no way of knowing that the terminal has been resized.
There is a `checkwinsize' option, settable with the `shopt' builtin, that
will cause bash to check the window size and adjust its idea of the
terminal's dimensions each time a process stops or exits and returns control
of the terminal to bash. Enable it with `shopt -s checkwinsize'.
E12) Why don't negative offsets in substring expansion work like I expect?
When substring expansion of the form ${param:offset[:length} is used,
an `offset' that evaluates to a number less than zero counts back from
the end of the expanded value of $param.
When a negative `offset' begins with a minus sign, however, unexpected things
can happen. Consider
a=12345678
echo ${a:-4}
intending to print the last four characters of $a. The problem is that
${param:-word} already has a well-defined meaning: expand to word if the
expanded value of param is unset or null, and $param otherwise.
To use negative offsets that begin with a minus sign, separate the
minus sign and the colon with a space.
E13) Why does filename completion misbehave if a colon appears in the filename?
Filename completion (and word completion in general) may appear to behave
improperly if there is a colon in the word to be completed.
The colon is special to readline's word completion code: it is one of the
characters that breaks words for the completer. Readline uses these characters
in sort of the same way that bash uses $IFS: they break or separate the words
the completion code hands to the application-specific or default word
completion functions. The original intent was to make it easy to edit
colon-separated lists (such as $PATH in bash) in various applications using
readline for input.
This is complicated by the fact that some versions of the popular
`bash-completion' programmable completion package have problems with the
default completion behavior in the presence of colons.
The current set of completion word break characters is available in bash as
the value of the COMP_WORDBREAKS variable. Removing `:' from that value is
enough to make the colon not special to completion:
COMP_WORDBREAKS=${COMP_WORDBREAKS//:}
You can also quote the colon with a backslash to achieve the same result
temporarily.
E14) Why does quoting the pattern argument to the regular expression matching
conditional operator (=~) cause regexp matching to stop working?
In versions of bash prior to bash-3.2, the effect of quoting the regular
expression argument to the [[ command's =~ operator was not specified.
The practical effect was that double-quoting the pattern argument required
backslashes to quote special pattern characters, which interfered with the
backslash processing performed by double-quoted word expansion and was
inconsistent with how the == shell pattern matching operator treated
quoted characters.
In bash-3.2, the shell was changed to internally quote characters in single-
and double-quoted string arguments to the =~ operator, which suppresses the
special meaning of the characters special to regular expression processing
(`.', `[', `\', `(', `), `*', `+', `?', `{', `|', `^', and `$') and forces
them to be matched literally. This is consistent with how the `==' pattern
matching operator treats quoted portions of its pattern argument.
Since the treatment of quoted string arguments was changed, several issues
have arisen, chief among them the problem of white space in pattern arguments
and the differing treatment of quoted strings between bash-3.1 and bash-3.2.
Both problems may be solved by using a shell variable to hold the pattern.
Since word splitting is not performed when expanding shell variables in all
operands of the [[ command, this allows users to quote patterns as they wish
when assigning the variable, then expand the values to a single string that
may contain whitespace. The first problem may be solved by using backslashes
or any other quoting mechanism to escape the white space in the patterns.
Bash-4.0 introduces the concept of a `compatibility level', controlled by
several options to the `shopt' builtin. If the `compat31' option is enabled,
bash reverts to the bash-3.1 behavior with respect to quoting the rhs of
the =~ operator.
E15) Tell me more about the shell compatibility level.
Bash-4.0 introduced the concept of a `shell compatibility level', specified
as a set of options to the shopt builtin (compat31, compat32, compat40 at
this writing). There is only one current compatibility level -- each
option is mutually exclusive. This list does not mention behavior that is
standard for a particular version (e.g., setting compat32 means that quoting
the rhs of the regexp matching operator quotes special regexp characters in
the word, which is default behavior in bash-3.2 and above).
compat31 set
- the < and > operators to the [[ command do not consider the current
locale when comparing strings
- quoting the rhs of the regexp matching operator (=~) has no
special effect
compat32 set
- the < and > operators to the [[ command do not consider the current
locale when comparing strings
compat40 set
- the < and > operators to the [[ command do not consider the current
locale when comparing strings
- interrupting a command list such as "a ; b ; c" causes the execution
of the entire list to be aborted (in versions before bash-4.0,
interrupting one command in a list caused the next to be executed)
compat41 set
- interrupting a command list such as "a ; b ; c" causes the execution
of the entire list to be aborted (in versions before bash-4.1,
interrupting one command in a list caused the next to be executed)
- when in posix mode, single quotes in the `word' portion of a
double-quoted parameter expansion define a new quoting context and
are treated specially
compat42 set
- the replacement string in double-quoted pattern substitution is not
run through quote removal, as in previous versions
Section F: Things to watch out for on certain Unix versions
F1) Why can't I use command line editing in my `cmdtool'?
The problem is `cmdtool' and bash fighting over the input. When
scrolling is enabled in a cmdtool window, cmdtool puts the tty in
`raw mode' to permit command-line editing using the mouse for
applications that cannot do it themselves. As a result, bash and
cmdtool each try to read keyboard input immediately, with neither
getting enough of it to be useful.
This mode also causes cmdtool to not implement many of the
terminal functions and control sequences appearing in the
`sun-cmd' termcap entry. For a more complete explanation, see
that file examples/suncmd.termcap in the bash distribution.
`xterm' is a better choice, and gets along with bash much more
smoothly.
If you must use cmdtool, you can use the termcap description in
examples/suncmd.termcap. Set the TERMCAP variable to the terminal
description contained in that file, i.e.
TERMCAP='Mu|sun-cmd:am:bs:km:pt:li#34:co#80:cl=^L:ce=\E[K:cd=\E[J:rs=\E[s:'
Then export TERMCAP and start a new cmdtool window from that shell.
The bash command-line editing should behave better in the new
cmdtool. If this works, you can put the assignment to TERMCAP
in your bashrc file.
F2) I built bash on Solaris 2. Why do globbing expansions and filename
completion chop off the first few characters of each filename?
This is the consequence of building bash on SunOS 5 and linking
with the libraries in /usr/ucblib, but using the definitions
and structures from files in /usr/include.
The actual conflict is between the dirent structure in
/usr/include/dirent.h and the struct returned by the version of
`readdir' in libucb.a (a 4.3-BSD style `struct direct').
Make sure you've got /usr/ccs/bin ahead of /usr/ucb in your $PATH
when configuring and building bash. This will ensure that you
use /usr/ccs/bin/cc or acc instead of /usr/ucb/cc and that you
link with libc before libucb.
If you have installed the Sun C compiler, you may also need to
put /usr/ccs/bin and /opt/SUNWspro/bin into your $PATH before
/usr/ucb.
F3) Why does bash dump core after I interrupt username completion or
`~user' tilde expansion on a machine running NIS?
This is a famous and long-standing bug in the SunOS YP (sorry, NIS)
client library, which is part of libc.
The YP library code keeps static state -- a pointer into the data
returned from the server. When YP initializes itself (setpwent),
it looks at this pointer and calls free on it if it's non-null.
So far, so good.
If one of the YP functions is interrupted during getpwent (the
exact function is interpretwithsave()), and returns NULL, the
pointer is freed without being reset to NULL, and the function
returns. The next time getpwent is called, it sees that this
pointer is non-null, calls free, and the bash free() blows up
because it's being asked to free freed memory.
The traditional Unix mallocs allow memory to be freed multiple
times; that's probably why this has never been fixed. You can
run configure with the `--without-gnu-malloc' option to use
the C library malloc and avoid the problem.
F4) I'm running SVR4.2. Why is the line erased every time I type `@'?
The `@' character is the default `line kill' character in most
versions of System V, including SVR4.2. You can change this
character to whatever you want using `stty'. For example, to
change the line kill character to control-u, type
stty kill ^U
where the `^' and `U' can be two separate characters.
F5) Why does bash report syntax errors when my C News scripts use a
redirection before a subshell command?
The actual command in question is something like
< file ( command )
According to the grammar given in the POSIX.2 standard, this construct
is, in fact, a syntax error. Redirections may only precede `simple
commands'. A subshell construct such as the above is one of the shell's
`compound commands'. A redirection may only follow a compound command.
This affects the mechanical transformation of commands that use `cat'
to pipe a file into a command (a favorite Useless-Use-Of-Cat topic on
comp.unix.shell). While most commands of the form
cat file | command
can be converted to `< file command', shell control structures such as
loops and subshells require `command < file'.
The file CWRU/sh-redir-hack in the bash distribution is an
(unofficial) patch to parse.y that will modify the grammar to
support this construct. It will not apply with `patch'; you must
modify parse.y by hand. Note that if you apply this, you must
recompile with -DREDIRECTION_HACK. This introduces a large
number of reduce/reduce conflicts into the shell grammar.
F6) Why can't I use vi-mode editing on Red Hat Linux 6.1?
The short answer is that Red Hat screwed up.
The long answer is that they shipped an /etc/inputrc that only works
for emacs mode editing, and then screwed all the vi users by setting
INPUTRC to /etc/inputrc in /etc/profile.
The short fix is to do one of the following: remove or rename
/etc/inputrc, set INPUTRC=~/.inputrc in ~/.bashrc (or .bash_profile,
but make sure you export it if you do), remove the assignment to
INPUTRC from /etc/profile, add
set keymap emacs
to the beginning of /etc/inputrc, or bracket the key bindings in
/etc/inputrc with these lines
$if mode=emacs
[...]
$endif
F7) Why do bash-2.05a and bash-2.05b fail to compile `printf.def' on
HP/UX 11.x?
HP/UX's support for long double is imperfect at best.
GCC will support it without problems, but the HP C library functions
like strtold(3) and printf(3) don't actually work with long doubles.
HP implemented a `long_double' type as a 4-element array of 32-bit
ints, and that is what the library functions use. The ANSI C
`long double' type is a 128-bit floating point scalar.
The easiest fix, until HP fixes things up, is to edit the generated
config.h and #undef the HAVE_LONG_DOUBLE line. After doing that,
the compilation should complete successfully.
Section G: How can I get bash to do certain common things?
G1) How can I get bash to read and display eight-bit characters?
This is a process requiring several steps.
First, you must ensure that the `physical' data path is a full eight
bits. For xterms, for example, the `vt100' resources `eightBitInput'
and `eightBitOutput' should be set to `true'.
Once you have set up an eight-bit path, you must tell the kernel and
tty driver to leave the eighth bit of characters alone when processing
keyboard input. Use `stty' to do this:
stty cs8 -istrip -parenb
For old BSD-style systems, you can use
stty pass8
You may also need
stty even odd
Finally, you need to tell readline that you will be inputting and
displaying eight-bit characters. You use readline variables to do
this. These variables can be set in your .inputrc or using the bash
`bind' builtin. Here's an example using `bind':
bash$ bind 'set convert-meta off'
bash$ bind 'set meta-flag on'
bash$ bind 'set output-meta on'
The `set' commands between the single quotes may also be placed
in ~/.inputrc.
The script examples/scripts.noah/meta.bash encapsulates the bind
commands in a shell function.
G2) How do I write a function `x' to replace builtin command `x', but
still invoke the command from within the function?
This is why the `command' and `builtin' builtins exist. The
`command' builtin executes the command supplied as its first
argument, skipping over any function defined with that name. The
`builtin' builtin executes the builtin command given as its first
argument directly.
For example, to write a function to replace `cd' that writes the
hostname and current directory to an xterm title bar, use
something like the following:
cd()
{
builtin cd "$@" && xtitle "$HOST: $PWD"
}
This could also be written using `command' instead of `builtin';
the version above is marginally more efficient.
G3) How can I find the value of a shell variable whose name is the value
of another shell variable?
Versions of Bash newer than Bash-2.0 support this directly. You can use
${!var}
For example, the following sequence of commands will echo `z':
var1=var2
var2=z
echo ${!var1}
For sh compatibility, use the `eval' builtin. The important
thing to remember is that `eval' expands the arguments you give
it again, so you need to quote the parts of the arguments that
you want `eval' to act on.
For example, this expression prints the value of the last positional
parameter:
eval echo \"\$\{$#\}\"
The expansion of the quoted portions of this expression will be
deferred until `eval' runs, while the `$#' will be expanded
before `eval' is executed. In versions of bash later than bash-2.0,
echo ${!#}
does the same thing.
This is not the same thing as ksh93 `nameref' variables, though the syntax
is similar. Namerefs are available bash version 4.3, and work as in ksh93.
G4) How can I make the bash `time' reserved word print timing output that
looks like the output from my system's /usr/bin/time?
The bash command timing code looks for a variable `TIMEFORMAT' and
uses its value as a format string to decide how to display the
timing statistics.
The value of TIMEFORMAT is a string with `%' escapes expanded in a
fashion similar in spirit to printf(3). The manual page explains
the meanings of the escape sequences in the format string.
If TIMEFORMAT is not set, bash acts as if the following assignment had
been performed:
TIMEFORMAT=$'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS'
The POSIX.2 default time format (used by `time -p command') is
TIMEFORMAT=$'real %2R\nuser %2U\nsys %2S'
The BSD /usr/bin/time format can be emulated with:
TIMEFORMAT=$'\t%1R real\t%1U user\t%1S sys'
The System V /usr/bin/time format can be emulated with:
TIMEFORMAT=$'\nreal\t%1R\nuser\t%1U\nsys\t%1S'
The ksh format can be emulated with:
TIMEFORMAT=$'\nreal\t%2lR\nuser\t%2lU\nsys\t%2lS'
G5) How do I get the current directory into my prompt?
Bash provides a number of backslash-escape sequences which are expanded
when the prompt string (PS1 or PS2) is displayed. The full list is in
the manual page.
The \w expansion gives the full pathname of the current directory, with
a tilde (`~') substituted for the current value of $HOME. The \W
expansion gives the basename of the current directory. To put the full
pathname of the current directory into the path without any tilde
subsitution, use $PWD. Here are some examples:
PS1='\w$ ' # current directory with tilde
PS1='\W$ ' # basename of current directory
PS1='$PWD$ ' # full pathname of current directory
The single quotes are important in the final example to prevent $PWD from
being expanded when the assignment to PS1 is performed.
G6) How can I rename "*.foo" to "*.bar"?
Use the pattern removal functionality described in D3. The following `for'
loop will do the trick:
for f in *.foo; do
mv $f ${f%foo}bar
done
G7) How can I translate a filename from uppercase to lowercase?
The script examples/functions/lowercase, originally written by John DuBois,
will do the trick. The converse is left as an exercise.
G8) How can I write a filename expansion (globbing) pattern that will match
all files in the current directory except "." and ".."?
You must have set the `extglob' shell option using `shopt -s extglob' to use
this:
echo .!(.|) *
A solution that works without extended globbing is given in the Unix Shell
FAQ, posted periodically to comp.unix.shell. It's a variant of
echo .[!.]* ..?* *
(The ..?* catches files with names of three or more characters beginning
with `..')
Section H: Where do I go from here?
H1) How do I report bugs in bash, and where should I look for fixes and
advice?
Use the `bashbug' script to report bugs. It is built and
installed at the same time as bash. It provides a standard
template for reporting a problem and automatically includes
information about your configuration and build environment.
`bashbug' sends its reports to bug-bash@gnu.org, which
is a large mailing list gatewayed to the usenet newsgroup gnu.bash.bug.
Bug fixes, answers to questions, and announcements of new releases
are all posted to gnu.bash.bug. Discussions concerning bash features
and problems also take place there.
To reach the bash maintainers directly, send mail to
bash-maintainers@gnu.org.
H2) What kind of bash documentation is there?
First, look in the doc directory in the bash distribution. It should
contain at least the following files:
bash.1 an extensive, thorough Unix-style manual page
builtins.1 a manual page covering just bash builtin commands
bashref.texi a reference manual in GNU tex`info format
bashref.info an info version of the reference manual
FAQ this file
article.ms text of an article written for The Linux Journal
readline.3 a man page describing readline
Postscript, HTML, and ASCII files created from the above source are
available in the documentation distribution.
There is additional documentation available for anonymous FTP from host
ftp.cwru.edu in the `pub/bash' directory.
Cameron Newham and Bill Rosenblatt have written a book on bash, published
by O'Reilly and Associates. The book is based on Bill Rosenblatt's Korn
Shell book. The title is ``Learning the Bash Shell'', and the ISBN number
of the third edition, published in March, 2005, is 0-596-00965-8. Look for
it in fine bookstores near you. This edition of the book has been updated
to cover bash-3.0.
The GNU Bash Reference Manual has been published as a printed book by
Network Theory Ltd (Paperback, ISBN: 0-9541617-7-7, Nov. 2006). It covers
bash-3.2 and is available from most online bookstores (see
http://www.network-theory.co.uk/bash/manual/ for details). The publisher
will donate $1 to the Free Software Foundation for each copy sold.
Arnold Robbins and Nelson Beebe have written ``Classic Shell Scripting'',
published by O'Reilly. The first edition, with ISBN number 0-596-00595-4,
was published in May, 2005.
Chris F. A. Johnson, a frequent contributor to comp.unix.shell and
gnu.bash.bug, has written ``Shell Scripting Recipes: A Problem-Solution
Approach,'' a new book on shell scripting, concentrating on features of
the POSIX standard helpful to shell script writers. The first edition from
Apress, with ISBN number 1-59059-471-1, was published in May, 2005.
H3) What's coming in future versions?
These are features I hope to include in a future version of bash.
Rocky Bernstein's bash debugger (support is included with bash-4.0)
H4) What's on the bash `wish list' for future versions?
These are features that may or may not appear in a future version of bash.
breaking some of the shell functionality into embeddable libraries
a module system like zsh's, using dynamic loading like builtins
a bash programmer's guide with a chapter on creating loadable builtins
a better loadable interface to perl with access to the shell builtins and
variables (contributions gratefully accepted)
ksh93-like `xx.yy' variables (including some of the .sh.* variables) and
associated disipline functions
Some of the new ksh93 pattern matching operators, like backreferencing
H5) When will the next release appear?
The next version will appear sometime in 2015. Never make predictions.
This document is Copyright 1995-2014 by Chester Ramey.
Permission is hereby granted, without written agreement and
without license or royalty fees, to use, copy, and distribute
this document for any purpose, provided that the above copyright
notice appears in all copies of this document and that the
contents of this document remain unaltered.
0707010007eb32000081a40000000000000000000000015428b7350004cf2800000100000100b5ffffffffffffffff0000002600000000root/usr/local/share/doc/bash/CHANGES This document details the changes between this version, bash-4.3-release, and
the previous version, bash-4.3-rc2.
1. Changes to Bash
a. Only Posix-mode shells should exit on an assignment failure in the
temporary environment preceding a special builtin. This is how it's been
documented.
b. Fixed a bug that caused a failed special builtin to not exit a posix-mode
shell if the failing builtin was on the LHS of a && or ||.
c. Changed the handling of unquoted backslashes in regular expressions to be
closer to bash-4.2.
d. globstar (**) no longer traverses symbolic links that resolve to
directories. This eliminates some duplicate entries.
e. Fixed a bug that caused a SIGCHLD trap handler to not be able to change the
SIGCHLD disposition.
f. Fixed a bug that caused a crash when -x was enabled and a command
contained a printable multibyte (wide) character.
g. Fixed a bug that caused an interactive shell without line editing enabled
to read invalid data after receiving a SIGINT.
h. Fixed a bug that caused command word completion to fail if the directory in
$PATH where the completion would be found contained single or double quotes.
i. Fixed a bug that caused a shell with -v enabled to print commands in $()
multiple times.
2. Changes to Readline
a. Fixed a bug that caused `undo' to reference freed memory or null pointers.
3. New Features in Bash
a. The [[ -v ]] option now understands array references (foo[1]) and returns
success if the referenced element has a value.
------------------------------------------------------------------------------
This document details the changes between this version, bash-4.3-rc2, and the
previous version, bash-4.3-rc1.
1. Changes to Bash
a. Fixed a bug that left variables set by printf -v marked as invisible.
b. Fixed an off-by-one error in a job control warning message.
c. Fixed a bug that caused the shell to crash after declaring a nameref variable
without a value.
d. Fixed a bug that caused asynchronous commands to not set $? correctly.
e. Fixed a bug that caused out-of-order execution when executing aliases with
embedded newlines containing `.' commands.
f. Fixed a bug that caused error messages generated by expansion errors in
`for' commands to have the wrong line number.
g. Fixed a bug that caused the `wait' builtin to not be interruptible in an
interactive shell with job control enabled.
h. Fixed a bug that caused SIGINT and SIGQUIT to not be trappable in
asynchronous subshell commands.
i. Bash now requires that the value assigned to a nameref variable be a valid
shell identifier (variable name or array reference).
j. Converting an existing variable to a nameref variable now turns off the
-i/-l/-u/-c attributes.
k. Displaying a nameref variable with `declare -p' now displays the nameref
variable and its value rather than following the nameref chain.
l. Fixed a problem with interrupt handling that caused a second and subsequent
SIGINT to be ignored by interactive shells.
m. Fixed a bug that caused certain positional parameter and array expansions
to mishandle (discard) null positional parameters and array elements.
n. The shell no longer blocks receipt of signals while running trap handlers
for those signals, and allows most trap handlers to be run recursively
(running trap handlers while a trap handler is executing).
o. The shell now handles backslashes in regular expression arguments to the
[[ command's =~ operator slightly differently, resulting in more
consistent behavior.
2. Changes to Readline
a. Fixed a bug that could cause readline to crash and seg fault attempting to
expand an empty history entry.
b. Fixed a bug that caused a bad entry in the $LS_COLORS variable to abort all
color processing but leave color enabled.
c. Fixed a bug that caused display problems with multi-line prompts containing
invisible characters on multiple lines.
d. Fixed a bug that caused effects made by undoing changes to a history line to
be discarded.
3. New Features in Bash
4. New Features in Readline
a. When creating shared libraries on Mac OS X, the pathname written into the
library (install_name) no longer includes the minor version number.
------------------------------------------------------------------------------
This document details the changes between this version, bash-4.3-rc1, and the
previous version, bash-4.3-beta2.
1. Changes to Bash
a. Fixed a bug in bash completion that caused a tilde to be expanded even if
the `direxpand' option was not enabled.
b. Fixed a potential bug that could cause corrupted input in interactive shells
running without line editing and with `ignoreeof' enabled.
c. Fixed a bug that could cause failures when opening pipes back to shells
created to run process substitutions.
d. Fixed a bug that caused an assignment to TEXTDOMAIN to require TEXTDOMAINDIR
to be set in order to actually change the current text domain.
e. Changed the way redirections are printed to avoid confusion when the target
of an output redirection is a process substitution beginning with `>'.
2. Changes to Readline
a. Shared library building is now supported on Mac OS X 10.9 (Darwin 13).
3. New Features in Bash
a. `cd' has a new `-@' option to browse a file's extended attributes on
systems that support O_XATTR.
4. New Features in Readline
a. There are additional default key bindings for MinGW32
------------------------------------------------------------------------------
This document details the changes between this version, bash-4.3-beta2, and the
previous version, bash-4.3-beta.
1. Changes to Bash
a. Fixed a bug that caused assignment to an unset variable using a negative
subscript to result in a segmentation fault.
b. Fixed a bug that caused assignment to a string variable using a negative
subscript to use the incorrect index.
c. Fixed a bug that caused some strings to be interpreted as invalid
extended globbing expressions when used with the help builtin.
d. Fixed a bug that caused an attempt to trap a signal whose disposition
cannot be changed to reference uninitialized memory.
e. Command completion now skips assignment statements preceding a command
name and completes the command.
f. Fixed a bug that caused `compgen -f' in a non-interactive shell to dump
core under certain circumstances.
g. Fixed a bug that caused the `read -N' to misbehave when the input stream
contains 0xff.
2. Changes to Readline
a. Changed message when an incremental search fails to include "failed" in
the prompt and display the entire search string instead of just the last
matching portion.
b. Fixed a bug that caused an arrow key typed to an incremental search prompt
to process the key sequence incorrectly.
c. Additional key bindings for arrow keys on MinGW.
3. New Features in Bash
a. The help builtin now attempts substring matching (as it did through
bash-4.2) if exact string matching fails.
b. The fc builtin now interprets -0 as the current command line.
c. Completing directory names containing shell variables now adds a trailing
slash if the expanded result is a directory.
4. New Features in Readline
a. rl_change_environment: new application-settable variable that controls
whether or not Readline modifies the environment (currently readline
modifies only LINES and COLUMNS).
------------------------------------------------------------------------------
This document details the changes between this version, bash-4.3-beta, and the
previous version, bash-4.3-alpha.
1. Changes to Bash
a. Fixed a bug in the prompt directory name "trimming" code that caused
memory corruption and garbled the results.
b. Fixed a bug that caused single quotes that resulted from $'...' quoting
in the replacement portion of a double-quoted ${word/pat/rep} expansion
to be treated as quote characters.
c. Fixed a bug that caused assignment statements preceding a command word to
result in assignment statements following a declaration command to not be
expanded like assignment statements.
d. Fixed a bug with variable search order in the presence of local variables
with the same name as variables in the temporary environment supplied to
a shell function.
e. Fixed a bug that caused constructs like 1<(2) to be interpreted as process
substitutions even in an arithmetic context.
f. Fixed several cases where `invisible' variables (variables with attributes
but no values, which are technically unset) were treated incorrectly.
g. Fixed a bug that caused group commands in pipelines that were not the
last element to not run the EXIT trap.
h. Fixed a bug that caused `unset -n' to not unset a nameref variable in
certain cases.
i. Fixed the nameref circular reference checking to be less strict and only
disallow a nameref variable with the same value as its name at the global
scope.
j. Fixed a bug that caused trap handlers to be executed recursively,
corrupting internal data structures.
k. Fixed a bug that could result in bash not compiling if certain options were
not enabled.
l. Fixed a bug that caused the arithmetic expansion code to attempt variable
assignments when operator precedence prohibited them.
m. Word expansions like ${foo##bar} now understand indirect variable references.
n. Fixed a bug that caused `declare -fp name' to not display a function
definition.
o. Fixed a bug that caused asynchronous child processes to modify the stdin
file pointer when bash was using it to read a script, which modified the
parent's value as well.
2. Changes to Readline
a. Fixed a bug in vi mode that caused the arrow keys to set the saved last
vi-mode command to the wrong value.
b. Fixed a bug that caused double-quoted strings to be scanned incorrectly
when being used as the value of a readline variable assignment.
c. Fixed a bug with vi mode that prevented `.' from repeating a command
entered on a previous line (command).
d. Fixed a bug that could cause completion to core dump if it was interrupted
by a signal.
e. Readline now sends the meta-key enable string to the terminal if the
terminal has been successfully initialized.
f. Readline now calls the signal hook after resizing the terminal when it
receives a SIGWINCH.
g. Fixed a bug that could cause the history list code to perform an out-of-
bounds array reference if the history list is empty.
3. New Features in Bash
a. Shells started to run process substitutions now run any trap set on EXIT.
b. There is now a configure-time option to enable the globasciiranges option
by default.
c. The read builtin now checks its first variable argument for validity before
trying to read any input.
------------------------------------------------------------------------------
This document details the changes between this version, bash-4.3-alpha,
and the previous version, bash-4.2-release.
1. Changes to Bash
a. Fixed several bugs concerning incomplete bracket expressions in filename
generation (globbing) patterns.
b. Fixed a bug with single quotes and WORD in ${param op WORD} when running
in Posix mode.
c. Fixed a bug that caused the pattern removal and pattern substitution word
expansions and case statement word expansion to not match the empty string.
d. Fixed a bug that caused the tzset() function to not work after changing
the TZ enviroment variable.
e. Fixed a bug that caused the RHS of an assignment statement to undergo
word splitting when it contained an unquoted $@.
f. Fixed bugs that caused the shell to not react to a SIGINT sent while
waiting for a child process to exit.
g. Bash doesn't try to run things in a signal handler context when it gets a
signal (SIGINT/SIGHUP/etc) while reading input using readline but still
be responsive to terminating signals.
h. Fixed a bug that caused bash to go into an infinite loop if a filename
to be matched contained an invalid multibyte character.
i. Fixed a bug that caused PS4 to end up being truncated if it is longer
than 128 bytes.
j. Fixed a bug that caused brace expansion to not skip over double-quoted
command substitution.
k. System-specific updates for: DJGPP, HP/UX, Mac OS X
l. Fixed a bug in displaying commands that caused redirections to be associated
with the wrong part of the command.
m. Fixed the coproc cleanup to unset the appropriate shell variables when a
coproc terminates.
n. Fixed a bug that caused `fc' to dump core due to incorrect calculation of
the last history entry.
o. Added workarounds for FreeBSD's implementation of faccessat/eaccess and
`test -x'.
p. Fixed a bug that caused the shell to not match patterns containing
control-A.
q. Fixed a bug that could result in doubled error messages when the `printf'
builtin got a write error.
r. Fixed a bug that caused the shell to not correctly expand words containing
multiple consecutive quoted empty strings (""""""aa).
s. Fixed a bug that caused the shell to not correctly parse multi-line
process substitutions containing comments and quoted strings.
t. Fixed a problem with the bash malloc's internal idea of the top of the
memory heap that resulted in incorrect decisions to try to reduce the
break and give memory back to the kernel.
u. There are changes to the expansions peformed on compound array assignments,
in an effort to make foo=( [ind1]=bar [ind2]=baz ) identical to
foo[ind1]=bar foo[ind2]=baz.
v. Bash now reports an error if `read -a name' is used when `name' is an
existing associative array.
w. Fixed a bug that allowed an attempted assignment to a readonly variable
in an arithmetic expression to not return failure.
x. Fixed several bugs that caused completion functions to be invoked even when
the cursor was before the first word in the command.
y. Fixed a bug that caused parsing a command substitution to overwrite the
parsing state associated with the complete input line.
z. Fixed several bugs with the built-in snprintf replacement and field widths
and floating point.
aa. Fixed a bug that caused incorrect offset calculations and input buffer
corruption when reading files longer than 2^31 bytes.
bb. Fixed several bugs where bash performed arithmetic evaluation in contexts
where evaluation is suppressed.
cc. Fixed a bug that caused bash to close FIFOs used for process substitution
too early when a shell function was executing, but protect against using
all file descriptors when the shell functions are invoked inside loops.
dd. Added checks for printable (and non-printable) multibyte characters for
use in error messages.
ee. Fixed a bug that caused ^O (operate-and-get-next) to not work correctly
at the end of the history list.
ff. Fixed a bug that caused command-oriented history to incorrectly combine
here documents into one line.
gg. Fixed a bug that caused importing SHELLOPTS from the environment into a
Posix-mode shell to print an error message and refuse to parse it.
hh. Fixed a bug that caused the shell to delete an extra history entry when
using `history -s'.
ii. Fixed a bug that caused floating-point exceptions and overflow errors
for the / and % arithmetic operators when using INTMAX_MIN and -1.
jj. Fixed a bug that caused parsing errors when reading an arithmetic for
loop inside a command substitution.
kk. Fixed a bug that caused a readonly function to be unset when unset was
called without the -f or -v option.
ll. Fixed several bugs in the code that quotes characters special to regular
expressions when used in a quoted string on the RHS of the =~ operator
to the [[ command.
mm. Fixed a bug that caused redirections to fail because the file descriptor
limit was set to a value less than 10.
nn. Fixed a bug that caused the `read' builtin to execute code in a signal
handler context if read timed out.
oo. Fixed a bug that caused extended globbing patterns to not match files
beginning with `.' correctly when a `.' was explicitly supplied in the
pattern.
pp. Fixed a bug that caused key sequences longer than two characters to not
work when used with `bind -x'.
qq. Fixed a bug that resulted in redefined functions having the wrong source
file names in BASH_SOURCE.
rr. Fixed a bug that caused the read builtin to assign null strings to variables
when using `read -N', which caused core dumps when referenced
ss. Fixed a bug that caused `bash -m script' to not enable job control while
running the script.
tt. Fixed a bug that caused `printf -v var' to dump core when used with the
%b format code.
uu. Fixed a bug that caused the shell to exit with the wrong status if -e was
active and the shell exited on a substitution error.
vv. Fixed a bug that caused the shell to seg fault if an array variable with
the same name as an existing associative array was implicitly created by
an assignment (declare a[n]=b).
ww. Fixed a bug that caused a redirection to misbehave if the number specified
for a file descriptor overflows an intmax_t.
xx. Fixed several bugs with the handling of valid and invalid unicode character
values when used with the \u and \U escape sequences to printf and $'...'.
yy. Fixed a bug that caused tildes to not be escaped in expanded filenames,
making them subject to later expansion.
zz. When using the pattern substitution word expansion, bash now runs the
replacement string through quote removal, since it allows quotes in that
string to act as escape characters. This is not backwards compatible, so
it can be disabled by setting the bash compatibility mode to 4.2.
aaa. Fixed the rest of the cases where the shell runs non-allowed code in a
signal handler context.
bbb. Fixed a bug that caused spurious DEL characters (\177) to appear in
double-quoted expansion where the RHS is evaluated to the empty string.
ccc. Fixed a bug that caused the use of the shell's internal random number
generator for temporary file names to perturb the random number
sequence.
ddd. Fixed several bugs that caused `declare -g' to not set the right global
variables or to misbehave when declaring global indexed arrays.
eee. Fixed a logic bug that caused extended globbing in a multibyte locale to
cause failures when using the pattern substititution word expansions.
fff. Fixed a bug that caused the `lastpipe' option to corrupt the file
descriptor used to read the script.
ggg. Fixed a bug that causes the shell to delete DEL characters in the
expanded value of variables used in the same quoted string as variables
that expand to nothing.
hhh. Fixed a bug that caused the shell to assign the wrong value from an
assignment like (( x=7 )) when `x' was an existing array variable.
iii. Fixed a bug that caused the shell to misbehave when generating sequences
and the boundary values overflow an intmax_t.
jjj. Fixed a bug caused expansion errors if an expansion of "$@" appeared
next to another expansion (e.g.. "${@}${x}").
kkk. Fixed a potential buffer overflow bug when performing /dev/fd expansion.
lll. Fixed a bug that resulted in an extra semicolon being added to compound
assignments when they were added to the history list.
mmm. Fixed a bug that caused mapfile to read one extra line from the input.
nnn. Fixed a bug that caused the mail checking code to use uninitialized
values.
ooo. Fixed a bug that prevented history timestamps from being saved if the
history comment character is unset.
ppp. Fixed a bug that caused the case-modifying expansions to not work with
multibyte characters.
qqq. Fixed a bug that caused the edit-and-execute bindable readline command
to see the wrong data if invoked in the middle of a multi-line quoted
string.
rrr. Fixed a bug that resulted in the shell returning the wrong exit status
for a background command on systems that recycle PIDs very quickly.
sss. Fixed a bug that caused asynchronous group commands to not run any EXIT
trap defined in the body of the command.
ttt. Fixed a bug that caused `eval "... ; return"' to not clean up properly.
uuu. Fixed a bug that caused the shell to dump core if `read' reads an escaped
IFS whitespace character.
vvv. Fixed a bug that caused BASH_COMMAND to be set to an incorrect value when
executing a (...) subshell.
www. Fixed a couple of pointer aliasing bugs with the token string in arithmetic
evaluation.
xxx. Fixed a bug with parsing multi-line command substitutions when reading
the `do' keyword followed by whitespace.
yyy. Fixed a bug that caused the shell to seg fault if the time given to the
printf %(...)T format overflowed the value accepted by localtime(3).
zzz. Fixed a problem with displaying help topics in two columns when the
translated text contained multibyte characters.
aaaa. Fixed a bug with the extended globbing pattern matcher where a `*' was
followed by a negated extended glob pattern.
bbbb. Fixed a race condition with short-lived coproc creation and reaping that
caused the child process to be reaped before the various coproc shell
variables were initialized.
cccc. Fixed a bug where turning off `errexit' in command substitution subshells
was not reflected in $SHELLOPTS.
dddd. Partially fixed an inconsistency in how the shell treated shell
functions run from an EXIT trap.
eeee. Fixed a bug in how the shell invalidated FIFOs used for process
substitution when executing a pipeline (once rather than in every child).
ffff. Fixed a bug that occurred when expanding a special variable ($@, $*)
within double quotes and the expansion resulted in an empty string.
gggg. Fixed bugs with executing a SIGCHLD trap handler to make sure that it's
executed once per exited child.
hhhh. Fixed a bug that caused `declare' and `test' to find variables that
had been given attributes but not assigned values. Such variables are
not set.
iiii. Fixed a bug that caused commands in process substitutions to not look in
the local temporary environment when performing word expansions.
jjjj. Fixed several problems with globstar expansions (**/**) returning null
filenames and multiple instances of the same pathname.
kkkk. Fixed an oversight that did not allow the exit status of `coproc' to
be inverted using `!'.
llll. Fixed a bug that caused the -e option to be re-enabled using `set -e'
even when executing in a context where -e is ignored.
mmmm. Fixed a (mostly theoretical) bug with input lines longer than SIZE_MAX.
nnnn. Fixed a bug that could result in double evaluation of command
substitutions when they appear in failed redirections.
oooo. Fixed a bug that could cause seg faults during `mapfile' callbacks if
the callback unsets the array variable mapfile is using.
pppp. Fixed several problems with variable assignments using ${var:=value}
when the variable assignment is supposed to have side effects.
qqqq. Fixed a bug that caused a failure of an assignment statement preceding a
builtin caused the next invocation of a special builtin to exit the shell.
rrrr. Fixed several problems with IFS when it appears in the temporary environment
and is used in redirections.
ssss. Fixed a problem that caused IFS changes using ${IFS:=value} to modify
how preceding expansions were split.
tttt. Fixed a problem that caused subshells to not run an EXIT trap they set.
uuuu. Fixed a problem that caused shells started in posix mode to attempt to
import shell functions with invalid names from the environment. We now
print a warning.
vvvv. Worked around a kernel problem that caused SIGCHLD to interrupt open(2)
on a FIFO used for process substitution, even if the SIGCHLD handler was
installed with the SA_RESTART flag.
wwww. Fixed a problem that resulted in inconsistent expansion of $* and ${a[*]}.
xxxx. Fixed a problem that caused `read -t' to crash when interrupted by
SIGINT.
yyyy. Fixed a problem that caused pattern removal to fail randomly because the
pattern matcher read beyond the end of a string.
zzzz. Fixed a bug that caused core dumps when shell functions tried to create
local shadow copies of special variables like GROUPS.
aaaaa. Fixed a bug that caused SIGTERM to be occasionally lost by children of
interactive shells when it arrived before the child process reset the
handler from SIG_DFL.
bbbbb. Fixed a bug that caused redirections like <&n- to leave file descriptor
n closed if executed with a builtin command.
ccccc. Fixed a bug that caused incorrect completion quoting when completing a
word containing a globbing character with `show-all-if-ambiguous' set.
ddddd. Fixed a bug that caused printf's %q format specifier not to quote a
tilde even if it appeared in a location where it would be subject to
tilde expansion.
2. Changes to Readline
a. Fixed a bug that did not allow the `dd', `cc', or `yy' vi editing mode
commands to work on the entire line.
b. Fixed a bug that caused redisplay problems with prompts longer than 128
characters and history searches.
c. Fixed a bug that caused readline to try and run code to modify its idea
of the screen size in a signal handler context upon receiving a SIGWINCH.
d. Fixed a bug that caused the `meta' key to be enabled beyond the duration
of an individual call top readline().
e. Added a workaround for a wcwidth bug in Mac OS X that caused readline's
redisplay to mishandle zero-width combining characters.
f. Fixed a bug that caused readline to `forget' part of a key sequence when
a multiple-key sequence caused it to break out of an incremental search.
g. Fixed bugs that caused readline to execute code in a signal handler
context if interrupted while reading from the file system during completion.
h. Fixed a bug that caused readline to `forget' part of a key sequence when
reading an unbound multi-character key sequence.
i. Fixed a bug that caused Readline's signal handlers to be installed beyond
the bounds of a single call to readline().
j. Fixed a bug that caused the `.' command to not redo the most recent `R'
command in vi mode.
k. Fixed a bug that caused ignoring case in completion matches to result in
readline using the wrong match.
l. Paren matching now works in vi insert mode.
m. Fix menu-completion to make show-all-if-ambiguous and menu-complete-display-prefix
work together.
n. Fixed a bug that didn't allow the `cc', `dd', or `yy' commands to be redone
in vi editing mode.
o. Fixed a bug that caused the filename comparison code to not compare
multibyte characters correctly when using case-sensitive or case-mapping
comparisons.
p. Fixed the input reading loop to call the input hook function only when there
is no terminal input available.
q. Fixed a bug that caused binding a macro to a multi-character key sequence
where the sequence and macro value share a common prefix to not perform
the macro replacement.
r. Fixed several redisplay errors with multibyte characters and prompts
containing invisible characters when using horizontal scrolling.
s. Fixed a bug that caused redisplay errors when trying to overwrite
existing characters using multibyte characters.
3. New Features in Bash
a. The `helptopic' completion action now maps to all the help topics, not just
the shell builtins.
b. The `help' builtin no longer does prefix substring matching, so `help read'
does not match `readonly'.
c. The shell can be compiled to not display a message about processes that
terminate due to SIGTERM.
d. Non-interactive shells now react to the setting of checkwinsize and set
LINES and COLUMNS after a foreground job exits.
e. There is a new shell option, `globasciiranges', which, when set to on,
forces globbing range comparisons to use character ordering as if they
were run in the C locale.
f. There is a new shell option, `direxpand', which makes filename completion
expand variables in directory names in the way bash-4.1 did.
g. In Posix mode, the `command' builtin does not change whether or not a
builtin it shadows is treated as an assignment builtin.
h. The `return' and `exit' builtins accept negative exit status arguments.
i. The word completion code checks whether or not a filename containing a
shell variable expands to a directory name and appends `/' to the word
as appropriate. The same code expands shell variables in command names
when performing command completion.
j. In Posix mode, it is now an error to attempt to define a shell function
with the same name as a Posix special builtin.
k. When compiled for strict Posix conformance, history expansion is disabled
by default.
l. The history expansion character (!) does not cause history expansion when
followed by the closing quote in a double-quoted string.
m. `complete' and its siblings compgen/compopt now takes a new `-o noquote'
option to inhibit quoting of the completions.
n. Setting HISTSIZE to a value less than zero causes the history list to be
unlimited (setting it 0 zero disables the history list).
o. Setting HISTFILESIZE to a value less than zero causes the history file size
to be unlimited (setting it to 0 causes the history file to be truncated
to zero size).
p. The `read' builtin now skips NUL bytes in the input.
q. There is a new `bind -X' option to print all key sequences bound to Unix
commands.
r. When in Posix mode, `read' is interruptible by a trapped signal. After
running the trap handler, read returns 128+signal and throws away any
partially-read input.
s. The command completion code skips whitespace and assignment statements
before looking for the command name word to be completed.
t. The build process has a new mechanism for constructing separate help files
that better reflects the current set of compilation options.
u. The -nt and -ot options to test now work with files with nanosecond
timestamp resolution.
v. The shell saves the command history in any shell for which history is
enabled and HISTFILE is set, not just interactive shells.
w. The shell has `nameref' variables and new -n(/+n) options to declare and
unset to use them, and a `test -R' option to test for them.
x. The shell now allows assigning, referencing, and unsetting elements of
indexed arrays using negative subscripts (a[-1]=2, echo ${a[-1]}) which
count back from the last element of the array.
y. The {x} operators to [[ do string comparisons using the current locale
only if the compatibility level is greater than 40 (set to 41 by default).
4. New Features in Readline
------------------------------------------------------------------------------
This document details the changes between this version, bash-4.1-alpha,
and the previous version, bash-4.0-release.
1. Changes to Bash
a. Fixed bugs in the parser involving new parsing of the commands contained
in command substitution when the substitution is read.
b. Fixed a bug that caused the shell to dump core when performing programmable
completion using a shell function.
c. Fixed a bug in `mapfile' that caused it to invoke callbacks at the wrong
time.
d. Fixed a bug that caused the shell to dump core when listing jobs in the
`exit' builtin.
e. Fixed several bugs encountered when reading subscripts in associative
array assignments and expansions.
f. Fixed a bug that under some circumstances caused an associative array to
be converted to an indexed array.
g. Fixed a bug that caused syntax errors and SIGINT interrupts to not set
$? to a value > 128.
h. Fixed a bug that caused the shell to remove FIFOs associated with process
substitution inside shell functions.
i. Fixed a bug that caused terminal attributes to not be reset when the
`read' builtin timed out.
j. Fixed a bug in brace expansion that caused unwanted zero padding of the
expanded terms.
k. Fixed a bug that prevented the |& construct from working as intended when
used with a simple command with additional redirections.
l. Fixed a bug with the case statment ;& terminator that caused the shell to
dereference a NULL pointer.
m. Fixed a bug that caused assignment statements or redirections preceding
a simple command name to inhibit alias expansion.
n. Fixed the behavior of `set -u' to conform to the latest Posix interpretation:
every expansion of an unset variable except $@ and $* will cause the
shell to exit.
o. Fixed a bug that caused double-quoted expansions of $* inside word
expansions like ${x#$*} to not expand properly when $IFS is empty.
p. Fixed a bug that caused traps to set $LINENO to the wrong value when they
execute.
q. Fixed a bug that caused off-by-one errors when computing history lines in
the `fc' builtin.
r. Fixed a bug that caused some terminating signals to not exit the shell
quickly enough, forcing the kernel to send the signal (e.g., SIGSEGV)
multiple times.
s. Fixed a bug that caused the shell to attempt to add empty lines to the
history list when reading here documents.
t. Made some internal changes that dramatically speeds up sequential indexed
array access.
u. Fixed a bug that caused the shell to write past the end of a string when
completing a double-quoted string ending in a backslash.
v. Fixed a bug that caused the shell to replace too many characters when a
pattern match was null in a ${foo//bar} expansion.
w. Fixed bugs in the expansion of ** that caused duplicate directory names
and the contents of the current directory to be omitted.
x. Fixed a bug that caused $? to not be set correctly when referencing an
unset variable with set -u and set -e enabled.
y. Fixed a bug caused by executing an external program from the DEBUG trap
while a pipeline was running. The effect was to disturb the pipeline
state, occasionally causing it to hang.
z. Fixed a bug that caused the ** glob expansion to dump core if it
encountered an unsearchable directory.
aa. Fixed a bug that caused `command -v' and `command -V' to not honor the
path set by the -p option.
bb. Fixed a bug that caused brace expansion to take place too soon in some
compound array assignments.
cc. Fixed a bug that caused programmable completion functions' changes to
READLINE_POINT to not be reflected back to readline.
dd. Fixed a bug that caused the shell to dump core if a trap was executed
during a shell assignment statement.
ee. Fixed an off-by-one error when computing the number of positional
parameters for the ${@:0:n} expansion.
ff. Fixed a problem with setting COMP_CWORD for programmable completion
functions that could leave it set to -1.
gg. Fixed a bug that caused the ERR trap to be triggered in some cases where
`set -e' would not have caused the shell to exit.
hh. Fixed a bug that caused changes made by `compopt' to not persist past the
completion function in which compopt was executed.
ii. Fixed a bug that caused the list of hostname completions to not be cleared
when HOSTNAME was unset.
jj. Fixed a bug that caused variable expansion in here documents to look in
any temporary environment.
kk. Bash and readline can now convert file names between precomposed and
decomposed Unicode on Mac OS X ("keyboard" and file system forms,
respectively). This affects filename completion (using new
rl_filename_rewrite_hook), globbing, and readline redisplay.
ll. The ERR and EXIT traps now see a non-zero value for $? when a parser
error after set -e has been enabled causes the shell to exit.
mm. Fixed a bug that in brace expansion that caused zero-prefixed terms to
not contain the correct number of digits.
nn. Fixed a bug that caused the shell to free non-allocated memory when
unsetting an associative array which had had a value implicitly assigned
to index "0".
oo. Fixed a memory leak in the ${!prefix@} expansion.
pp. Fixed a bug that caused printf to not correctly report all write errors.
qq. Fixed a bug that caused single and double quotes to act as delimiters
when splitting a command line into words for programmable completion.
rr. Fixed a bug that caused ** globbing that caused **/path/* to match every
directory, not just those matching `path'.
ss. Fixed a bug that caused the shell to dump core when running `help' without
arguments if the terminal width was fewer than 7 characters.
2. Changes to Readline
a. The SIGWINCH signal handler now avoids calling the redisplay code if
one arrives while in the middle of redisplay.
b. Changes to the timeout code to make sure that timeout values greater
than one second are handled better.
c. Fixed a bug in the redisplay code that was triggered by a prompt
containing invisible characters exactly the width of the screen.
d. Fixed a bug in the redisplay code encountered when running in horizontal
scroll mode.
e. Fixed a bug that prevented menu completion from properly completing
filenames.
f. Fixed a redisplay bug caused by a multibyte character causing a line to
wrap.
g. Fixed a bug that caused key sequences of two characters to not be
recognized when a longer sequence identical in the first two characters
was bound.
h. Fixed a bug that caused history expansion to be attempted on $'...'
single-quoted strings.
i. Fixed a bug that caused incorrect redisplay when the prompt contained
multibyte characters in an `invisible' sequence bracketed by \[ and
\].
j. Fixed a bug that caused history expansion to short-circuit after
encountering a multibyte character.
3. New Features in Bash
a. Here-documents within $(...) command substitutions may once more be
delimited by the closing right paren, instead of requiring a newline.
b. Bash's file status checks (executable, readable, etc.) now take file
system ACLs into account on file systems that support them.
c. Bash now passes environment variables with names that are not valid
shell variable names through into the environment passed to child
processes.
d. The `execute-unix-command' readline function now attempts to clear and
reuse the current line rather than move to a new one after the command
executes.
e. `printf -v' can now assign values to array indices.
f. New `complete -E' and `compopt -E' options that work on the "empty"
completion: completion attempted on an empty command line.
g. New complete/compgen/compopt -D option to define a `default' completion:
a completion to be invoked on command for which no completion has been
defined. If this function returns 124, programmable completion is
attempted again, allowing a user to dynamically build a set of completions
as completion is attempted by having the default completion function
install individual completion functions each time it is invoked.
h. When displaying associative arrays, subscripts are now quoted.
i. Changes to dabbrev-expand to make it more `emacs-like': no space appended
after matches, completions are not sorted, and most recent history entries
are presented first.
j. The [[ and (( commands are now subject to the setting of `set -e' and the
ERR trap.
k. The source/. builtin now removes NUL bytes from the file before attempting
to parse commands.
l. There is a new configuration option (in config-top.h) that forces bash to
forward all history entries to syslog.
m. A new variable $BASHOPTS to export shell options settable using `shopt' to
child processes.
n. There is a new confgure option that forces the extglob option to be
enabled by default.
o. New variable $BASH_XTRACEFD; when set to an integer bash will write xtrace
output to that file descriptor.
p. If the optional left-hand-side of a redirection is of the form {var}, the
shell assigns the file descriptor used to $var or uses $var as the file
descriptor to move or close, depending on the redirection operator.
q. The < and > operators to the [[ conditional command now do string
comparison according to the current locale.
r. Programmable completion now uses the completion for `b' instead of `a'
when completion is attempted on a line like: a $(b c.
s. Force extglob on temporarily when parsing the pattern argument to
the == and != operators to the [[ command, for compatibility.
t. Changed the behavior of interrupting the wait builtin when a SIGCHLD is
received and a trap on SIGCHLD is set to be Posix-mode only.
u. The read builtin has a new `-N nchars' option, which reads exactly NCHARS
characters, ignoring delimiters like newline.
4. New Features in Readline
a. New bindable function: menu-complete-backward.
b. In the vi insertion keymap, C-n is now bound to menu-complete by default,
and C-p to menu-complete-backward.
c. When in vi command mode, repeatedly hitting ESC now does nothing, even
when ESC introduces a bound key sequence. This is closer to how
historical vi behaves.
d. New bindable function: skip-csi-sequence. Can be used as a default to
consume key sequences generated by keys like Home and End without having
to bind all keys.
e. New application-settable function: rl_filename_rewrite_hook. Can be used
to rewite or modify filenames read from the file system before they are
compared to the word to be completed.
f. New bindable variable: skip-completed-text, active when completing in the
middle of a word. If enabled, it means that characters in the completion
that match characters in the remainder of the word are "skipped" rather
than inserted into the line.
g. The pre-readline-6.0 version of menu completion is available as
"old-menu-complete" for users who do not like the readline-6.0 version.
h. New bindable variable: echo-control-characters. If enabled, and the
tty ECHOCTL bit is set, controls the echoing of characters corresponding
to keyboard-generated signals.
i. New bindable variable: enable-meta-key. Controls whether or not readline
sends the smm/rmm sequences if the terminal indicates it has a meta key
that enables eight-bit characters.
------------------------------------------------------------------------------
This document details the changes between this version, bash-4.0-release,
and the previous version, bash-4.0-rc1.
1. Changes to Bash
a. Changed the message printed when setlocale(3) fails to only include the
strerror error text if the call changes errno.
b. Changed trap command execution to reset the line number before running a
trap (except DEBUG and RETURN traps).
c. Fixed behavior of case-modifiying word expansions to not work on
individual words within a variable's value.
d. Fixed a bug that caused mapfile to not be interruptible when run in an
interactive shell.
e. Fixed a bug that caused mapfile to not run callbacks for the first line
read.
f. Fixed a bug that caused mapfile to not honor EOF typed in an interactive
shell.
g. Fixed the coprocess reaping code to not run straight from a signal handler.
h. Fixed a bug that caused printf -b to ignore the first % conversion specifier
in the format string on 64-bit systems.
i. Fixed a bug that caused incorrect word splitting when `:', `=', or `~'
appeared in $IFS.
j. Fixed a bug that caused data corruption in the programmable completion code
when a shell function called from a completion aborted execution.
k. Fixed a bug that caused the CPU usage reported by the `time' builtin to be
capped at 100%.
l. Changed behavior of shell when -e option is in effect to reflect consensus
of Posix shell standardization working group.
m. Fixed a bug introduced in bash-4.0-alpha that caused redirections to not
be displayed by `type' or `declare' when appearing in functions under
certain circumstances.
2. Changes to Readline
a. Fixed a bug that caused !(...) extended glob patterns to inhibit later
history expansion.
b. Reworked the signal handling to avoid calling disallowed functions from a
signal handler.
3. New Features in Bash
a. `readarray' is now a synonym for `mapfile'.
------------------------------------------------------------------------------
This document details the changes between this version, bash-4.0-rc1,
and the previous version, bash-4.0-beta2.
1. Changes to Bash
a. Fixed a bug that caused parsing errors when a $()-style command
substitution was follwed immediately by a quoted newline.
b. Fixed a bug that caused extended shell globbing patterns beginning with
`*(' to not work when used with pattern substitution word expansions.
------------------------------------------------------------------------------
This document details the changes between this version, bash-4.0-beta2,
and the previous version, bash-4.0-beta.
1. Changes to Bash
a. Fixed a bug that caused failed word expansions to set $? but not
PIPESTATUS.
b. Changed filename completion to quote the tilde in a filename with a
leading tilde that exists in the current directory.
c. Fixed a bug that caused a file descriptor leak when performing
redirections attached to a compound command.
d. Fixed a bug that caused expansions of $@ and $* to not exit the shell if
the -u option was enabled and there were no posititional parameters.
e. Fixed a bug that resulted in bash not terminating immediately if a
terminating signal was received while performing output.
f. Fixed a bug that caused the shell to crash after creating 256 process
substitutions during word completion.
2. Changes to Readline
a. Fixed a bug that caused redisplay errors when using prompts with invisible
characters and numeric arguments to a command in a multibyte locale.
b. Fixed a bug that caused redisplay errors when using prompts with invisible
characters spanning more than two physical screen lines.
------------------------------------------------------------------------------
This document details the changes between this version, bash-4.0-beta,
and the previous version, bash-4.0-alpha.
1. Changes to Bash
a. Fixed a typo that caused a variable to be used before initialization
while parsing Posix-style command substitutions.
b. Fixed a bug that caused stray ^? when the expansion of a parameter used
as part of a pattern removal expansion is empty, but part of a non-
empty string.
c. Fixed a bug that could cause strings not converted to numbers by strtol
to be treated as if the conversion had been successful.
d. The `return' builtin now accepts no options and requires a `--' before
a negative return value, as Posix requires.
e. Fixed a bug that caused local variables to be created with the empty
string for a value rather than no value.
f. Changed behavior so the shell now acts as if it received an interrupt
when a pipeline is killed by SIGINT while executing a list.
g. Fixed a bug that caused `declare var' and `typeset var' to initialize
`var' to the empty string.
h. Changed `bind' builtin to print a warning but proceed if invoked when
line editing is not active.
i. Fixed a bug that caused the shell to exit when the `errexit' option is
set and a command in a pipeline returns a non-zero exit status.
j. Fixed a bug that caused the shell to not run the exit trap in a command
run with `bash -c' under some circumstances.
k. Fixed a bug that caused parser errors to occasionally not set $? when
running commands with `eval'.
l. Fixed a bug that caused stray control characters when evaluating compound
array assignments containing $'\x7f' escapes.
m. Fixed a bug that caused redirections involving file descriptor 10 as the
target to behave incorrectly.
n. Fixed a bug that could cause memory to be freed multiple times when
assigning to COMP_WORDBREAKS.
o. Fixed a bug that could cause NULL pointer dereferences when COMP_WORDBREAKS
was unset.
2. Changes to Readline
3. New Features in Bash
a. A value of 0 for the -t option to `read' now returns success if there is
input available to be read from the specified file descriptor.
b. CDPATH and GLOBIGNORE are ignored when the shell is running in privileged
mode.
c. New bindable readline functions shell-forward-word and shell-backward-word,
which move forward and backward words delimited by shell metacharacters
and honor shell quoting.
d. New bindable readline functions shell-backward-kill-word and shell-kill-word
which kill words backward and forward, but use the same word boundaries
as shell-forward-word and shell-backward-word.
4. New Features in Readline
a. If the kernel supports it, readline displays special characters
corresponding to a keyboard-generated signal when the signal is received.
------------------------------------------------------------------------------
This document details the changes between this version, bash-4.0-alpha,
and the previous version, bash-3.2-release.
1. Changes to Bash
a. Fixed several bugs in old-style `` command substitution parsing, including
comment parsing and quoted string handling.
b. Fixed problems parsing arguments to the [[ command's =~ regular expression
matching operator: metacharacter and whitespace parsing.
c. Fixed a bug that caused the shell to inappropriately reuse high-numbered
file descriptors it used internally.
d. Fixed a bug in pattern replacement word expansions that caused a `/' as
the first character of an expanded pattern to be mistaken for a global
replacement specifier.
e. Fixed several problems with the asprintf and snprintf replacement functions
that caused hangs and crashes.
f. Fixed a bug in the calculation of the current and previous job that caused
it to refer to incorrect jobs.
g. Fixed a bug in the check for the validity of a hashed command pathname that
caused unnecessary hash table deletions and additions.
h. Fixed a bug that caused child processes to inherit the wrong value for $!.
i. Fixed a bug that caused `.' to fail to read and execute commands from non-
regular files such as devices or named pipes.
j. Fixed a bug in printf formatting for the %x and %X expansions that occurred
on some systems.
k. Fixed a bug that caused the shell to crash when creating temporary files if
$TMPDIR named a non-writable directory.
l. Fixed a bug that caused the shell to ignore $TMPDIR when creating temporary
files under some circumstances.
m. Fixed a bug that caused named pipes created by process substitution to not
be cleaned up.
n. Fixed a bug that caused HISTTIMEFORMAT to not be honored when it appeared
in the initial shell environment.
o. Fixed several bugs in the expansion of $* and $@ (quoted and unquoted)
when IFS is null or contains non-whitespace characters; the same changes
apply to arrays subscripted with * or @.
p. Fixed several problems with pattern substitution expansions on the
positional parameters and arrays subscripted with * or @ that occurred
when $IFS was set to the empty string.
q. Made a change to the default locale initialization code that should
result in better behavior from the locale-aware library functions.
r. Fixed a bug that caused compacting the jobs list to drop jobs.
s. Fixed a bug that caused jumps back to the top-level processing loop from
a builtin command to leave the shell in an inconsistent state.
t. Fixed a bug that caused characters that would be escaped internally to be
doubled when escaped with a backslash.
u. Fixed the initialization of mailboxes to not cause maildirs to be read
(and stat(2) called for every message file) at shell startup.
v. Fixed a bug that caused the shell to not display $PS2 when the read builtin
reads a line continued with a backslash.
w. Fixed a bug that caused errors in word splitting when $IFS contained
characters used for internal quoting.
x. Fixed bugs that caused problems with output from shell builtins not being
completely displayed on some systems.
y. Fixed a bug that caused output to be lost when a redirection is acting on
the shell's output file descriptor.
z. Fixed bugs caused by shell builtins not checking for all write errors.
aa. Fixed a problem that caused the shell to dump core if expansions on the
pattern passed to the pattern removal word expansions resulted in expansion
errors.
bb. Fixed a bug that caused bash to loop infinitely after creating and
waiting for 4096 jobs.
cc. Fixed a bug that caused bash to lose the status of a background job under
certain circumstances.
dd. Fixed a bug that caused bash to not look in the temporary environment
when performing variable lookup under certain circumstances.
ee. Fixed a bug that caused bash to close file descriptors greater than 10
when they were used in redirections.
ff. Fixed a problem that caused the shell to attempt to read from the standard
input when called as `bash -i script'.
gg. Fixed a memory leak and variable initialization problems when the -v option
was supplied to `printf' that could cause incorrect results.
hh. Fixed a bug that caused the `read' builtin to count bytes when the -n option
was supplied, rather than (possibly multibyte) characters.
ii. Fixed a bug when displaying a function due to not converting the function
to an external form.
jj. Changed job control initialization to ensure that the shell has a tty
as its controlling terminal before enabling job control.
kk. Fixed a bug with the `test' builtin that caused it to misinterpret
arguments beginning with `-' but containing more than one character.
ll. Fixed bug that could cause the shell to dump core in certain cases where
a command sets the SIGINT disposition to the default.
mm. Fixed a bug in the pattern replacement (affecting both word expansion
and the `fc' builtin) that occurred when the pattern and replacement
strings were empty.
nn. Fixed a bug that caused an arithmetic evaluation error to disable all
further evaluation.
oo. Fixed a bug in pathname expansion that caused it to interpret backslashes
in the pathname as quoting characters.
pp. Fixed a bug in the replacement getcwd() implementation that could cause
memory to be overwritten.
qq. When in Posix mode, the `ulimit' builtin now uses a block size of 512 for
the `-c' and `-f' options.
rr. Brace expansion now allows process substitutions to pass through unchanged.
ss. Fixed a problem in the command name completion code to avoid quoting
escaped special characters twice when the command name begins with a tilde.
tt. Fixed a problem in the printf builtin that resulted in single-byte
output for the "'" escape, even when using multibyte characters.
uu. Fixed a bug that caused the failure exit status to be lost when redirections
attached to a compound command failed.
vv. Fixed a bug that caused the internal random number generator to not be
re-seeded correctly when creating a subshell.
ww. Fixed a bug that could cause the bash replacement getcwd to overwrite
memory.
xx. Fixed a bug that caused the shell to not receive SIGINT if it was sent
while the shell was waiting for a command substitution to terminate, and
make sure the exit status is correct when it does.
yy. Fixed a bug that resulted in the second and subsequent children spawned
by a shell begun to run a command substitution being placed into the
wrong process group.
zz. Fixed a bug that caused the results of successful tilde expansion to be
subject to pathname expansion and word splitting.
aaa. Fixed a bug that could cause the shell to hang if it encountered an
error that caused it to jump back to the top processing loop during a
command substitution or `eval' command.
bbb. Fixed a bug that caused the `read' builtin to use the tty's attributes
instead of those of the file descriptor passed with the -u option when
processing the -n and -d options.
ccc. Fixed a bug that caused incorrect expansion of ${array[@]:foo} if the
first character of $IFS was not whitespace.
ddd. Fixed a bug that occurred when scanning for the ending delimiter of a
${parameter/pat/sub} expansion.
eee. Fixed a bug that caused the shell to inappropriately expand command
substitutions in words when expanding directory names for completion.
fff. Fixed a bug that caused the `fc' builtin to look too far back in the
history list under certain circumstances.
ggg. Fixed a bug that caused a shell running in Posix mode to search $PWD for
a file specified as an argument to source/. when the file was not found
in $PATH.
hhh. Fixed a bug that caused the shell to modify the case of a command word
found via command completion when the shell was performing case-
insensitive completion.
iii. Fixed a bug that caused the shell to search $PATH for an argument to
source/. even when it contained a `/'.
jjj. Fixed a bug that caused brace expansion to misorder expansions when the
locale did not have a collating order like aAbBcC...zZ.
kkk. Fixed a bug that did not allow `set +o history' to have any effect when
run in a startup file or from a sourced file.
lll. Fixed a bug with the precedence of the ?: conditional arithmetic operator.
mmm. Fixed a bug that caused side effects of temporary variable assignments
to persist in the shell environment.
nnn. Fixed a bug that caused the terminal to be left in non-canonical mode
when using editing commands that invoke the an editor on the current
command line.
ooo. Fixed a bug that caused globbing characters and characters in $IFS to not
be quoted appropriately when displaying assignment statements.
ppp. Fixed a bug that caused the `-e' option to be inherited when sourcing a
file or evaluating a command with `eval' even if the return value of the
command was supposed to be ignored.
qqq. Fixed a bug that caused the shell to attempt to created variables with
invalid names if such names appeared in the initial environment.
rrr. Fixed a bug with quote removal in strings where the final character is a
backslash.
sss. Fixed a bug that caused the effects of special variables to persist even
when the variables were unset as part of the shell reinitializing itself
to execute a shell script.
ttt. Fixed a bug that caused the history to not be saved after `history -c' or
`history -d' was executed until a sufficient number of commands had been
saved to the history.
uuu. Bash now parses command substitutions according to Posix rules: parsing
the command contained in $() to find the closing delimiter.
vvv. Fixed a bug that caused traps on SIGCHLD set in a SIGCHLD handler to
not persist.
www. Fixed a bug that didn't allow SIGCHLD to interrupt the `wait' builtin
as Posix specifies.
xxx. Invalid numeric arguments to shell builtins no longer cause the shell to
short-circuit any executing compound command.
yyy. Fixed a bug that caused the exit status to be lost when `break' was
used to short-circuit a loop's execution.
zzz. Fixed a bug that caused stray ^? characters to be left in expansions of
"${array[*]}".
aaaa. Bash now prints better error messages for here documents terminated by
EOF and for identifying the incorrect token in an invalid arithmetic
expression.
bbbb. Fixed a bug in the variable length word expansion that caused it to
incorrectly calculate the number of multibyte characters.
cccc. Fixed a race condition that could result in the top-level shell setting
the terminal's process group to an incorrect value if the process
group was changed by a child of a child of the shell.
dddd. Fixed a bug that caused here documents belonging to commands within a
compound command to be displayed in a syntactially-incorrect form, which
prevented them from being re-read as input.
eeee. The shell displays more warnings about failures to set the locale.
ffff. Fixed a bug that caused the body of a here-document to not be saved to
the history list.
gggg. Fixed a bug that caused configure to incorrectly conclude that FreeBSD
had /dev/fd available, resulting in problems with process substitution.
2. Changes to Readline
a. Fixed a number of redisplay errors in environments supporting multibyte
characters.
b. Fixed bugs in vi command mode that caused motion commands to inappropriately
set the mark.
c. When using the arrow keys in vi insertion mode, readline allows movement
beyond the current end of the line (unlike command mode).
d. Fixed bugs that caused readline to loop when the terminal has been taken
away and reads return -1/EIO.
e. Fixed bugs in redisplay occurring when displaying prompts containing
invisible characters.
f. Fixed a bug that caused the completion append character to not be reset to
the default after an application-specified completion function changed it.
g. Fixed a problem that caused incorrect positioning of the cursor while in
emacs editing mode when moving forward at the end of a line while using
a locale supporting multibyte characters.
h. Fixed an off-by-one error that caused readline to drop every 511th
character of buffered input.
i. Fixed a bug that resulted in SIGTERM not being caught or cleaned up.
j. Fixed redisplay bugs caused by multiline prompts with invisible characters
or no characters following the final newline.
k. Fixed redisplay bug caused by prompts consisting solely of invisible
characters.
l. Fixed a bug in the code that buffers characters received very quickly in
succession which caused characters to be dropped.
m. Fixed a bug that caused readline to reference uninitialized data structures
if it received a SIGWINCH before completing initialzation.
n. Fixed a bug that caused the vi-mode `last command' to be set incorrectly
and therefore unrepeatable.
o. Fixed a bug that caused readline to disable echoing when it was being used
with an output file descriptor that was not a terminal.
p. Readline now blocks SIGINT while manipulating internal data structures
during redisplay.
q. Fixed a bug in redisplay that caused readline to segfault when pasting a
very long line (over 130,000 characters).
r. Fixed bugs in redisplay when using prompts with no visible printing
characters.
3. New Features in Bash
a. When using substring expansion on the positional parameters, a starting
index of 0 now causes $0 to be prefixed to the list.
b. The `help' builtin now prints its columns with entries sorted vertically
rather than horizontally.
c. There is a new variable, $BASHPID, which always returns the process id of
the current shell.
d. There is a new `autocd' option that, when enabled, causes bash to attempt
to `cd' to a directory name that is supplied as the first word of a
simple command.
e. There is a new `checkjobs' option that causes the shell to check for and
report any running or stopped jobs at exit.
f. The programmable completion code exports a new COMP_TYPE variable, set to
a character describing the type of completion being attempted.
g. The programmable completion code exports a new COMP_KEY variable, set to
the character that caused the completion to be invoked (e.g., TAB).
h. If creation of a child process fails due to insufficient resources, bash
will try again several times before reporting failure.
i. The programmable completion code now uses the same set of characters as
readline when breaking the command line into a list of words.
j. The block multiplier for the ulimit -c and -f options is now 512 when in
Posix mode, as Posix specifies.
k. Changed the behavior of the read builtin to save any partial input received
in the specified variable when the read builtin times out. This also
results in variables specified as arguments to read to be set to the empty
string when there is no input available. When the read builtin times out,
it returns an exit status greater than 128.
l. The shell now has the notion of a `compatibility level', controlled by
new variables settable by `shopt'. Setting this variable currently
restores the bash-3.1 behavior when processing quoted strings on the rhs
of the `=~' operator to the `[[' command.
m. The `ulimit' builtin now has new -b (socket buffer size) and -T (number
of threads) options.
n. The -p option to `declare' now displays all variable values and attributes
(or function values and attributes if used with -f).
o. There is a new `compopt' builtin that allows completion functions to modify
completion options for existing completions or the completion currently
being executed.
p. The `read' builtin has a new -i option which inserts text into the reply
buffer when using readline.
q. A new `-E' option to the complete builtin allows control of the default
behavior for completion on an empty line.
r. There is now limited support for completing command name words containing
globbing characters.
s. Changed format of internal help documentation for all builtins to roughly
follow man page format.
t. The `help' builtin now has a new -d option, to display a short description,
and a -m option, to print help information in a man page-like format.
u. There is a new `mapfile' builtin to populate an array with lines from a
given file.
v. If a command is not found, the shell attempts to execute a shell function
named `command_not_found_handle', supplying the command words as the
function arguments.
w. There is a new shell option: `globstar'. When enabled, the globbing code
treats `**' specially -- it matches all directories (and files within
them, when appropriate) recursively.
x. There is a new shell option: `dirspell'. When enabled, the filename
completion code performs spelling correction on directory names during
completion.
y. The `-t' option to the `read' builtin now supports fractional timeout
values.
z. Brace expansion now allows zero-padding of expanded numeric values and
will add the proper number of zeroes to make sure all values contain the
same number of digits.
aa. There is a new bash-specific bindable readline function: `dabbrev-expand'.
It uses menu completion on a set of words taken from the history list.
bb. The command assigned to a key sequence with `bind -x' now sets two new
variables in the environment of the executed command: READLINE_LINE_BUFFER
and READLINE_POINT. The command can change the current readline line
and cursor position by modifying READLINE_LINE_BUFFER and READLINE_POINT,
respectively.
cc. There is a new &>> redirection operator, which appends the standard output
and standard error to the named file.
dd. The parser now understands `|&' as a synonym for `2>&1 |', which redirects
the standard error for a command through a pipe.
ee. The new `;&' case statement action list terminator causes execution to
continue with the action associated with the next pattern in the
statement rather than terminating the command.
ff. The new `;;&' case statement action list terminator causes the shell to
test the next set of patterns after completing execution of the current
action, rather than terminating the command.
gg. The shell understands a new variable: PROMPT_DIRTRIM. When set to an
integer value greater than zero, prompt expansion of \w and \W will
retain only that number of trailing pathname components and replace
the intervening characters with `...'.
hh. There are new case-modifying word expansions: uppercase (^[^]) and
lowercase (,[,]). They can work on either the first character or
array element, or globally. They accept an optional shell pattern
that determines which characters to modify. There is an optionally-
configured feature to include capitalization operators.
ii. The shell provides associative array variables, with the appropriate
support to create, delete, assign values to, and expand them.
jj. The `declare' builtin now has new -l (convert value to lowercase upon
assignment) and -u (convert value to uppercase upon assignment) options.
There is an optionally-configurable -c option to capitalize a value at
assignment.
kk. There is a new `coproc' reserved word that specifies a coprocess: an
asynchronous command run with two pipes connected to the creating shell.
Coprocs can be named. The input and output file descriptors and the
PID of the coprocess are available to the calling shell in variables
with coproc-specific names.
4. New Features in Readline
a. A new variable, rl_sort_completion_matches; allows applications to inhibit
match list sorting (but beware: some things don't work right if
applications do this).
b. A new variable, rl_completion_invoking_key; allows applications to discover
the key that invoked rl_complete or rl_menu_complete.
c. The functions rl_block_sigint and rl_release_sigint are now public and
available to calling applications who want to protect critical sections
(like redisplay).
d. The functions rl_save_state and rl_restore_state are now public and
available to calling applications; documented rest of readline's state
flag values.
e. A new user-settable variable, `history-size', allows setting the maximum
number of entries in the history list.
f. There is a new implementation of menu completion, with several improvements
over the old; the most notable improvement is a better `completions
browsing' mode.
g. The menu completion code now uses the rl_menu_completion_entry_function
variable, allowing applications to provide their own menu completion
generators.
h. There is support for replacing a prefix of a pathname with a `...' when
displaying possible completions. This is controllable by setting the
`completion-prefix-display-length' variable. Matches with a common prefix
longer than this value have the common prefix replaced with `...'.
i. There is a new `revert-all-at-newline' variable. If enabled, readline will
undo all outstanding changes to all history lines when `accept-line' is
executed.
------------------------------------------------------------------------------
This document details the changes between this version, bash-3.2-release,
and the previous version, bash-3.2-beta.
1. Changes to Bash
a. Fixed a bug that caused the temporary environment passed to a command to
affect the shell's environment under certain circumstances.
b. Fixed a bug in the printf builtin that caused the %q format specifier to
ignore empty string arguments.
c. Improved multibyte character environment detection at configuration time.
d. Fixed a bug in the read builtin that left spurious escape characters in the
input after processing backslashes when assigning to an array variable.
2. Changes to Readline
a. Fixed a redisplay bug that occurred in multibyte-capable locales when the
prompt was one character longer than the screen width.
------------------------------------------------------------------------------
This document details the changes between this version, bash-3.2-beta,
and the previous version, bash-3.2-alpha.
1. Changes to Bash
a. Changed the lexical analyzer to treat locale-specific blank characters as
white space.
b. Fixed a bug in command printing to avoid confusion between redirections and
process substitution.
c. Fixed problems with cross-compiling originating from inherited environment
variables.
d. Added write error reporting to printf builtin.
e. Fixed a bug in the variable expansion code that could cause a core dump in
a multi-byte locale.
f. Fixed a bug that caused substring expansion of a null string to return
incorrect results.
g. BASH_COMMAND now retains its previous value while executing commands as the
result of a trap, as the documentation states.
2. Changes to Readline
a. Fixed a bug with prompt redisplay in a multi-byte locale to avoid redrawing
the prompt and input line multiple times.
b. Fixed history expansion to not be confused by here-string redirection.
c. Readline no longer treats read errors by converting them to newlines, as
it does with EOF. This caused partial lines to be returned from readline().
------------------------------------------------------------------------------
This document details the changes between this version, bash-3.2-alpha,
and the previous version, bash-3.1-release.
1. Changes to Bash
a. Fixed a source bug that caused the minimal configuration to not compile.
b. Fixed memory leaks in error handling for the `read' builtin.
c. Changed the [[ and (( compound commands to set PIPESTATUS with their exit
status.
d. Fixed some parsing problems with compound array assignments.
e. Added additional configuration changes for: NetBSD (incomplete multibyte
character support)
f. Fixed two bugs with local array variable creation when shadowing a variable
of the same name from a previous context.
g. Fixed the `read' builtin to restore the correct set of completion functions
if a timeout occurs.
h. Added code to defer the initialization of HISTSIZE (and its stifling of the
history list) until the history file is loaded, allowing a startup file to
override the default value.
i. Tightened up the arithmetic expression parsing to produce better error
messages when presented with invalid operators.
j. Fixed the cross-compilation support to build the signal list at shell
invocation rather than compile time if cross-compiling.
k. Fixed multibyte support for non-gcc compilers (or compilers that do not
allow automatic array variable sizing based on a non-constant value).
l. Several fixes to the code that manages the list of terminated jobs and
their exit statuses, and the list of active and recently-terminated jobs
to avoid pid aliasing/wraparound and allocation errors.
m. Fixed a problem that allowed scripts to die due to SIGINT while waiting
for children, even when started in the background or otherwise ignoring
SIGINT.
n. Fixed a bug that caused shells invoked as -/bin/bash from not being
recognized as login shells.
o. Fixed a problem that caused shells in the background to give the terminal
to a process group other than the foreground shell process group.
p. Fixed a problem with extracting the `varname' in ${#varname}.
q. Fixed the code that handles SIGQUIT to not exit immediately -- thereby
calling functions that may not be called in a signal handler context --
but set a flag and exit afterward (like SIGINT).
r. Changed the brace expansion code to skip over braces that don't begin a
valid matched brace expansion construct.
s. Fixed `typeset' and `declare' to not require that their shell function
operands to be valid shell identifiers.
t. Changed `test' to use access(2) with a temporary uid/euid swap when testing
file attributes and running setuid, and access(2) in most other cases.
u. Changed completion code to not attempt command name completion on a line
consisting solely of whitespace when no_empty_command_completion is set.
v. The `hash' builtin now prints nothing in posix mode when the hash table is
empty, and prints a message to that effect to stdout instead of stderr
when not in posix mode.
w. Fixed a bug in the extended pattern matching code that caused it to fail to
match periods with certain patterns.
x. Fixed a bug that caused the shell to dump core when performing filename
generation in directories with thousands of files.
y. Returned to the original Bourne shell rules for parsing ``: no recursive
parsing of embedded quoted strings or ${...} constructs.
z. The inheritence of the DEBUG, RETURN, and ERR traps is now dependent only
on the settings of the `functrace' and `errtrace' shell options, rather
than whether or not the shell is in debugging mode.
aa. Fixed a problem with $HOME being converted to ~ in the expansion of
members of the DIRSTACK array.
bb. Fixed a problem with quoted arguments to arithmetic expansions in certain
constructs.
cc. The command word completion code now no longer returns matching directories
while searching $PATH.
dd. Fixed a bug with zero-padding and precision handling in snprintf()
replacement.
ee. Fixed a bug that caused the command substitution code not to take embedded
shell comments into account.
ff. Fixed a bug that caused $((...);(...)) to be misinterpreted as an
arithmetic substitution.
gg. Fixed a bug in the prompt expansion code that inappropriately added a
\001 before a \002 under certain circumstances.
hh. Fixed a bug that caused `unset LANG' to not properly reset the locale
(previous versions would set the locale back to what it was when bash
was started rather than the system's "native" locale).
ii. Fixed a bug that could cause file descriptors > 10 to not be closed even
when closed explicitly by a script.
jj. Fixed a bug that caused single quotes to be stripped from ANSI-C quoting
inside double-quoted command substitutions.
kk. Fixed a bug that could cause core dumps when `return' was executed as the
last element of a pipeline inside a shell function.
ll. Fixed a bug that caused DEBUG trap strings to overwrite commands stored in
the jobs list.
2. Changes to Readline
a. Fixed a problem that caused segmentation faults when using readline in
callback mode and typing consecutive DEL characters on an empty line.
b. Fixed several redisplay problems with multibyte characters, all having to
do with the different code paths and variable meanings between single-byte
and multibyte character redisplay.
c. Fixed a problem with key sequence translation when presented with the
sequence \M-\C-x.
d. Fixed a problem that prevented the `a' command in vi mode from being
undone and redone properly.
e. Fixed a problem that prevented empty inserts in vi mode from being undone
properly.
f. Fixed a problem that caused readline to initialize with an incorrect idea
of whether or not the terminal can autowrap.
g. Fixed output of key bindings (like bash `bind -p') to honor the setting of
convert-meta and use \e where appropriate.
h. Changed the default filename completion function to call the filename
dequoting function if the directory completion hook isn't set. This means
that any directory completion hooks need to dequote the directory name,
since application-specific hooks need to know how the word was quoted,
even if no other changes are made.
i. Fixed a bug with creating the prompt for a non-interactive search string
when there are non-printing characters in the primary prompt.
j. Fixed a bug that caused prompts with invisible characters to be redrawn
multiple times in a multibyte locale.
k. Fixed a bug that could cause the key sequence scanning code to return the
wrong function.
l. Fixed a problem with the callback interface that caused it to fail when
using multi-character keyboard macros.
m. Fixed a bug that could cause a core dump when an edited history entry was
re-executed under certain conditions.
n. Fixed a bug that caused readline to reference freed memory when attmpting
to display a portion of the prompt.
3. New Features in Bash
a. Changed the parameter pattern replacement functions to not anchor the
pattern at the beginning of the string if doing global replacement - that
combination doesn't make any sense.
b. When running in `word expansion only' mode (--wordexp option), inhibit
process substitution.
c. Loadable builtins now work on MacOS X 10.[34].
d. Shells running in posix mode no longer set $HOME, as POSIX requires.
e. The code that checks for binary files being executed as shell scripts now
checks only for NUL rather than any non-printing character.
f. Quoting the string argument to the [[ command's =~ operator now forces
string matching, as with the other pattern-matching operators.
4. New Features in Readline
a. Calling applications can now set the keyboard timeout to 0, allowing
poll-like behavior.
b. The value of SYS_INPUTRC (configurable at compilation time) is now used as
the default last-ditch startup file.
c. The history file reading functions now allow windows-like \r\n line
terminators.
------------------------------------------------------------------------------
This document details the changes between this version, bash-3.1-release,
and the previous version, bash-3.1-rc2.
1. Changes to Readline
a. Several changes to the multibyte redisplay code to fix problems with
prompts containing invisible characters.
------------------------------------------------------------------------------
This document details the changes between this version, bash-3.1-rc2,
and the previous version, bash-3.1-rc1.
1. Changes to Bash
a. Fixed a bug that caused a DEBUG trap to overwrite a command string that's
eventually attached to a background job.
b. Changed some code so that filenames with leading tildes with spaces in the
name aren't tilde-expanded by the bash completion code.
c. Fixed a bug that caused the pushd builtin to fail to change to
directories with leading `-'.
d. Fixed a small memory leak in the programmable completion code.
2. Changes to Readline
a. Fixed a redisplay bug caused by moving the cursor vertically to a line
with invisible characters in the prompt in a multibyte locale.
b. Fixed a bug that could cause the terminal special chars to be bound in the
wrong keymap in vi mode.
3. New Features in Bash
a. If compiled for strict POSIX conformance, LINES and COLUMNS may now
override the true terminal size.
4. New Features in Readline
a. A new external application-controllable variable that allows the LINES
and COLUMNS environment variables to set the window size regardless of
what the kernel returns.
------------------------------------------------------------------------------
This document details the changes between this version, bash-3.1-rc1,
and the previous version, bash-3.1-beta1.
1. Changes to Bash
a. Fixed a bug that could cause core dumps due to accessing the current
pipeline while in the middle of modifying it.
b. Fixed a bug that caused pathnames with backslashes still quoting characters
to be passed to opendir().
c. Command word completion now obeys the setting of completion-ignore-case.
d. Fixed a problem with redirection that caused file descriptors greater than
2 to be inappropriately marked as close-on-exec.
e. In Posix mode, after `wait' is called to wait for a particular process
explicitly, that process is removed from the list of processes known to
the shell, and subsequent attempts to wait for it return errors.
f. Fixed a bug that caused extended pattern matching to incorrectly scan
backslash-escaped pattern characters.
g. Fixed a synchronization problem that could cause core dumps when handling
a SIGWINCH.
h. Fixed a bug that caused an unmatched backquote to be accepted without an
error when processing here documents.
i. Fixed a small memory leak in the `cd' builtin.
j. Fix for MacOS X so it gets the values for the HOSTTYPE, MACHTYPE, and
OSTYPE variables at build time, to support universal binaries.
k. Fixed a bug that could cause an exit trap to return the exit status of
the trap command rather than the status as it was before the trap was
run as the shell's exit status.
2. New Features in Bash
3. Changes to Readline
a. Fixed a bug that caused reversing the incremental search direction to
not work correctly.
b. Fixed the vi-mode `U' command to only undo up to the first time insert mode
was entered, as Posix specifies.
c. Fixed a bug in the vi-mode `r' command that left the cursor in the wrong
place.
4. New Features in Readline
a. New application-callable auxiliary function, rl_variable_value, returns
a string corresponding to a readline variable's value.
b. When parsing inputrc files and variable binding commands, the parser
strips trailing whitespace from values assigned to boolean variables
before checking them.
------------------------------------------------------------------------------
This document details the changes between this version, bash-3.1-beta1,
and the previous version, bash-3.1-alpha1.
1. Changes to Bash
a. Added some system-specific signal names.
b. Fixed a typo in the ulimit builtin to make `x' the right option to
maniuplate the limit on file locks.
c. Fixed a problem with using += to append to index 0 of an array variable
when not using subscript syntax.
d. A few changes to configure.in to remove calls to obsolete or outdated
macros.
e. Make sure changes to variables bash handles specially (e.g., LC_ALL) are
made when the variable is set in the temporary environment to a command.
f. Make sure changes to variables bash handles specially (e.g., LC_ALL) are
made when the variable is modified using `printf -v'.
g. The export environment is now remade on cygwin when HOME is changed, so
DLLs bash is linked against pick up the new value. This fixes problems
with tilde expansion when linking against and already-installed readline.
h. Small fix to the logic for performing tilde expansion in posix mode, so
expansion on the right-hand side of an assignment statement takes place.
i. Fixed a bug that prevented redirections associated with a shell function
from being executed when in a subshell.
j. Fixed `source' and `.' builtins to not require an executable file when
searching $PATH for a file to source.
k. Fixed a bug that caused incorrect word splitting in a function when IFS
was declared local, then unset.
l. Fixed a problem with the `kill' builtin that prevented sending signals
to a process group under certain circumstances when providing a pid < 0.
m. When in POSIX mode, `pwd' now checks that the value it prints is the same
directory as `.', even when displaying $PWD.
n. Fixed a problem with the `read' builtin when reading a script from standard
input and reading data from the same file.
o. Fixed a problem with the `type' and `command' builtins that caused absolute
pathnames to be displayed incorrectly.
p. Some changes to the `bg' builtin for POSIX conformance.
q. The `fc' builtin now removes the `fc' command that caused it to invoke an
editor on specified history entries from the history entirely, rather than
simply ignoring it.
r. When in POSIX mode, the `v' command in vi editing mode simply invokes vi
on the current command, rather than checking $FCEDIT and $EDITOR.
s. Fixed a small memory leak in the pathname canonicalization code.
t. Fixed a bug that caused the expanded value of a $'...' string to be
incorrectly re-quoted if it occurred within a double-quoted ${...}
parameter expansion.
u. Restored default emacs-mode key binding of M-TAB to dynamic-complete-history.
v. Fixed a bug that caused core dumps when interrupting loops running builtins
on some systems.
w. Make sure that some of the functions bash provides replacements for are
not cpp defines.
x. The code that scans embedded commands for the parser (`...` and $(...)) is
now more aware of embedded comments and their effect on quoted strings.
y. Changed the `-n' option to the `history' builtin to not reset the number of
history lines read in the current session after reading the new lines from
the history file if the history is being appended when it is written to
the file, since the appending takes care of the problem that the adjustment
was intended to solve.
z. Improved the error message displayed when a shell script fails to execute
because the environment and size of command line arguments are too large.
aa. A small fix to make sure that $HISTCMD is evaluated whenever the shell is
saving commands to the history list, not just when HISTSIZE is defined.
2. Changes to Readline
a. The `change-case' command now correctly changes the case of multibyte
characters.
b. Changes to the shared library construction scripts to deal with Windows
DLL naming conventions for Cygwin.
c. Fixed the redisplay code to avoid core dumps resulting from a poorly-timed
SIGWINCH.
d. Fixed the non-incremental search code in vi mode to dispose of any current
undo list when copying a line from the history into the current editing
buffer.
e. The variable assignment code now ignores whitespace at the end of lines
when assigning to boolean variables.
f. The `C-w' binding in incremental search now understands multibyte
characters.
3. New Features in Bash
a. A new configuration option, `--enable-strict-posix-default', which will
build bash to be POSIX conforming by default.
4. New Features in Readline
a. If the rl_completion_query_items is set to a value < 0, readline never
asks the user whether or not to view the possible completions.
------------------------------------------------------------------------------
This document details the changes between this version, bash-3.1-alpha1,
and the previous version, bash-3.0-release.
1. Changes to Bash
a. Fixed a bug that caused bash to crash if referencing an unset local array.
b. Fixed a problem that caused tilde expansion to not be performed before
attempting globbing word completion.
c. Fixed an incompatibility so that a first argument to trap that's a valid
signal number will be trated as a signal rather than a command to execute.
d. Fixed ${#word} expansion to correctly compute the length of a string
containing multibyte characters.
e. Fixed a bug that caused bash to not pass the correct flags for signal
disposition to child processes.
f. Fixed a bug that caused `fc -l' to list one too many history entries.
g. Some fixes to `fc' for POSIX conformance.
h. Some fixes to job status display for POSIX conformance.
i. Fixed a bug that caused `command -v' to display output if a command was not
found -- it should be silent.
j. In POSIX mode, `type' and `command -[vV]' do not report non-executable
files, even if the shell will attempt to execute them.
k. Fixed a bug that caused the `==' operator to the [[ command to not attempt
extended pattern matching.
l. Fixed the brace expansion code to handle characters whose value exceeds 128.
m. Fixed `printf' to handle strings with a leading `\0' whose length is
non-zero.
n. Fixed a couple of problems with brace expansion where `${' was handled
incorrectly.
o. Fixed off-by-one error when calculating the upper bound of `offset' when
processing the ${array[@]:offset:length} expansion.
p. System-specific configuration changes for: FreeBSD 5.x, Interix, MacOS X
10.4, Linux 2.4+ kernels, Linux 3.x kernels, Dragonfly BSD, QNX 6.x,
Cygwin
q. Fixed a bug that caused the shell to ignore the status of the rightmost
command in a pipeline when the `pipefail' option was enabled.
r. Fixed a completion bug that caused core dumps when expanding a directory
name.
s. Fixed a bug that prevented `hash -d' from removing commands from the hash
table.
t. Fixed word splitting to avoid really bad quadratic performance when
expanding long lists.
u. Fixed a bug that caused negative offsets in substring expansion to use the
wrong values.
v. Fixed a bug in printf that caused it to not return failure on write errors.
w. Fixed a bug that caused commands in subshells to not be properly timed.
x. The shell parser no longer attempts to parse a compound assignment specially
unless in a position where an assignment statement is acceptable or parsing
arguments to a builtin that accepts assignment statements.
y. Fixed a problem that caused a `case' statement to be added to the history
incorrectly as a single command if the `case word' was on one line and the
`in' on another.
z. Fixed a problem that caused internal shell quoting characters to be
incorrectly quoted with backslashes under some circumstances.
aa. The shell now performs correct word splitting when IFS contains multibyte
characters.
bb. The mail checking code now resets the cached file information if the size
drops to 0, even if the times don't change.
cc. A completed command name that is found in $PATH as well as the name of a
directory in the current directory no longer has a slash appended in certain
circumstances: a single instance found in $PATH when `.' is not in $PATH,
and multiple instances found in $PATH, even when `.' is in $PATH.
dd. Incorporated tilde expansion into the word expansion code rather than as a
separately-called function, fixing some cases where it was performed
inappropriately (e.g., after the second `=' in an assignment statement or
in a double-quoted parameter expansion).
ee. Fixed several bugs encountered when parsing compound assignment statements,
so that compound assignments appearing as arguments to builtins are no
longer double-expanded.
ff. Fixed a bug in the command execution code that caused asynchronous commands
containing command substitutions to not put the terminal in the wrong
process group.
gg. Bash now handles the case where the WCONTINUED flag causes waitpid() to
return -1/EINVAL at runtime as well as configuration time.
hh. Fixed parser to generate an error when the pipeline `argument' to `!' or
`time' is NULL.
ii. The shell now takes a little more care when manipulating file descriptors
greater than 9 with the `exec' builtin.
jj. Fixed a bug that caused variable assignments preceding the `command' builtin
preceding a special builtin to be preserved after the command completed in
POSIX mode.
kk. Fixed a bug that allowed variables beginning with a digit to be created.
ll. Fixed a bug that caused a \ to be removed when parsing a $'...'
construct.
mm. A shell whose name begins with `-' will now be a restricted shell if the
remainder of the name indicates it should be restricted.
nn. Fixed a bug that could cause a core dump if FUNCNAME were changed or unset
during a function's execution.
oo. Fixed a bug that caused executing a `return' in a function to not execute
a RETURN trap. The RETURN trap is inherited by shell functions only if
function tracing is globally enabled or has been enabled for that function.
pp. Fixed cases where var[@] was not handled exactly like var, when var is a
scalar variable.
qq. Fixed a bug that caused the first character after a SIGINT to be discarded
under certain circumstances.
rr. Fixed exit status code so that a suspended job returns 128+signal as its
exit status (preventing commands after it in `&&' lists from being
executed).
ss. Fixed a bug that caused the shell parser state to be changed by executing
a shell function as a result of word completion.
tt. Fixed a long-standing bug that caused '\177' characters in variable
values to be discarded when expanded in double-quoted strings.
uu. Fixed a bug that caused $RANDOM to be re-seeded multiple times in a
subshell environment.
vv. Extensive changes to the job management code to avoid the pid-reuse and
pid-aliasing problems caused by retaining the exit status of too many jobs,
but still retain as many background job statuses as POSIX requires.
ww. Fixed a parser bug in processing \ that caused things like
((echo 5) \
(echo 6))
to not work correctly.
xx. `pwd -P' now sets $PWD to a directory name containing no symbolic links
when in posix mode, as POSIX requires.
yy. In posix mode, bash no longer sets $PWD to a name containing no symbolic
links if a directory is chosen from $CDPATH.
zz. The word splitting code now treats an IFS character that is not space,
tab, or newline and any adjacent IFS white space as a single delimiter, as
SUSv3/XPG6 require.
aaa. The `read' builtin now checks whether or not the number of fields read is
exactly the same as the number of variables instead of just assigning the
rest of the line (minus any trailing IFS white space) to the last
variable. This is what POSIX/SUS/XPG all require.
bbb. Fixed a bug that caused `read' to always check whether or not fd 0 was a
pipe, even when reading from another file descriptor.
ccc. Fixed a bug that caused short-circuiting of execution even if the return
value was being inverted.
ddd. Fixed a bug that caused a core dump while decoding \W escapes in PS1 if
PWD was unset.
eee. Fixed a bug in `read' that counted internal quoting characters for the
purposes of `read -n'.
fff. Fixed a bug so that a function definition in a pipeline causes a child
process to be forked at the right time.
ggg. Bash will not attempt to link against a readline library that doesn't
have rl_gnu_readline_p == 1.
hhh. Fixed a bug that caused `read' to consume one too many characters when
reading a fixed number of characters and the Nth character is a backslash.
iii. Fixed a bug that caused `unset' on variables in the temporary environment
to leave them set when `unset' completed.
jjj. Fixed a bug that caused bash to close fd 2 if an `exec' failed and the
shell didn't exit.
kkk. The completion code is more careful to not turn `/' or `///' into `//',
for those systems on which `//' has special meaning.
lll. Fixed a bug that caused command substitution in asynchronous commands to
close the wrong file descriptors.
mmm. The shell no longer prints status messages about terminated background
processes unless job control is active.
nnn. Fixed a bug that prevented multiple consecutive invocations of `history -s'
from adding all the commands to the history list.
ooo. Added a couple of changes to make arithmetic expansion more consistent in
all its contexts (still not perfect).
ppp. Fixed a bug that caused the parser to occasionally not find the right
terminating "`" in an old-style command substitution.
qqq. Fixed a bug that caused core dumps when the shell was reading its non-
interactive input from fd 0 and fd 0 was duplicated and restored using a
combination of `exec' (to save) and redirection (to restore).
rrr. Fixed a problem that caused loops in sourced scripts to not be cleaned
up properly when a `return' is executed.
sss. Change internal command substitution completion function to append a slash
to directory names in the command.
2. Changes to Readline
a. Fixed a bug that caused multiliine prompts to be wrapped and displayed
incorrectly.
b. Fixed a bug that caused ^P/^N in emacs mode to fail to display the current
line correctly.
c. Fixed a problem in computing the number of invisible characters on the first
line of a prompt whose length exceeds the screen width.
d. Fixed vi-mode searching so that failure preserves the current line rather
than the last line in the history list.
e. Fixed the vi-mode `~' command (change-case) to have the correct behavior at
end-of-line when manipulating multibyte characters.
f. Fixed the vi-mode `r' command (change-char) to have the correct behavior at
end-of-line when manipulating multibyte characters.
g. Fixed multiple bugs in the redisplay of multibyte characters: displaying
prompts longer than the screen width containing multibyte characters,
h. Fix the calculation of the number of physical characters in the prompt
string when it contains multibyte characters.
i. A non-zero value for the `rl_complete_suppress_append' variable now causes
no `/' to be appended to a directory name.
j. Fixed forward-word and backward-word to work when words contained
multibyte characters.
k. Fixed a bug in finding the delimiter of a `?' substring when performing
history expansion in a locale that supports multibyte characters.
l. Fixed a memory leak caused by not freeing the timestamp in a history entry.
m. Fixed a bug that caused "\M-x" style key bindings to not obey the setting
of the `convert-meta' variable.
n. Fixed saving and restoring primary prompt when prompting for incremental
and non-incremental searches; search prompts now display multibyte
characters correctly.
o. Fixed a bug that caused keys originally bound to self-insert but shadowed
by a multi-character key sequence to not be inserted.
p. Fixed code so rl_prep_term_function and rl_deprep_term_function aren't
dereferenced if NULL (matching the documentation).
q. Extensive changes to readline to add enough state so that commands
requiring additional characters (searches, multi-key sequences, numeric
arguments, commands requiring an additional specifier character like
vi-mode change-char, etc.) work without synchronously waiting for
additional input.
r. Lots of changes so readline builds and runs on MinGW.
s. Readline no longer tries to modify the terminal settings when running in
callback mode.
t. The Readline display code no longer sets the location of the last invisible
character in the prompt if the \[\] sequence is empty.
3. New Features in Bash
a. Bash now understands LC_TIME as a special variable so that time display
tracks the current locale.
b. BASH_ARGC, BASH_ARGV, BASH_SOURCE, and BASH_LINENO are no longer created
as `invisible' variables and may not be unset.
c. In POSIX mode, if `xpg_echo' option is enabled, the `echo' builtin doesn't
try to interpret any options at all, as POSIX requires.
d. The `bg' builtin now accepts multiple arguments, as POSIX seems to specify.
e. Fixed vi-mode word completion and glob expansion to perform tilde
expansion.
f. The `**' mathematic exponentiation operator is now right-associative.
g. The `ulimit' builtin has new options: -i (max number of pending signals),
-q (max size of POSIX message queues), and -x (max number of file locks).
h. A bare `%' once again expands to the current job when used as a job
specifier.
i. The `+=' assignment operator (append to the value of a string or array) is
now supported for assignment statements and arguments to builtin commands
that accept assignment statements.
j. BASH_COMMAND now preserves its value when a DEBUG trap is executed.
k. The `gnu_errfmt' option is enabled automatically if the shell is running
in an emacs terminal window.
l. New configuration option: --single-help-strings. Causes long help text
to be written as a single string; intended to ease translation.
m. The COMP_WORDBREAKS variable now causes the list of word break characters
to be emptied when the variable is unset.
n. An unquoted expansion of $* when $IFS is empty now causes the positional
parameters to be concatenated if the expansion doesn't undergo word
splitting.
o. Bash now inherits $_ from the environment if it appears there at startup.
p. New shell option: nocasematch. If non-zero, shell pattern matching ignores
case when used by `case' and `[[' commands.
q. The `printf' builtin takes a new option: -v var. That causes the output
to be placed into var instead of on stdout.
r. By default, the shell no longer reports processes dying from SIGPIPE.
s. Bash now sets the extern variable `environ' to the export environment it
creates, so C library functions that call getenv() (and can't use the
shell-provided replacement) get current values of environment variables.
4. New Features in Readline
a. The key sequence sent by the keypad `delete' key is now automatically
bound to delete-char.
b. A negative argument to menu-complete now cycles backward through the
completion list.
c. A new bindable readline variable: bind-tty-special-chars. If non-zero,
readline will bind the terminal special characters to their readline
equivalents when it's called (on by default).
d. New bindable command: vi-rubout. Saves deleted text for possible
reinsertion, as with any vi-mode `text modification' command; `X' is bound
to this in vi command mode.
------------------------------------------------------------------------------
This document details the changes between this version, bash-3.0-release,
and the previous version, bash-3.0-rc1.
1. Changes to Bash
a. Fixed a boundary overrun that could cause segmentation faults when the
completion code hands an incomplete construct to the word expansion
functions.
b. Changed posix mode behavior so that an error in a variable assignment
preceding a special builtin causes a non-interactive shell to exit.
c. Change the directory expansion portion of the completion code to not
expand embedded command substitutions if the directory name appears in
the file system.
d. Fixed a problem that caused `bash -r' to turn on restrictions before
reading the startup files.
e. Fixed a problem with the default operation of the `umask' builtin.
2. Changes to Readline
a. Fixed a problem with readline saving the contents of the current line
before beginning a non-interactive search.
b. Fixed a problem with EOF detection when using rl_event_hook.
c. Fixed a problem with the vi mode `p' and `P' commands ignoring numeric
arguments.
------------------------------------------------------------------------------
This document details the changes between this version, bash-3.0-rc1,
and the previous version, bash-3.0-beta1.
1. Changes to Bash
a. Fixed a bug that caused incorrect behavior when referecing element 0 of
an array using $array, element 0 was unset, and `set -u' was enabled.
b. System-specific changes for: SCO Unix 3.2, Tandem.
c. Fixed a bug that caused inappropriate word splitting when a variable was
expanded within a double-quoted string that also included $@.
d. Fixed a bug that caused `pwd' to not display anything in physical mode
when the file system had changed underneath the shell.
e. Fixed a bug in the pre- and post- increment and decrement parsing in the
expression evaluator that caused errors when the operands and corresponding
operators were separated by whitespace.
f. Fixed a bug that caused `history -p' to add an entry to the history list,
counter to the documentation. (Keeps the history expansions invoked by
emacs-mode command line editing from doing that as well.)
g. Fixed a bug that could cause a core dump if `cd' is asked to print out a
pathname longer than PATH_MAX characters.
h. Fixed a bug that caused jobs to be put into the wrong process group under
some circumstances after enabling job control with `set -m'.
i. `unalias' now returns failure if no alias name arguments are supplied.
j. Documented the characters not allowed to appear in an alias name.
k. $* is no longer expanded as if in double quotes when it appears in the
body of a here document, as the SUS seems to require.
l. The `bashbug' script now uses a directory in $TMPDIR for exclusive
access rather than trying to guess how the underlying OS provides for
secure temporary file creation.
m. Fixed a few problems with `cd' and `pwd' when asked to operate on pathnames
longer than PATH_MAX characters.
n. Fixed a memory leak caused when creating multiple local array variables
with identical names.
o. Fixed a problem with calls to getcwd() so that bash now operates better
when the full pathname to the current directory is longer than PATH_MAX
bytes.
p. The `trap' builtin now reports an error if a single non-signal argument
is specified.
q. Fixed a bug that caused `umask' to not work correctly when presented
with a mask of all 0s.
r. When `getopts' reaches the end of options, OPTARG is unset, as POSIX
appears to specify.
s. Interactive mode now depends on whether or not stdin and stderr are
connected to a tty; formerly it was stdin and stdout. POSIX requires
this.
t. Fixed vi-mode completion to work more as POSIX specifies (e.g., doing the
right kind of filename generation).
2. Changes to Readline
a. Fixed a problem that could cause readline to refer to freed memory when
moving between history lines while doing searches.
b. Improvements to the code that expands and displays prompt strings
containing multibyte characters.
c. Fixed a problem with vi-mode not correctly remembering the numeric argument
to the last `c'hange command for later use with `.'.
d. Fixed a bug in vi-mode that caused multi-digit count arguments to work
incorrectly.
e. Fixed a problem in vi-mode that caused the last text modification command
to not be remembered across different command lines.
f. Fixed problems with changing characters and changing case at the end of
the line.
3. New Features in Bash
a. The `jobs', `kill', and `wait' builtins now accept job control notation
even if job control is not enabled.
b. The historical behavior of `trap' that allows a missing `action' argument
to cause each specified signal's handling to be reset to its default is
now only supported when `trap' is given a single non-option argument.
4. New Features in Readline
a. When listing completions, directories have a `/' appended if the
`mark-directories' option has been enabled.
------------------------------------------------------------------------------
This document details the changes between this version, bash-3.0-beta1,
and the previous version, bash-3.0-alpha.
1. Changes to Bash
a. Fixes to build correctly when arrays are not compiled into the shell.
b. Fixed command substitution to run any exit trap defined in the command
substitution before returning; the exit trap is not inherited from the
calling shell.
c. Fixes to process group synchronization code so that every child process
attempts to set the terminal's process group; fixes some synchronization
problems on Linux kernels that schedule the child to always run before
the parent.
d. Fixed processing of octal and hex constants in printf builtin for POSIX.2
compliance.
e. Fixed a couple of core dumps in the pattern removal code.
f. Fixes to the array subrange extraction code to deal better with sparse
arrays.
g. Parser errors and other errors that result in the shell exiting now cause
the exit trap to be run.
h. Change the command substitution completion functions to not append any
closing quote, because it would be inserted a closing "`" or ")".
i. Fix history initialization so assignments to $histchars made in startup
files are honored.
j. If an exit trap does not contain a call to `exit', the shell now uses
the exit status of the last command executed before the trap as the exit
status of the shell.
k. The parser now prompts with $PS2 if it reads a newline while parsing a
compound array assignment statement.
l. When performing a compound array assignment, the parser doesn't treat
words of the form [index]=value as assignments if they're the result of
expansions.
m. Fixed a bug that caused `return' executed in a trap command to make the
shell think it was still running the trap.
n. Fixed the value of errno set by the pathname canonicalization functions.
o. Changed the grammar so that `time' alone on a line times a null command
rather than being a syntax error.
p. The pattern substitution code no longer performs quote removal on the
pattern before trying to match it, as the pattern removal functions do.
q. Fixed a bug that could cause core dumps when checking whether a quoted
command name was being completed.
r. Fixes to the pattern removal and pattern replacement expansions to deal
with multibyte characters better (and faster).
s. Fix to the substring expansion (${param:off[:len]}) to deal with (possibly
multibyte) characters instead of raw bytes.
t. Fixed a bug that caused some key bindings set in an inputrc to be ignored
at shell startup.
u. Fixed a bug that caused unsetting a local variable within a function to
not work correctly.
v. Fixed a bug that caused invalid variables to be created when using
`read -a'.
w. Fixed a bug that caused "$@" to expand incorrectly when used as the right
hand side of a parameter expansion such as ${word:="$@"} if the first
character of $IFS was not a space.
x. Fixed a slight cosmetic problem when printing commands containing a
`>&word' redirection.
y. Fixed a problem that could cause here documents to not be created correctly
if the system temporary directory did not allow writing.
2. Changes to Readline
a. Change to history expansion functions to treat `^' as equivalent to word
one, as the documention states.
b. Some changes to the display code to improve display and redisplay of
multibyte characters.
c. Changes to speed up the multibyte character redisplay code.
d. Fixed a bug in the vi-mode `E' command that caused it to skip over the
last character of a word if invoked while point was on the word's
next-to-last character.
e. Fixed a bug that could cause incorrect filename quoting when
case-insensitive completion was enabled and the word being completed
contained backslashes quoting word break characters.
f. Fixed a bug in redisplay triggered when the prompt string contains
invisible characters.
g. Fixed some display (and other) bugs encountered in multibyte locales
when a non-ascii character was the last character on a line.
h. Fixed some display bugs caused by multibyte characters in prompt strings.
i. Fixed a problem with history expansion caused by non-whitespace characters
used as history word delimiters.
3. New Features in Bash
a. printf builtin understands two new escape sequences: \" and \?.
b. `echo -e' understands two new escape sequences: \" and \?.
c. The GNU `gettext' package and libintl have been integrated; the shell's
messages can be translated into different languages.
d. The `\W' prompt expansion now abbreviates $HOME as `~', like `\w'.
e. The error message printed when bash cannot open a shell script supplied
as argument 1 now includes the name of the shell, to better identify
the error as coming from bash.
4. New Features in Readline
a. New application variable, rl_completion_quote_character, set to any
quote character readline finds before it calls the application completion
function.
b. New application variable, rl_completion_suppress_quote, settable by an
application completion function. If set to non-zero, readline does not
attempt to append a closing quote to a completed word.
c. New application variable, rl_completion_found_quote, set to a non-zero
value if readline determines that the word to be completed is quoted.
Set before readline calls any application completion function.
d. New function hook, rl_completion_word_break_hook, called when readline
needs to break a line into words when completion is attempted. Allows
the word break characters to vary based on position in the line.
e. New bindable command: unix-filename-rubout. Does the same thing as
unix-word-rubout, but adds `/' to the set of word delimiters.
------------------------------------------------------------------------------
This document details the changes between this version, bash-3.0-alpha,
and the previous version, bash-2.05b-release.
1. Changes to Bash
a. Fixes so that the shell will compile without some of the default options
defined.
b. Fixed an error message that did not pass enough arguments to printf.
c. Fixed a bug that caused input redirection to a builtin inside a script
being read from standard input to result in the rest of the already-
read and buffered script to be discarded.
d. Fixed a bug that caused subshell initialization to close the file
descriptor from which the shell was reading a script under certain
circumstances.
e. Fixed a bug that caused the shell to not advance a string pointer over
a null wide character when doing string operations.
f. Fixed the internal logout code so that shells that time out waiting for
input (using $TMOUT) run ~/.bash_logout.
g. Portability and configuration changes for: cygwin, HP/UX, GNU/FreeBSD.
h. The parser no longer adds implicit double quotes to ((...)) arithmetic
commands.
i. The ((...)) arithmetic command evaluation code was fixed to not dump core
when the expanded string is null.
j. The ((...)) arithmetic command evaluation code was fixed to not perform
variable assignments while expanding the expression.
k. Fixed a bug that caused word splitting to be performed incorrectly when
IFS is set, but null.
l. Fixed a bug in brace expansion that caused a quoted `$' preceding an
open brace to inhibit brace expansion.
m. Fixed a bug that caused a leading `-' in the shell's name to cause it to
not be recognized as a restricted shell.
n. Fixed a bug in the arithmetic evaluation code that could cause longjmps
to an invalid location and result in a core dump.
o. Fixed a bug in the calculation of how many history lines are new in a
single shell session when reading new history lines from a file with
`history -n'.
p. Fixed a bug in pathname canonicalization that caused the shell to dump
core when presented with a pathname longer than PATH_MAX.
q. Fixed the parser so that it doesn't try to compare a char variable to
EOF, which fails when chars are unsigned.
r. Fixed a bug in the simple command execution code that caused occasional
core dumps.
s. The shell does a better job of saving any partial parsing state during
operations which cause a command to be executed while a line is being
entered and parsed.
t. The completion code now splits words more like the expansion code when
$IFS is used to split.
u. The locale code does a better job of recomputing the various locale
variable values when LC_ALL is unset.
v. The programmable completion code does a better job of dequoting expanded
word lists before comparing them against the word to be matched.
w. The shell no longer seg faults if the expanded value of $PS4 is null
and `set -x' is enabled.
x. Fixed a bug that caused core dumps when a here string expanded to NULL.
y. The mail checking code now makes sure the mailbox is bigger before
reporting the existence of new mail.
z. The parser does not try to expand $'...' and $"..." when the appear
within double quotes unless the `extquote' option has been enabled with
`shopt'. For backwards compatibility, it is enabled by default.
aa. Fixed a bug that caused `for x; do ...' and `select x; do ... to use
$@ instead of "$@" for the implicit list of arguments.
bb. Fixed a bug that caused a subshell of a restricted shell (e.g., one
spawned to execute a pipeline) to not exit immediately if attempting
to use a command containing a slash.
cc. Fixed a problem with empty replacements for a pattern that doesn't match
when performing ${param/word/} expansion.
dd. Word expansions performed while expanding redirections no longer search
a command's temporary environment to expand variable values.
ee. Improvements to the alias expansion code when expanding subsequent words
because an aliase's value ends with a space.
ff. `cd -' now prints the current working directory after a successful chdir
even when the shell is not interactive, as the standard requires.
gg. The shell does a better job of ensuring a child process dies of SIGINT
before resending SIGINT to itself.
hh. The arithmetic expansion variable assignment code now does the right
thing when assigning to `special' variables like OPTIND.
ii. When history expansion verification is enabled, the bash readline helper
functions that do history expansion on the current line don't print
the results.
jj. Fixed bugs with multiple consecutive alias expansion when one of the
expansions ends with a space.
kk. Fixed a problem in the programmable completion code that could cause core
dumps when trying to initialize a set of possible completions from a
list of variables.
ll. The \[ and \] escape characters are now ignored when decoding the prompt
string if the shell is started with editing disabled.
mm. Fixed a bug that could leave extra characters in a string when doing
quoted null character removal.
nn. Command substitution and other subshell operations no longer reset the
line number (aids the bash debugger).
oo. Better line number management when executing simple commands, conditional
commands, for commands, and select commands.
pp. The globbing code now uses malloc, with its better failure properties,
rather than alloca().
qq. Fixed a bug that caused expansions like #{a[2]:=value} to create the
appropriate array element instead of a variable named `a[2]'.
rr. Fixed a bug in the handling of a `?(...)' pattern immediately following
a `*' when extglob is enabled.
ss. Fixed a bug that caused a `return' invoked in an exit trap when exit is
invoked in a function to misbehave.
tt. Fixed a bug that caused CTLESC and CTLNUL characters to not be escaped
by the internal shell string quoting functions.
uu. Fixed a bug that caused quoted null characters in an expanded word list
to be inappropriately assigned to an array variable when using `read -a'.
vv. Fixed a bug that caused redirections accompanying a null command to persist
in the current shell.
ww. Fixed a bug that caused the prompt to be printed when the shell was
expanding a multiline alias.
xx. Fixed a bug that resulted in core dumps when the completion for a command
changed the compspec.
yy. Fixed a bug that caused evaluation of programmable completions to print
notifications of completed jobs.
zz. Bash now disables line editing when $EMACS == `t' and $TERM == `dumb'
(which is what emacs shell windows do).
aaa. In posix mode, `kill -l' causes signal names to be displayed without
a leading `SIG'.
bbb. Clear error flag on standard output so it doesn't persist across multiple
builtin commands.
ccc. In posix mode, `alias' displays alias values without the leading `alias',
so the output cannot be used as subsequent input.
ddd. In posix mode, the `trap' builtin doesn't check whether or not its
first argument is a signal specification and revert the signal handling
to its original disposition if it is.
eee. Fixed several bugs in the handling of "$*" and "${array[*]}" by the
pattern substitution and removal expansions.
fff. Fixed several problems with the handling of ${array[@]}, ${array[*]},
$@, and $* by the indirect variable expansion code.
ggg. Fixed a bug that did not allow `time' to be aliased.
hhh. Improved the mail checking code so it won't check (and possibly cause an
NFS file system mount) until MAILPATH or MAIL is given a value -- there
is no default if DEFAULT_MAIL_DIRECTORY is not defined at compile time.
(It is computed by configure, but can be #undef'd in config-bot.h.)
iii. If the `chkwinsize' option is enabled, the shell checks for window size
changes if a child process exits due to a signal.
jjj. Removed the attempts to avoid adding a slash at the end of a completed
executable name if there was a directory with the same name in the
current directory.
kkk. Fixed PATH lookup code so it treats the permission bits separately for
owner, group, and other, rather than checking them all.
lll. Fixed the locale code to reset the parser's idea of the character class
, which controls how it splits tokens, when the locale changes.
mmm. The shell now binds its special readline functions and key bindings only
if the user's inputrc file has not already bound them.
nnn. The shell now reports on processes that dump core due to signals when
invoked as `-c command'.
2. Changes to Readline
a. Fixes to avoid core dumps because of null pointer references in the
multibyte character code.
b. Fix to avoid infinite recursion caused by certain key combinations.
c. Fixed a bug that caused the vi-mode `last command' to be set incorrectly.
d. Readline no longer tries to read ahead more than one line of input, even
when more is available.
e. Fixed the code that adjusts the point to not mishandle null wide
characters.
f. Fixed a bug in the history expansion `g' modifier that caused it to skip
every other match.
g. Fixed a bug that caused the prompt to overwrite previous output when the
output doesn't contain a newline and the locale supports multibyte
characters. This same change fixes the problem of readline redisplay
slowing down dramatically as the line gets longer in multibyte locales.
h. History traversal with arrow keys in vi insertion mode causes the cursor
to be placed at the end of the new line, like in emacs mode.
i. The locale initialization code does a better job of using the right
precedence and defaulting when checking the appropriate environment
variables.
j. Fixed the history word tokenizer to handle <( and >( better when used as
part of bash.
k. The overwrite mode code received several bug fixes to improve undo.
l. Many speedups to the multibyte character redisplay code.
m. The callback character reading interface should not hang waiting to read
keyboard input.
n. Fixed a bug with redoing vi-mode `s' command.
o. The code that initializes the terminal tracks changes made to the terminal
special characters with stty(1) (or equivalent), so that these changes
are reflected in the readline bindings. New application-callable function
to make it work: rl_tty_unset_default_bindings().
p. Fixed a bug that could cause garbage to be inserted in the buffer when
changing character case in vi mode when using a multibyte locale.
q. Fixed a bug in the redisplay code that caused problems on systems
supporting multibyte characters when moving between history lines when the
new line has more glyphs but fewer bytes.
r. Undo and redo now work better after exiting vi insertion mode.
s. Make sure system calls are restarted after a SIGWINCH is received using
SA_RESTART.
t. Improvements to the code that displays possible completions when using
multibyte characters.
u. Fixed a problem when parsing nested if statements in inputrc files.
v. The completer now takes multibyte characters into account when looking for
quoted substrings on which to perform completion.
w. The history search functions now perform better bounds checking on the
history list.
3. New Features in Bash
a. ANSI string expansion now implements the \x{hexdigits} escape.
b. There is a new loadable `strftime' builtin.
c. New variable, COMP_WORDBREAKS, which controls the readline completer's
idea of word break characters.
d. The `type' builtin no longer reports on aliases unless alias expansion
will actually be performed.
e. HISTCONTROL is now a colon-separated list of values, which permits
more extensibility and backwards compatibility.
f. HISTCONTROL may now include the `erasedups' option, which causes all lines
matching a line being added to be removed from the history list.
g. `configure' has a new `--enable-multibyte' argument that permits multibyte
character support to be disabled even on systems that support it.
h. New variables to support the bash debugger: BASH_ARGC, BASH_ARGV,
BASH_SOURCE, BASH_LINENO, BASH_SUBSHELL, BASH_EXECUTION_STRING,
BASH_COMMAND
i. FUNCNAME has been changed to support the debugger: it's now an array
variable.
j. for, case, select, arithmetic commands now keep line number information
for the debugger.
k. There is a new `RETURN' trap executed when a function or sourced script
returns (not inherited child processes; inherited by command substitution
if function tracing is enabled and the debugger is active).
l. New invocation option: --debugger. Enables debugging and turns on new
`extdebug' shell option.
m. New `functrace' and `errtrace' options to `set -o' cause DEBUG and ERR
traps, respectively, to be inherited by shell functions. Equivalent to
`set -T' and `set -E' respectively. The `functrace' option also controls
whether or not the DEBUG trap is inherited by sourced scripts.
n. The DEBUG trap is run before binding the variable and running the action
list in a `for' command, binding the selection variable and running the
query in a `select' command, and before attempting a match in a `case'
command.
o. New `--enable-debugger' option to `configure' to compile in the debugger
support code.
p. `declare -F' now prints out extra line number and source file information
if the `extdebug' option is set.
q. If `extdebug' is enabled, a non-zero return value from a DEBUG trap causes
the next command to be skipped, and a return value of 2 while in a
function or sourced script forces a `return'.
r. New `caller' builtin to provide a call stack for the bash debugger.
s. The DEBUG trap is run just before the first command in a function body is
executed, for the debugger.
t. `for', `select', and `case' command heads are printed when `set -x' is
enabled.
u. There is a new {x..y} brace expansion, which is shorthand for {x.x+1,
x+2,...,y}. x and y can be integers or single characters; the sequence
may ascend or descend; the increment is always 1.
v. New ksh93-like ${!array[@]} expansion, expands to all the keys (indices)
of array.
w. New `force_fignore' shopt option; if enabled, suffixes specified by
FIGNORE cause words to be ignored when performing word completion even
if they're the only possibilities.
x. New `gnu_errfmt' shopt option; if enabled, error messages follow the `gnu
style' (filename:lineno:message) format.
y. New `-o bashdefault' option to complete and compgen; if set, causes the
whole set of bash completions to be performed if the compspec doesn't
result in a match.
z. New `-o plusdirs' option to complete and compgen; if set, causes directory
name completion to be performed and the results added to the rest of the
possible completions.
aa. `kill' is available as a builtin even when the shell is built without
job control.
bb. New HISTTIMEFORMAT variable; value is a format string to pass to
strftime(3). If set and not null, the `history' builtin prints out
timestamp information according to the specified format when displaying
history entries. If set, bash tells the history library to write out
timestamp information when the history file is written.
cc. The [[ ... ]] command has a new binary `=~' operator that performs
extended regular expression (egrep-like) matching.
dd. `configure' has a new `--enable-cond-regexp' option (enabled by default)
to enable the =~ operator and regexp matching in [[ ... ]].
ee. Subexpressions matched by the =~ operator are placed in the new
BASH_REMATCH array variable.
ff. New `failglob' option that causes an expansion error when pathname
expansion fails to produce a match.
gg. New `set -o pipefail' option that causes a pipeline to return a failure
status if any of the processes in the pipeline fail, not just the last
one.
4. New Features in Readline
a. History expansion has a new `a' modifier equivalent to the `g' modifier
for compatibility with the BSD csh.
b. History expansion has a new `G' modifier equivalent to the BSD csh `g'
modifier, which performs a substitution once per word.
c. All non-incremental search operations may now undo the operation of
replacing the current line with the history line.
d. The text inserted by an `a' command in vi mode can be reinserted with
`.'.
e. New bindable variable, `show-all-if-unmodified'. If set, the readline
completer will list possible completions immediately if there is more
than one completion and partial completion cannot be performed.
f. There is a new application-callable `free_history_entry()' function.
g. History list entries now contain timestamp information; the history file
functions know how to read and write timestamp information associated
with each entry.
h. Four new key binding functions have been added:
rl_bind_key_if_unbound()
rl_bind_key_if_unbound_in_map()
rl_bind_keyseq_if_unbound()
rl_bind_keyseq_if_unbound_in_map()
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.05b-release,
and the previous version, bash-2.05b-beta2.
1. Changes to Bash
a. Fixed an off-by-one error in the function that translates job
specifications.
b. Note that we're running under Emacs and disable line editing if
$EMACS == `t'.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.05b-beta2,
and the previous version, bash-2.05b-beta1.
1. Changes to Bash
a. Fixed the /= and %= arithmetic operators to catch division by zero.
b. Added putenv, setenv, unsetenv to getenv replacement for completeness.
c. Fixed a bug that could cause the -O expand_aliases invocation option
to not take effect.
d. Fixed a problem with process substitution that resulted in incorrect
behavior when the number of process substitutions in an individual
command approached 64.
2. Changes to Readline
a. Fixed a problem with backward-char-search when on a system with support
for multibyte characters when running in a locale without any multibyte
characters.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.05b-beta1,
and the previous version, bash-2.05b-alpha1.
1. Changes to Bash
a. Fixed a problem when parsing a POSIX.2 character class name while
evaluating a bracket expression containing multibyte characters.
b. Changed the help text for `bind' to make it clear that any command
that may be placed in ~/.inputrc is a valid argument to `bind'.
c. Added `help' builtin entries for `((', `[[', and arithmetic for.
d. malloc updated again:
o slightly better overflow and underflow detection by putting the
chunk size at the beginning and end of the chunk and making
sure they match in free/realloc
o partial page allocated to make things page-aligned no longer
completely wasted
o block coalescing now enabled by default
o splitting and coalescing enabled for 32-byte chunks, the most
common size requested
o fixed a problem that resulted in spurious underflow messages and
aborts
o bin sizes are precomputed and stored in an array rather than
being computed at run time
o malloc will return memory blocks back to the system if the block
being freed is at the top of the heap and of sufficient size to
make it worthwhile
o malloc/free/realloc now inline memset instead of calling the
libc function; uses Duff's device for good performance
e. Check for getservent(); make the service name completion code dependent
on its presence.
f. Changed the readline callback that executes a command bound to a key
sequence to not save the executed command on the history list and to
save and restore the parsing state.
g. Changes to lib/sh/snprintf.c: fixed some bugs in the `g' and `G'
floating point format display; implemented the "'" flag character
that turns on thousands' grouping; fixed behavior on systems where
MB_CUR_MAX does not evaluate to a constant.
h. The `unset' builtin no longer returns a failure status when asked to
unset a previously-unset variable or function.
i. Changes to the build system to make it easier to cross-compile bash
for different systems.
j. Added `,' to the characters that are backslash-escaped during filename
completion, to avoid problems with complete-into-braces and RCS filenames
containing commas.
k. Some changes to the multibyte character support code to avoid many calls
to strlen().
l. Bash now correctly honors setting LANG to some value when LC_ALL does not
already have a value.
m. Fixed a bug that could cause SIGSEGV when processing nested traps with
trap handlers.
n. The `source/.' builtin now restores the positional parameters when it
returns unless they were changed using the `set' builtin during the file's
execution.
o. Fixed a bug that caused a syntax error when a command was terminated by
EOF.
2. New Features in Bash
a. There is now support for placing the long help text into separate files
installed into ${datadir}/bash. Not enabled by default; can be turned
on with `--enable-separate-helpfiles' option to configure.
b. All builtins that take operands accept a `--' pseudo-option, except
`echo'.
c. The `echo' builtin now accepts \0xxx (zero to three octal digits following
the `0') in addition to \xxx (one to three octal digits) for SUSv3/XPG6/
POSIX.1-2001 compliance.
3. Changes to Readline
a. Fixed a small problem in _rl_insert_char with multibyte characters.
b. Fixes from IBM for line wrapping problems when using multibyte characters.
c. Fixed a problem which caused the display to be messed up when the last
line of a multi-line prompt (possibly containing invisible characters)
was longer than the screen width.
d. Fixed a problem with the vi-mode `r' command that ocurred on systems with
support for multibyte characters when running in a locale without any
multibyte characters.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.05b-alpha1,
and the previous version, bash-2.05a-release.
1. Changes to Bash
a. Some changes to work around inlining differences between compilers.
b. Added more prototypes for internal shell typedefs, to catch argument
passing errors when using pointers to functions.
c. The `cd' builtin now fails in posix mode when a valid directory cannot be
constructed from a relative pathname argument and the $PWD using pathname
canonicalization, and the -P option has not been supplied. Previously,
the shell would attempt to use what the user typed, leading to weird
values for $PWD and discrepancies between the value of $PWD and the
actual working directory.
d. The `cd' builtin now resets $PWD when canonicalization fails but a chdir
to the pathname passed as an argument succeeds (when not in posix mode).
e. The `fc' builtin has been fixed, as POSIX requires, to use the closest
history position in range when given an out-of-range argument.
f. The history file loading code was changed to allow lines to be saved in
the history list from the shell startup files.
g. `history -s args' now works better in compound commands.
h. The tilde expansion code was fixed to better recognize when it's being
invoked in an assignment context, which enables expansion after `='
and `:'.
i. Fixed the command name completion code so a slash is no longer appended
to a single match if there happens to be a directory with that name in
$PWD.
j. Fixed compound array assignment to no longer perform alias expansion, to
allow reserved words as array members, and to not produce extra output
when the `-v' option had been enabled.
k. Fixed the programmable completion code to better handle newlines in lists
of possible completions (e.g., `complete -W').
l. Removed the reserved words from the `bash-builtins' manual page.
m. Parser error reporting now attempts to do a better job of identifying the
token in error rather than doing straight textual analysis.
n. Fixes for Inf/NaN, locales, wide/multibyte characters and zero-length
arguments in the library snprintf(3) replacement.
o. `read -e' no longer does command name completion on the first word on
the line being read.
p. `select' now returns failure if the read of the user's selection fails.
q. Fixed a bug that could cause a core dump when setting $PIPESTATUS.
r. Fixes to not allocate so many job slots when the shell is running a loop
with job control enabled in a subshell of an interactive shell.
s. Fixed a bug in the trap code that caused traps to be inherited by
command substitutions in some cases.
t. Fixed a bug that could cause alias expansion to inappropriately expand
the word following the alias.
u. Fixed a bug in the `kill' builtin that mishandled negative pid arguments.
v. The parser is less lenient when parsing assignment statements where the
characters before the `=' don't comprise a valid identifier.
w. The arithmetic expression evaluation code now honors the setting of the
`-u' option when expanding variable names.
x. Fixed the arithmetic evaluation code to allow array subscripts to be
assigned (`let b[7]=42') and auto-incremented and auto-decremented
(e.g., b[7]++).
y. Reimplemented the existing prompt string date and time expansions using
strftime(3), which changed the output of \@ in some locales.
z. Fixed a bug that could cause a core dump when a special shell variable
(like RANDOM) was converted to an array with a variable assignment.
aa. Fixed a bug that would reset the handler for a signal the user had
trapped to a function that would exit the shell when setting the exit
trap in a non-interactive shell.
bb. Changed the execve(2) wrapper code to check whether or not a failing
command is a directory before looking at whether a `#!' interpreter
failed for some reason.
cc. Fixed a bug in the command printing code so it no longer inserts a `;'
after a newline, which produces a syntax error when reused as input.
dd. The code that expands $PS4 no longer inherits the `-x' flag.
ee. The bash-specific completion functions may now take advantage of the
double-TAB and M-? features of the standard readline completion
functions.
ff. The mail checking code no longer prints a message if the checked file's
size has not increased, even if the access time is less than the modification time.
gg. Rewrote the variable symbol table code: there is now a stack of
contexts, each possibly including a separate symbol table; there can
be more than one temporary environment supplied to nested invocations
of `./source'; the temporary environments no longer require so much
special-case code; shell functions now handle the temporary environment
and local variables more consistently; function scope exit is faster now
that the entire symbol table does not have to be traversed to dispose of
local variables; it is now easier to push vars from the temporary
environment to the shell's variable table in posix mode; some duplicated
code has been removed.
hh. Regularized the error message printing code; builtin_error is now called
more consistently, and common error message strings are handled by small
functions. This should make eventual message translation easier.
ii. Error messages now include the line number in a script when the shell
is not interactive.
jj. Array subscript expansion now takes place even when the array variable is
unset, so side effects will take place.
kk. Fixed a bug in the SICGHLD child-reaping code so that it won't find
jobs already marked as terminated if the OS reuses pids quickly enough.
ll. Fixed a bug that could cause a signal to not interrupt the `wait'
builtin while it was waiting for a background process to terminate.
mm. A couple of changes to make it easier for multiple shells to share history
files using `history -n', `history -r', and `history -w'.
nn. The `getopts' builtin always increments OPTIND to point to the next
option to be handled when an option is returned, whether it's valid
or not, as POSIX 1003.x-2001 requires.
oo. Changed some parts of the expansion code to avoid allocating and
immediately freeing memory without using the results for anything.
pp. The shell now keeps track of $IFS internally, updating its internal map
each time the variable is assigned a new value (or at local scope exit).
This saves thousands of hash lookups for IFS, which, while individually
cheap, add up.
qq. Rewrote the hash table code: searching and insertion are much faster now,
and it uses a better string hashing function; augmented the function
interface to simplify other parts of the code and remove duplicated code
rr. The shell now uses a simple, generic `object cache' for allocating and
caching words and word lists, which were the major users of
malloc/free.
ss. Fixed the assignment statement parsing code to allow whitespace and
newlines in subscripts when performing array element assignment.
tt. The shell now issues many fewer calls to sigprocmask and other signal
masking system calls.
uu. Fixed the `test' and conditional command file comparison operators to
work right when one file has a non-positive timestamp and the other
does not exist.
vv. Fixed some cases where the special characters '\001' and '\177' in the
values of variables or positional parameters caused incorrect expansion
results.
2. Changes to Readline
a. Fixed output of comment-begin character when listing variable values.
b. Added some default key bindings for common escape sequences produced by
HOME and END keys.
c. Fixed the mark handling code to be more emacs-compatible.
d. A bug was fixed in the code that prints possible completions to keep it
from printing empty strings in certain circumstances.
e. Change the key sequence printing code to print ESC as M\- if ESC is a
meta-prefix character -- it's easier for users to understand than \e.
f. Fixed unstifle_history() to return values that match the documentation.
g. Fixed the event loop (rl_event_hook) to handle the case where the input
file descriptor is invalidated.
h. Fixed the prompt display code to work better when the application has a
custom redisplay function.
i. Changes to make reading and writing the history file a little faster, and
to cope with huge history files without calling abort(3) from xmalloc.
j. The vi-mode `S' and `s' commands are now undone correctly.
3. New Features in Bash
a. If set, TMOUT is the default timeout for the `read' builtin.
b. `type' has two new options: `-f' suppresses shell function lookup, and
`-P' forces a $PATH search.
c. New code to handle multibyte characters.
d. `select' was changed to be more ksh-compatible, in that the menu is
reprinted each time through the loop only if REPLY is set to NULL.
The previous behavior is available as a compile-time option.
e. `complete -d' and `complete -o dirnames' now force a slash to be
appended to names which are symlinks to directories.
f. There is now a bindable edit-and-execute-command readline command,
like the vi-mode `v' command, bound to C-xC-e in emacs mode.
g. Added support for ksh93-like [:word:] character class in pattern matching.
h. The $'...' quoting construct now expands \cX to Control-X.
i. A new \D{...} prompt expansion; passes the `...' to strftime and inserts
the result into the expanded prompt.
j. The shell now performs arithmetic in the largest integer size the
machine supports (intmax_t), instead of long.
k. If a numeric argument is supplied to one of the bash globbing completion
functions, a `*' is appended to the word before expansion is attempted.
l. The bash globbing completion functions now allow completions to be listed
with double tabs or if `show-all-if-ambiguous' is set.
m. New `-o nospace' option for `complete' and `compgen' builtins; suppresses
readline's appending a space to the completed word.
n. New `here-string' redirection operator: <<< word.
o. When displaying variables, function attributes and definitions are shown
separately, allowing them to be re-used as input (attempting to re-use
the old output would result in syntax errors).
p. There is a new configuration option `--enable-mem-scramble', controls
bash malloc behavior of writing garbage characters into memory at
allocation and free time.
q. The `complete' and `compgen' builtins now have a new `-s/-A service'
option to complete on names from /etc/services.
r. `read' has a new `-u fd' option to read from a specified file descriptor.
s. Fix the completion code so that expansion errors in a directory name
don't cause a longjmp back to the command loop.
t. Fixed word completion inside command substitution to work a little more
intuitively.
u. The `printf' %q format specifier now uses $'...' quoting to print the
argument if it contains non-printing characters.
v. The `declare' and `typeset' builtins have a new `-t' option. When applied
to functions, it causes the DEBUG trap to be inherited by the named
function. Currently has no effect on variables.
w. The DEBUG trap is now run *before* simple commands, ((...)) commands,
[[...]] conditional commands, and for ((...)) loops.
x. The expansion of $LINENO inside a shell function is only relative to the
function start if the shell is interactive -- if the shell is running a
script, $LINENO expands to the line number in the script. This is as
POSIX-2001 requires.
y. The bash debugger in examples/bashdb has been modified to work with the
new DEBUG trap semantics, the command set has been made more gdb-like,
and the changes to $LINENO make debugging functions work better. Code
from Gary Vaughan.
z. New [n]<&word- and [n]>&word- redirections from ksh93 -- move fds (dup
and close).
aa. There is a new `-l' invocation option, equivalent to `--login'.
bb. The `hash' builtin has a new `-l' option to list contents in a reusable
format, and a `-d' option to remove a name from the hash table.
4. New Features in Readline
a. Support for key `subsequences': allows, e.g., ESC and ESC-a to both
be bound to readline functions. Now the arrow keys may be used in vi
insert mode.
b. When listing completions, and the number of lines displayed is more than
the screen length, readline uses an internal pager to display the results.
This is controlled by the `page-completions' variable (default on).
c. New code to handle editing and displaying multibyte characters.
d. The behavior introduced in bash-2.05a of deciding whether or not to
append a slash to a completed name that is a symlink to a directory has
been made optional, controlled by the `mark-symlinked-directories'
variable (default is the 2.05a behavior).
e. The `insert-comment' command now acts as a toggle if given a numeric
argument: if the first characters on the line don't specify a
comment, insert one; if they do, delete the comment text
f. New application-settable completion variable:
rl_completion_mark_symlink_dirs, allows an application's completion
function to temporarily override the user's preference for appending
slashes to names which are symlinks to directories.
g. New function available to application completion functions:
rl_completion_mode, to tell how the completion function was invoked
and decide which argument to supply to rl_complete_internal (to list
completions, etc.).
h. Readline now has an overwrite mode, toggled by the `overwrite-mode'
bindable command, which could be bound to `Insert'.
i. New application-settable completion variable:
rl_completion_suppress_append, inhibits appending of
rl_completion_append_character to completed words.
j. New key bindings when reading an incremental search string: ^W yanks
the currently-matched word out of the current line into the search
string; ^Y yanks the rest of the current line into the search string,
DEL or ^H deletes characters from the search string.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.05a-release,
and the previous version, bash-2.05a-rc1.
1. Changes to Bash
a. Fixed the `printf' builtin so that the variable name supplied as an
argument to a %n conversion must be a valid shell identifier.
b. Improved the random number generator slightly.
c. Changes to configuration to not put -I/usr/include into $CFLAGS, since
it messes up some includes.
d. Corrected description of POSIXLY_CORRECT in man page and info manual.
e. Fixed a couple of cases of incorrect function prototypes that sneaked
through and caused compilation problems.
f. A few changes to avoid potential core dumps in the programmable completion
code.
g. Fixed a configure problem that could cause a non-existent file to show
up in LIBOBJS.
h. Fixed a configure problem that could cause siglist.o to not be built when
required.
i. Changes to the strtoimax and strtoumax replacement functions to work
around buggy compilers.
j. Fixed a problem with the snprintf replacement function that could
potentially cause a core dump.
2. Changes to Readline
a. Fixed a locale-specific problem in the vi-mode `goto mark' command.
b. Fixed Makefile to not put -I/usr/include into CFLAGS, since it can cause
include file problems.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.05a-rc1,
and the previous version, bash-2.05a-beta1.
1. Changes to Bash
a. Fixed the snprintf replacement to correctly implement the `alternate form'
of the %g and %G conversions.
b. Fixed snprintf to correctly handle the optional precision with the %g and
%G conversions.
c. Fixed the arithmetic evaluation code to correct the values of `@' and `_'
when translating base-64 constants (they were backwards).
d. New library functions for formatting long and long long ints.
e. Fixed a few places where negative array subscripts could have occurred,
mostly as the result of systems using signed characters.
f. Fixed a few places that assumed a pid_t was no wider than an int.
g. Fixed the `maildir' mail checking code to work on systems where a
`struct stat' doesn't include an `st_blocks' member.
h. Fixed snprintf to make `unsigned long long' conversion formats (%llu)
work better.
i. Fixed snprintf to not print a sign when asked to do an unsigned conversion.
j. Made configure changes to avoid compiling empty source files in lib/sh.
k. New replacement functions (if necessary) for strtoull, strtoll, strtoimax,
strtoumax.
l. The `printf' builtin now handles the `ll' and `j' length modifiers
directly, since they can affect the type and width of the argument
passed to printf(3).
m. Renamed a number of the bash-specific autoconf macros in aclocal.m4 to
have more sytematic naming, with accompanying changes to configure.in.
n. Fixed snprintf to handle long doubles and the %a/%A conversions by
falling back to sprintf, as long as sprintf supports them.
o. Fixed return value from vsnprintf/snprintf to be the number of characters
that would have been printed, even if that number exceeds the buffer
size passed as an argument.
p. Bash no longer attempts to define its own versions of some ctype macros
if they are implemented as functions in libc but not as macros in
.
q. Changed the variable printing code (used by `set', `export', etc.) to
not use the $'...' syntax when in posix mode, since that caused
interoperability problems with other shells (most notably with autoconf).
When not in posix mode, it uses $'...' if the string to be printed
contains non-printing characters and regular single quotes otherwise.
r. snprintf now recognizes the %F conversion.
s. Fixed a bug that could cause the wrong status to be returned by a shell
function when the shell is compiled without job control and a null
command containing a command substutition was executed in the function.
t. When in posix mode, the default value for MAILCHECK is 600.
u. Bash only initializes FUNCNAME, GROUPS, and DIRSTACK as special variables
if they're not in the initial environment.
v. If SECONDS appears in the initial environment with a valid integer value,
bash uses that as the starting value, as if an assignment had been
performed.
w. Bash no longer auto-exports HOME, PATH, SHELL, or TERM, even though it
gives them default values if they don't appear in the initial environment.
x. Bash no longer auto-exports HOSTNAME, HOSTTYPE, MACHTYPE, or OSTYPE,
even if it assigns them default values.
y. Bash no longer removes the export attribute from SSH_CLIENT or SSH2_CLIENT
if they appear in the initial environment.
z. Bash no longer attempts to discover if it's being run by sshd in order to
run the startup files. If the SSH_SOURCE_BASHRC is uncommented in
config-top.h it will attempt to do so as previously, but that's commented
out in the distributed version.
aa. Fixed a typo in the code that tests for LC_NUMERIC.
bb. The POSIXLY_CORRECT shell variable and its effects are now documented.
cc. Some changes to several of the support shell scripts included in the
definitions to try to avoid race conditions and attacks.
dd. Several changes to avoid warnings from `gcc -Wall'.
ee. Fixed a problem with the `unset' builtin that could cause incorrect
results if asked to unset a variable and an array subscript in the
same command.
ff. A few changes to the shell's temporary file creation code to avoid
potential file descriptor leaks and to prefer the system's idea of
the temporary directory to use.
gg. Fixes to build with the C alloca in lib/malloc/alloca.c if the system
requires it but the shell has been configured --without-bash-malloc.
hh. Updated the documentation to note that only interactive shells resend
SIGHUP to all jobs before exiting.
ii. Fixes to only pass unquoted tilde words to tilde_expand, rather than
rely on tilde_expand or getpwnam(3) to handle the quotes (MacOS 10.x
will remove backslashes in any login name passed to getpwnam(3)).
jj. Small change from Paul Eggert to make LINENO right in commands run with
`bash -c'.
2. New Features in Bash
a. The `printf' builtin now handles the %a and %A conversions if they're
implemented by printf(3).
b. The `printf' builtin now handles the %F conversion (just about like %f).
c. The `printf' builtin now handles the %n conversion like printf(3). The
corresponding argument is the name of a shell variable to which the
value is assigned.
3. Changes to Readline
a. Fixed a few places where negative array subscripts could have occurred.
b. Fixed the vi-mode code to use a better method to determine the bounds of
the array used to hold the marks.
c. Fixed the defines in chardefs.h to work better when chars are signed.
d. Fixed configure.in to use the new names for bash autoconf macros.
e. Readline no longer attempts to define its own versions of some ctype
macros if they are implemented as functions in libc but not as macros in
.
f. Fixed a problem where rl_backward could possibly set point to before
the beginning of the line.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.05a-beta1,
and the previous version, bash-2.05a-alpha1.
1. Changes to Bash
a. Fixed a bug in the evalution of arithmetic `for' statements when the
expanded expression is NULL.
b. Fixed an unassigned variable problem in the redirection printing code.
c. Added more prototypes to extern function declarations in the header
files and to static function declarations in C source files.
d. Make sure called functions have a prototype in scope, to get the arguments
and return values right instead of casting. Removed extern function
declarations from C source files that were already included in header
files.
e. Changed some function arguments to use function typedefs in general.h so
the prototypes can be checked. The only use of Function and VFunction
now is for unwind-protects.
f. More const changes to function arguments and appropriate variables.
g. Changed the mail checking support to handle `maildir'-style mail
directories.
h. Augmented the bash malloc to pass in the file and line number information
for each malloc, realloc, and free. This should result in better error
messages.
i. The `old' gnu malloc is no longer a configuration option.
j. Augmented the bash malloc with optional tracing and registering allocated
and freed memory.
k. Prompt string decoding now saves and restores the value of $? when it
expands the prompt string, so command substitutions don't change $?.
i. Array indices are now `long', since shell arithmetic is performed as long,
and the internal arrayind_t type is used consistently.
j. Some more `unsigned char *' fixes from Paul Eggert.
k. Fixed a bad call to builtin_error that could cause core dumps when making
local variables.
l. `return' may no longer be used to terminate a `select' command, for
compatibility with ksh.
m. Changed code that reads octal numbers to do a better job of detecting
overflows.
n. The time formatting code no longer uses absolute indices into a buffer,
because the buffer size changes depending on the size of a `time_t'.
o. `umask' now prints four digits when printing in octal mode, for
compatibility with other shells.
p. Lots of changes to the `printf' builtin from Paul Eggert: it handles `L'
formats and long doubles better, and internal functions have been
simpified where appropriate.
q. Some `time_t' fixes for machines were a time_t is bigger than a long.
r. Replaced some bash-specific autoconf macros with standard equivalents.
s. Improvmed the code that constructs temporary filenames to make the
generated names a bit more random.
t. Added code that checks for ascii before calling any of the is* ctype
functions.
u. Changed some places where a `char' was used as an array subscript to use
`unsigned char', since a `char' can be negative if it's signed by default.
v. Lots of changes to the `ulimit' builtin from Paul Eggert to add support
for the new POSIX-200x RLIM_SAVED_CUR and RLIM_SAVED_MAX values and
simplify the code.
w. `ulimit' now prints the description of a resource in any error message
relating to fetching or setting that resource's limits.
x. The `snprintf' replacement now computes maximum values at compile
time rather than using huge constants for things like long long.
y. Interactive shells now ignore `set -n'.
z. Changed the malloc bookkeeping information so that it's now 8 bytes
instead of 12 on most 32-bit machines (saving 4 bytes per allocation),
restoring 8-byte alignment.
aa. The malloc error reporting code now attempts to print the file and line
number of the call that caused the error.
bb. Changed the redirection error reporting code to catch EBADF errors and
report the file descriptor number rather than the file being redirected
to or from (e.g., things like `exec 4242&word' redirection now works in POSIX mode as it does by default,
since POSIX.2 leaves it unspecified.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.05-beta2,
and the previous version, bash-2.05-beta1.
1. Changes to Bash
a. Fixed a bug in the arithmetic evaluation code so that a^=b is supported.
b. Fixed startup so posixly_correct is retained across subshells begun to
execute scripts without a leading `#!'.
c. Fixed a bug that caused $(< file) to not work in a (...) subshell.
d. Added config support for Linux running on the IBM S390.
e. Fixed a bug that caused bash to get its input pointer out of sync when
reading commands through a pipe and running a command with standard
input redirected from a file.
f. Made a change so that command completion now makes about half as many
stat(2) calls when searching the $PATH.
g. Fixed a bug that caused variable assignments preceding `return' to not
be propagated to the shell environment in POSIX mode.
h. Fixed a bug with ${parameter[:]?word} -- tilde expansion was not performed
on `word'.
i. In POSIX mode, `break' and `continue' do not complain and return success
if called when the shell is not executing a loop.
j. Fixed `bash -o posix' to work the same as `bash --posix'.
k. Fixed a bug where variable assignments preceding `eval' or `source/.'
would not show up in the environment exported to subshells run by the
commands.
l. In POSIX mode, shells started to execute command substitutions inherit
the value of the `-e' option from their parent shell.
m. In POSIX mode, aliases are expanded even in non-interactive shells.
n. Changed some of the job control messages to display the text required by
POSIX.2 when the shell is in POSIX mode.
o. Fixed a bug in `test' that caused it to occasionally return incorrect
results when non-numeric arguments were supplied to `-t'.
2. Changes to Readline
a. Some changes were made to avoid gcc warnings with -Wall.
b. rl_get_keymap_by_name now finds keymaps case-insensitively, so
`set keymap EMACS' works.
c. The history file writing and truncation functions now return a useful
status on error.
d. Fixed a bug that could cause applications to dereference a NULL pointer
if a NULL second argument was passed to history_expand().
3. New Features in Bash
a. doc/readline.3 has been moved to the readline distribution.
4. New Features in Readline
a. New function, rl_get_screen_size (int *rows, int *columns), returns
readline's idea of the screen dimensions.
b. The timeout in rl_gather_tyi (readline keyboard input polling function)
is now settable via a function (rl_set_keyboard_input_timeout()).
c. Renamed the max_input_history variable to history_max_entries; the old
variable is maintained for backwards compatibility.
d. The list of characters that separate words for the history tokenizer is
now settable with a variable: history_word_delimiters. The default
value is as before.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.05-beta1,
and the previous version, bash-2.05-alpha1.
1. Changes to Bash
a. Changes to allow shared library and object building on the GNU Hurd.
b. Fixes to the way exported functions are placed into the environment and
cached.
c. The globbing library once again respects locales when processing ranges
in bracket expressions while doing pattern matching.
d. System-specific configuration changes for: Tru 64, Interix
e. Bashbug now uses /usr/bin/editor as one of the editing alternatives, and
will use mktemp(1) or tempfile(1), if present, for temporary file creation.
f. Bash no longer performs a binary file check on a script argument that's
really a tty (like /dev/fd/0 or /dev/stdin).
g. Fixed a bug in the execution of shell scripts that caused the effects of
$BASH_ENV to be undone in some cases.
h. Fixed several bugs that made `bash [-i] /dev/stdin' not work correctly.
i. Several changes to the job control code to avoid some signal state
manipulation.
j. The Bash malloc no longer blocks signals as often, which should make it
faster.
k. Fixed a parsing bug that did not allow backslash to escape a single quote
inside a $'...' construct.
l. Fixed a bug that caused things like ${var:=$'value'} to be parsed
incorrectly. This showed up in newer versions of autoconf.
m. Fixed a bug in the bash-specific readline initialization that caused
key bindings to bash-specific function names appearing in .inputrc to
not be honored.
n. Bash now sets the file descriptor it uses to save the file descriptor
opened on a shell script to close on exec.
o. Fixed a bug in the prompt string decoding that caused it to misbehave
when presented an octal sequence of fewer than three characters.
p. Fixed the `test' builtin to return an error if `[' is supplied a single
argument that is not `]'.
q. Fixed a bug that caused subshells started to run executable shell scripts
without a leading `#!' to incorrectly inherit an argument list preceding
a shell builtin (like such a script called from a script sourced with `.',
where there were variable assignments preceding the `.' command)
r. Fixed a bug that caused changes to variables supplied in an assignment
statement preceding a shell builtin to not be honored (like a script
run with `.').
s. HOSTTYPE, OSTYPE, and MACHTYPE are set only if they do not have values
when the shell is started.
t. Fixed a bug that caused SIGINT to kill shell scripts after the script
called `wait'.
u. The `fc' builtin now tries to create its temporary files in the directory
named by $TMPDIR.
v. Bash no longer calls any Readline functions or uses any Readline variables
not declared in readline.h.
w. Fixed a bug that caused some substitutions involving $@ to not be split
correctly, especially expansions of the form ${paramterOPword}.
x. SSH2_CLIENT is now treated like SSH_CLIENT and not auto-exported if it
appears in the initial environment.
y. Fixed a couple of problems with shell scripts without a leading `#!'
being executed out of shell functions that could cause core dumps if
such a script attempted to execute `return'.
z. Fixed a problem with the `-nt' and `-ot' binary operators for the
`test/[' builtin and the `[[' conditional command that caused wrong
return values if one of the file arguments did not exist.
aa. Fixed a bug that caused non-interactive shells which had previously
executed `shopt -s expand_aliases' to fail to expand aliases in a
command like `(command) &'.
2. Changes to Readline
a. Changes to make most (but not yet all -- there is still crlf()) of the
exported readline functions declared in readline.h have an rl_ prefix.
b. More `const' changes in function arguments, mostly for completion
functions.
c. Fixed a bug in rl_forward that could cause the point to be set to before
the beginning of the line in vi mode.
d. Fixed a bug in the callback read-char interface to make it work when a
readline function pushes some input onto the input stream with
rl_execute_next (like the incremental search functions).
e. Fixed a file descriptor leak in the history file manipulation code that
was tripped when attempting to truncate a non-regular file (like
/dev/null).
f. Some existing variables are now documented and part of the public
interface (declared in readline.h): rl_explict_arg, rl_numeric_arg,
rl_editing_mode, rl_last_func.
g. Renamed rltty_set_default_bindings to rl_tty_set_default_bindings and
crlf to rl_crlf, so there are no public functions declared in readline.h
without an `rl_' prefix. The old functions still exist for backwards
compatibility.
3. New Features in Bash
a. A new loadable builtin, realpath, which canonicalizes and expands symlinks
in pathname arguments.
b. When `set' is called without options, it prints function defintions in a
way that allows them to be reused as input. This affects `declare' and
`declare -p' as well.
4. New Features in Readline
a. New application-callable function rl_set_prompt(const char *prompt):
expands its prompt string argument and sets rl_prompt to the result.
b. New application-callable function rl_set_screen_size(int rows, int cols):
public method for applications to set readline's idea of the screen
dimensions.
c. The history example program (examples/histexamp.c) is now built as one
of the examples.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.05-alpha1,
and the previous version, bash-2.04-release.
1. Changes to Bash
a. A fix was made to allow newlines in compond array assignments.
b. configure now checks for real-time signals with unusable values.
c. Interactive shells no longer exit if a substitution fails because of an
unset variable within a sourced file.
d. Fixed a problem with incorrect matching of extended glob patterns when
doing pattern substitution.
e. `{' is now quoted by the completion code when it appears in a filename.
f. Fixed an error in pattern matching that caused the matcher to not
correctly skip the rest of a bracket expression after a character
matched.
g. Fixed a bug in the IFS word splitting code to make a non-whitespace IFS
character preceded by IFS whitespace part of the current delimiter rather
than generating a separate field.
h. The {!prefix@} expansion now generates separate words, analogous to $@,
when double-quoted.
i. Command substitution now ignores NUL bytes in the command output, and the
parser ignores them on input.
j. A fix was made to the job control code to prevent hanging processes when
the shell thinks background processes are running but the kernel returns
-1/ECHILD from waitpid().
k. `pwd' now prints an error message if the write fails when displaying the
current directory.
l. When in POSIX mode, the shell prints trap dispostions without a leading
`SIG' in the signal specification.
m. Fixed a parser bug that caused the current command's line count to be
messed up by a compound array assignment.
n. Fixed a bug in the unwind-protect code that caused bad behavior on machines
where ints and pointers are not the same size.
o. System-specific configure changes for: MacOS X.
p. Changes for Cygwin to translate \r\n and \r to \n and to set file
descriptors used for reading input to text mode in various places.
q. Fixed a bug that caused `!' to occasionally not be honored when in
a (...) subshell.
r. Bash no longer assumes that getcwd() will return any useful error message
in the buffer passed as an argument if the call fails.
s. The `source', `.', and `fc' builtins no longer check whether a file is
binary before reading commands from it.
t. Subshells no longer turn off job control when they exit, since that
sometimes resulted in the terminal being reset to the wrong process
group.
u. The history code no longer tries to save the second and subsequent lines
of a multi-line command if the first line was not saved.
v. The history saving code now does a better job of saving blank lines in a
multi-line command.
w. Removed a `feature' that made `ulimit' silently translate `unlimited' to
the current hard limit, which obscured some kernel error returns.
x. Fixed the grammar so that `}' is recognized as a reserved word after
another reserved word, rather than requiring a `;' or newline. This
means that constructs like
{ { echo a b c ; } }
work as expected.
y. Conditional commands ([[...]]) now perform tilde expansion on their
arguments.
z. Noted in the documentation that `set -a' will cause functions to be
exported if they are defined after `set -a' is executed.
aa. When an interactive login shell starts, if $PWD and $HOME refer to the
same directory but are not the same string, $PWD is set to $HOME.
bb. Fixed `printf' to handle invalid floating point numbers better.
cc. Temporary files are now created with random filenames, to improve security.
dd. The readline initialization code now binds the custom bash functions and
key bindings after the readline defaults are set up.
ee. Fixed the `source' builtin to no longer overwrite a shell function's
argument list, even if the sourced file changes the positional parameters.
ff. A bug fix was made in the expansion of `$*' in contexts where it should
not be split, like assignment statements.
gg. Fixed a bug in the parameter substring expansion to handle conditional
arithmetic expressions ( exp ? val1 : val2 ) without cutting the expression
off at the wrong `:'.
hh. The `<>' redirection is no longer subject to the current setting of
`noclobber', as POSIX.2 specifies.
ii. Fixed a bug in the conditional command parsing code that caused expressions
in parentheses to occasionally be parsed incorrectly.
jj. Fixed a bug in the ((...)) arithmetic command to allow do...done or
{...} to follow the )) without an intervening list terminator.
kk. `printf' now treats `\E' the same as `\e' when performing backslash escape
expansion for the `%b' format specifier.
ll. When in POSIX mode, the shell no longer searches the current directory for
a file to be sourced with `.' or `source' if `.' is not in $PATH.
mm. Interactive comments are no longer turned off when POSIX mode is disabled.
nn. The UID, EUID, HOSTNAME variables are not set if they are in the shell's
environment when it starts up.
oo. Fixed a bug in the `command' builtin so the effect of a command like
`command exec 4(...)
expansions to defer removal until after any current shell function has
finished executing.
f. Fixed a bug in `select' which caused it to not handle the `continue'
builtin correctly.
g. Autoconf tests added for cygwin32 and mingw32.
2. New Features in Bash
a. The `--with-bash-malloc' configure option replaces `--with-gnu-malloc'
(which is still there for backwards compatibility).
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.04-beta1,
and the previous version, bash-2.04-alpha1.
1. Changes to Bash
a. Fixed a bug in the programmable completion code that occurred when
trying to complete command lines containing a `;' or `@'.
b. The file descriptor from which the shell is reading a script is now
moved to a file descriptor above the user-addressible range.
c. Changes to `printf' so that it can handle integers beginning with 0
or 0x as octal and hex, respectively.
d. Fixes to the programmable completion code so it handles nonsense like
`compgen -C xyz' gracefully.
e. The shell no longer modifies the signal handler for SIGPROF, allowing
profiling again on certain systems.
f. The shell checks for a new window size, if the user has requested it,
after a process exits due to a signal.
g. Fixed a bug with variables with null values in a program's temporary
environment and the bash getenv() replacement.
h. `declare' and the other builtins that take variable assignments as
arguments now honor `set -a' and mark modified variables for export.
i. Some changes were made for --dump-po-strings mode when writing strings
with embedded newlines.
j. The code that caches export strings from the initial environment now
duplicates the string rather than just pointing into the environment.
k. The filename completion quoting code now uses single quotes by default
if the filename being completed contains newlines, since \
has a special meaning to the parser.
l. Bash now uses typedefs bits32_t and u_bits32_t instead of int32_t and
u_int32_t, respectively to avoid conflicts on certain Unix versions.
m. Configuration changes were made for: Rhapsody, Mac OS, FreeBSD-3.x.
n. Fixed a problem with hostname-to-ip-address translation in the
/dev/(tcp|udp)/hostname/port redirection code.
o. The texinfo manual has been reorganized slightly.
p. Filename generation (globbing) range comparisons in bracket expressions
no longer use strcoll(3) even if it is available, since it has unwanted
effects in certain locales.
q. Fixed a cosmetic problem in the source that caused the shell to not
compile if DPAREN_ARITHMETIC was not defined but ARITH_FOR_COMMAND was.
r. Fixed a bug in the here-document code tripped when the file descriptor
opened to the file containing the text of the here document was the
same as a redirector specified by the user.
s. Fixed a bug where the INVERT_RETURN flag was not being set for `pipeline'
in `time ! pipeline'.
t. Fixed a bug with the `wait' builtin which manifested itself when an
interrupt was received while the shell was waiting for asynchronous
processes in a shell script.
u. Fixed the DEBUG trap code so that it has the correct value of $?.
v. Fixed a bug in the parameter pattern substitution code that could cause
the shell to attempt to free unallocated memory if the pattern started
with `/' and an expansion error occurs.
w. Fixed a bug in the positional parameter substring code that could
cause the shell to loop freeing freed memory.
x. Fixed a bug in the positional parameter pattern substitution code so
that it correctly handles null replacement strings with a pattern
string prefixed with `%' or `#'.
y. The shell no longer attempts to import functions from the environment if
started with `-n'.
z. Fixed a bug that caused `return' in a command substitution executed in
a shell function to return from the function in a subshell and continue
execution.
aa. `hash -p /pathname/with/slashes name' is no longer allowed when the shell
is restricted.
bb. The wait* job control functions now behave better if called when there
are no unwaited-for children.
cc. Command substitution no longer unconditionally disables job control in
the subshell started to run the command.
dd. A bug was fixed that occasionally caused traps to mess up the parser
state.
ee. `bashbug' now honors user headers in the mail message it sends.
ff. A bug was fixed that caused the `:p' history modifier to not print the
history expansion if the `histverify' option was set.
2. Changes to Readline
a. Fixed a bug in the redisplay code for lines with more than 256 line
breaks.
b. A bug was fixed which caused invisible character markers to not be
stripped from the prompt string if the terminal was in no-echo mode.
c. Readline no longer tries to get the variables it needs for redisplay
from the termcap entry if the calling application has specified its
own redisplay function. Readline treats the terminal as `dumb' in
this case.
d. Fixes to the SIGWINCH code so that a multiple-line prompt with escape
sequences is redrawn correctly.
3. New Features in Bash
a. `bashbug' now accepts `--help' and `--version' options.
b. There is a new `xpg_echo' option to `shopt' that controls the behavior
of echo with respect to backslash-escaped characters at runtime.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.04-alpha1,
and the previous version, bash-2.04-devel.
1. Changes to Bash
a. Fixed a bug that could cause core dumps when performing substring
expansion.
b. Shared object configuration changes for: Solaris, OSF/1
c. The POSIX_GLOB_LIBRARY code that uses the POSIX.2 globbing facilities
for pathname expansion now understands GLOBIGNORE.
d. The code that implements `eval' was changed to save the value of the
current prompt, so an eval in a shell function called by the programmable
completion code will not change the prompt to $PS2.
e. Restored the undocumented NON_INTERACTIVE_LOGIN_SHELLS #define to
config-top.h. If this is defined, all login shells will read the
startup files, not just interactive and non-interactive started with
the `--login' option.
f. Fixed a bug that caused the expansion code to occasionally dump core if
IFS contained characters > 128.
g. Fixed a problem with the grammar so that a newline is not required
after the `))' in the new-style arithmetic for statement; a semicolon
may be used as expected.
h. Variable indirection may now reference the shell's special variables.
i. The $'...' and $"..." constructs are now added to the history correctly
if they contain newlines and command-oriented history is enabled.
j. It is now an error to try to assign a value to a function-local copy
of a readonly shell variable (declared with the `local' builtin).
2. Changes to Readline
a. The history file code now uses O_BINARY mode when reading and writing
the history file on cygwin32.
3. New Features in Bash
a. A new programmable completion facility, with two new builtin commands:
complete and compgen.
b. configure has a new option, `--enable-progcomp', to compile in the
programmable completion features (enabled by default).
c. `shopt' has a new option, `progcomp', to enable and disable programmable
completion at runtime.
d. Unsetting HOSTFILE now clears the list of hostnames used for completion.
4. New Features in Readline
a. A new variable, rl_gnu_readline_p, always 1. The intent is that an
application can verify whether or not it is linked with the `real'
readline library or some substitute.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.04-devel,
and the previous version, bash-2.03-release.
1. Changes to Bash
a. System-specific configuration and source changes for: Interix, Rhapsody
b. Fixed a bug in execute_cmd.c that resulted in a compile-time error if
JOB_CONTROL was not defined.
c. An obscure race condition in the trap code was fixed.
d. The string resulting from $'...' is now requoted to avoid any further
expansion.
e. The $'...' quoting syntax now allows backslash to escape a single quote,
for ksh-93 compatibility.
f. The $"..." quoting syntax now escapes backslashes and double quotes in
the translated string when displaying them with the --dump-po-strings
option.
g. `echo -e' no longer converts \' to '.
h. Fixes were made to the extended globbing code to handle embedded (...)
patterns better.
i. Some improvements were made to the code that unsets `nodelay' mode on
the file descriptor from which bash is reading input.
j. Some changes were made to the replacement termcap library for better
operation on MS-DOS.
k. Some changes were made to the tilde expansion code to handle backslash
as a pathname separator on MS-DOS.
l. The source has been reorganized a little bit -- there is now an `include'
subdirectory, and lib/posixheaders has been removed.
m. Improvements were made to the `read' builtin so that it makes many
fewer read(2) system calls.
n. The expansion of $- will include `c' and `s' when those options are
supplied at shell invocation.
o. Several improvments were made to the completion code: variable completion
now works better when there are unterminated expansions, command
completion understands quotes better, and completion now works in certain
unclosed $(... constructs.
p. The arithmetic expansion code was fixed to not need the value of a
variable being assigned a value (fixes the "ss=09; let ss=10" bug).
q. Some changes were made to make exported environment creation faster.
r. The html documentation will be installed into $(htmldir) if that variable
has a value when `make install' is run.
s. Fixed a bug that would cause the bashrc file to be sourced inappropriately
when bash is started by sshd.
t. The SSH_CLIENT environment variable is no longer auto-exported.
u. A bug that caused redirections with (...) subshells to be performed in
the wrong order was fixed.
v. A bug that occasionally caused inappropriate expansion of assignment
statements in compound array assignments was fixed.
w. The code that parses the words in a compound array assignment was
simplified considerably and should work better now.
x. Fixes to the non-job-control code in nojobs.c to make it POSIX.2-compliant
when a user attempts to retrieve the status of a terminated background
process.
y. Fixes to the `printf' builtin so that it doesn't try to expand all
backslash escape sequences in the format string before parsing it for
% format specifiers.
2. Changes to Readline
a. The history library tries to truncate the history file only if it is a
regular file.
b. A bug that caused _rl_dispatch to address negative array indices on
systems with signed chars was fixed.
c. rl-yank-nth-arg now leaves the history position the same as when it was
called.
d. Changes to the completion code to handle MS-DOS drive-letter:pathname
filenames.
e. Completion is now case-insensitive by default on MS-DOS.
f. Fixes to the history file manipulation code for MS-DOS.
g. Readline attempts to bind the arrow keys to appropriate defaults on MS-DOS.
h. Some fixes were made to the redisplay code for better operation on MS-DOS.
i. The quoted-insert code will now insert tty special chars like ^C.
j. A bug was fixed that caused the display code to reference memory before
the start of the prompt string.
k. More support for __EMX__ (OS/2).
l. A bug was fixed in readline's signal handling that could cause infinite
recursion in signal handlers.
m. A bug was fixed that caused the point to be less than zero when rl_forward
was given a very large numeric argument.
n. The vi-mode code now gets characters via the application-settable value
of rl_getc_function rather than calling rl_getc directly.
3. New Features in Bash
a. The history builtin has a `-d offset' option to delete the history entry
at position `offset'.
b. The prompt expansion code has two new escape sequences: \j, the number of
active jobs; and \l, the basename of the shell's tty device name.
c. The `bind' builtin has a new `-x' option to bind key sequences to shell
commands.
d. There is a new shell option, no_empty_command_completion, which, when
enabled, disables command completion when TAB is typed on an empty line.
e. The `help' builtin has a `-s' option to just print a builtin's usage
synopsys.
f. There are several new arithmetic operators: id++, id-- (variable
post-increment/decrement), ++id, --id (variabl pre-increment/decrement),
expr1 , expr2 (comma operator).
g. There is a new ksh-93 style arithmetic for command:
for ((expr1 ; expr2; expr3 )); do list; done
h. The `read' builtin has a number of new options:
-t timeout only wait timeout seconds for input
-n nchars only read nchars from input instead of a full line
-d delim read until delim rather than newline
-s don't echo input chars as they are read
i. The redirection code now handles several filenames specially:
/dev/fd/N, /dev/stdin, /dev/stdout, and /dev/stderr, whether or
not they are present in the file system.
j. The redirection code now recognizes pathnames of the form
/dev/tcp/host/port and /dev/udp/host/port, and tries to open a socket
of the appropriate type to the specified port on the specified host.
k. The ksh-93 ${!prefix*} expansion, which expands to the names of all
shell variables whose names start with prefix, has been implemented.
l. There is a new dynamic variable, FUNCNAME, which expands to the name of
a currently-executing function. Assignments to FUNCNAME have no effect.
m. The GROUPS variable is no longer readonly; assignments to it are silently
discarded. This means it can be unset.
4. New Features in Readline
a. Parentheses matching is now always compiled into readline, and enabled
or disabled when the value of the `blink-matching-paren' variable is
changed.
b. MS-DOS systems now use ~/_inputrc as the last-ditch inputrc filename.
c. MS-DOS systems now use ~/_history as the default history file.
d. history-search-{forward,backward} now leave the point at the end of the
line when the string to search for is empty, like
{reverse,forward}-search-history.
e. history-search-{forward,backward} now leave the last history line found
in the readline buffer if the second or subsequent search fails.
f. New function for use by applications: rl_on_new_line_with_prompt, used
when an application displays the prompt itself before calling readline().
g. New variable for use by applications: rl_already_prompted. An application
that displays the prompt itself before calling readline() must set this to
a non-zero value.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.03-release,
and the previous version, bash-2.03-beta2.
1. Changes to Bash
a. A file descriptor leak in the `fc' builtin was fixed.
b. A bug was fixed in the `read' builtin that caused occasional spurious
failures when using `read -e'.
c. The version code needed to use the value of the cpp variable
CONF_MACHTYPE rather than MACHTYPE.
d. A new test was added to exercise the command printing and copying code.
e. A bug was fixed that caused `time' to be recognized as a reserved word
if it was the first pattern in a `case' statement pattern list.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.03-beta2,
and the previous version, bash-2.03-beta1.
1. Changes to Bash
a. Slight additions to support/shobj-conf, mostly for the benefit of AIX 4.2.
b. config.{guess,sub} support added for the NEC SX4.
c. Changed some of the cross-compiling sections of the configure macros in
aclocal.m4 so that configure won't abort.
d. Slight changes to how the HTML versions of the bash and readline manuals
are generated.
e. Fixed conditional command printing to avoid interpreting printf `%'-escapes
in arguments to [[.
f. Don't include the bash malloc on all variants of the alpha processor.
g. Changes to configure to make --enable-profiling work on Solaris 2.x.
h. Fixed a bug that manifested itself when shell functions were called
between calls to `getopts'.
i. Fixed pattern substitution so that a bare `#'as a pattern causes the
replacement string to be prefixed to the search string, and a bare
`%' causes the replacement string to be appended to the search string.
j. Fixed a bug in the command execution code that caused child processes
to occasionally have the wrong value for $!.
2. Changes to Readline
a. Added code to the history library to catch history substitutions using
`&' without a previous history substitution or search having been
performed.
3. New Features in Bash
4. New Features in Readline
a. New bindable variable: `isearch-terminators'.
b. New bindable function: `forward-backward-delete-char' (unbound by default).
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.03-beta1,
and the previous version, bash-2.03-alpha.
1. Changes to Bash
a. A change was made to the help text for `{...}' to make it clear that a
semicolon is required before the closing brace.
b. A fix was made to the `test' builtin so that syntax errors cause test
to return an exit status > 1.
c. Globbing is no longer performed on assignment statements that appear as
arguments to `assignment builtins' such as `export'.
d. System-specific configuration changes were made for: Rhapsody,
AIX 4.2/gcc, BSD/OS 4.0.
e. New loadable builtins: ln, unlink.
f. Some fixes were made to the globbing code to handle extended glob patterns
which immediately follow a `*'.
g. A fix was made to the command printing code to ensure that redirections
following compound commands have a space separating them from the rest
of the command.
h. The pathname canonicalization code was changed to produce fewer leading
`//' sequences, since those are interpreted as network file system
pathnames on some systems.
i. A fix was made so that loops containing `eval' commands in commands passed
to `bash -c' would not exit prematurely.
j. Some changes were made to the job reaping code when the shell is not
interactive, so the shell will retain exit statuses longer for examination
by `wait'.
k. A fix was made so that `jobs | command' works again.
l. The erroneous compound array assignment var=((...)) is now a syntax error.
m. A change was made to the dynamic loading code in `enable' to support
Tenon's MachTen.
n. A fix was made to the globbing code so that extended globbing patterns
will correctly match `.' in a bracket expression.
2. Changes to Readline
a. A fix was made to the completion code in which a typo caused the wrong
value to be passed to the function that computed the longest common
prefix of the list of matches.
b. The completion code now checks the value of rl_filename_completion_desired,
which is set by application-supplied completion functions to indicate
that filename completion is being performed, to decide whether or not to
call an application-supplied `ignore completions' function.
3. New Features in Bash
a. A change was made to the startup file code so that any shell begun with
the `--login' option, even non-interactive shells, will source the login
shell startup files.
4. New Features in Readline
a. A new variable, rl_erase_empty_line, which, if set by an application using
readline, will cause readline to erase, prompt and all, lines on which the
only thing typed was a newline.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.03-alpha,
and the previous version, bash-2.02.1-release.
1. Changes to Bash
a. System-specific configuration changes were made for: Irix 6.x, Unixware 7.
b. The texi2dvi and texi2html scripts were updated to the latest versions
from the net.
c. The configure tests that determine which native type is 32 bits were
changed to not require a compiled program.
d. Fixed a bug in shell_execve that could cause memory to be freed twice
after a failed exec.
e. The `printf' test uses `diff -a' if it's available to prevent confusion
due to the non-ascii output.
f. Shared object configuration is now performed by a shell script,
support/shobj-conf, which generates values to be substituted into
makefiles by configure.
g. Some changes were made to `ulimit' to avoid the use of RLIM_INVALID as a
return value.
h. Changes were made to `ulimit' to work around HPUX 9.x's peculiar
handling of RLIMIT_FILESIZE.
i. Some new loadable builtins were added: id, printenv, sync, whoami, push,
mkdir. `pushd', `popd', and `dirs' can now be built as regular or
loadable builtins from the same source file.
j. Changes were made to `printf' to handle NUL bytes in the expanded format
string.
k. The various `make clean' Makefile targets now descend into lib/sh.
l. The `type' builtin was changed to use the internal `getopt' so that things
like `type -ap' work as expected.
m. There is a new configuration option, --with-installed-readline, to link
bash with a locally-installed version of readline. Only readline version
4.0 and later releases can support this. Shared and static libraries
are supported. The installed include files are used.
n. There is a new autoconf macro used to find which basic type is 64 bits.
o. Dynamic linking and loadable builtins should now work on SCO 3.2v5*,
AIX 4.2 with gcc, Unixware 7, and many other systems using gcc, where
the `-shared' options works correctly.
p. A bug was fixed in the bash filename completion code that caused memory to
be freed twice if a directory name containing an unset variable was
completed and the -u option was set.
q. The prompt expansion code now quotes the `$' in the `\$' expansion so it
is not processed by subsequent parameter expansion.
r. Fixed a parsing bug that caused a single or double quote after a `$$' to
trigger ANSI C expansion or locale translation.
s. Fixed a bug in the globbing code that caused quoted filenames containing
no globbing characters to sometimes be incorrectly expanded.
t. Changes to the default prompt strings if prompt string decoding is not
compiled into the shell.
u. Added `do', `then', `else', `{', and `(' to the list of keywords that may
precede the `time' reserved word.
v. The shell may now be cross-built for BeOS as well as cygwin32.
w. The conditional command execution code now treats `=' the same as `=='
for deciding when to perform pattern matching.
x. The `-e' option no longer causes the shell to exit if a command exits
with a non-zero status while running the startup files.
y. The `printf' builtin no longer dumps core if a modifier is supplied in
the format string without a conversion character (e.g. `%h').
z. Array assignments of the form a=(...) no longer show up in the history
list.
aa. The parser was fixed to obey the POSIX.2 rules for finding the closing
`}' in a ${...} expression.
bb. The history file is now opened with mode 0600 rather than 0666, so bash
no longer relies on the user's umask being set appropriately.
cc. Setting LANG no longer causes LC_ALL to be assigned a value; bash now
relies on proper behavior from the C library.
dd. Minor changes were made to allow quoted variable expansions using
${...} to be completed correctly if there is no closing `"'.
ee. Changes were made to builtins/Makefile.in so that configuring the shell
with `--enable-profiling' works right and builtins/mkbuiltins is
generated.
2. Changes to Readline
a. The version number is now 4.0.
b. There is no longer any #ifdef SHELL code in the source files.
c. Some changes were made to the key binding code to fix memory leaks and
better support Win32 systems.
d. Fixed a silly typo in the paren matching code -- it's microseconds, not
milliseconds.
e. The readline library should be compilable by C++ compilers.
f. The readline.h public header file now includes function prototypes for
all readline functions, and some changes were made to fix errors in the
source files uncovered by the use of prototypes.
g. The maximum numeric argument is now clamped at 1000000.
h. Fixes to rl_yank_last_arg to make it behave better.
i. Fixed a bug in the display code that caused core dumps if the prompt
string length exceeded 1024 characters.
j. The menu completion code was fixed to properly insert a single completion
if there is only one match.
k. A bug was fixed that caused the display code to improperly display tabs
after newlines.
3. New Features in Bash
a. New `shopt' option, `restricted_shell', indicating whether or not the
shell was started in restricted mode, for use in startup files.
b. Filename generation is now performed on the words between ( and ) in
array assignments (which it probably should have done all along).
c. OLDPWD is now auto-exported, as POSIX.2 seems to require.
d. ENV and BASH_ENV are read-only variables in a restricted shell.
4. New Features in Readline
a. Many changes to the signal handling:
o Readline now catches SIGQUIT and cleans up the tty before returning;
o A new variable, rl_catch_signals, is available to application writers
to indicate to readline whether or not it should install its own
signal handlers for SIGINT, SIGTERM, SIGQUIT, SIGALRM, SIGTSTP,
SIGTTIN, and SIGTTOU;
o A new variable, rl_catch_sigwinch, is available to application
writers to indicate to readline whether or not it should install its
own signal handler for SIGWINCH, which will chain to the calling
applications's SIGWINCH handler, if one is installed;
o There is a new function, rl_free_line_state, for application signal
handlers to call to free up the state associated with the current
line after receiving a signal;
o There is a new function, rl_cleanup_after_signal, to clean up the
display and terminal state after receiving a signal;
o There is a new function, rl_reset_after_signal, to reinitialize the
terminal and display state after an application signal handler
returns and readline continues
b. There is a new function, rl_resize_terminal, to reset readline's idea of
the screen size after a SIGWINCH.
c. New public functions: rl_save_prompt and rl_restore_prompt. These were
previously private functions with a `_' prefix.
d. New function hook: rl_pre_input_hook, called just before readline starts
reading input, after initialization.
e. New function hook: rl_display_matches_hook, called when readline would
display the list of completion matches. The new function
rl_display_match_list is what readline uses internally, and is available
for use by application functions called via this hook.
f. New bindable function, delete-char-or-list, like tcsh.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.02.1-release,
and the previous version, bash-2.02-release.
1. Changes to Bash
a. A bug that caused the bash readline support to not compile unless aliases
and csh-style history were configured into the shell was fixed.
b. Fixed a bug that could cause a core dump when here documents contained
more than 1000 characters.
c. Fixed a bug that caused a CDPATH entry of "" to not be treated the same
as the current directory when in POSIX mode.
d. Fixed an alignment problem with the memory returned by the bash malloc,
so returned memory is now 64-bit aligned.
e. Fixed a bug that caused command substitutions executed within pipelines
to put the terminal in the wrong process group.
f. Fixes to support/config.sub for: alphas, SCO Open Server and Open Desktop,
Unixware 2, and Unixware 7.
g. Fixes to the pattern matching code to make it work correctly for eight-bit
characters.
h. Fixed a problem that occasionally caused the shell to display the wrong
value for the new working directory when changing to a directory found
in $CDPATH when in physical mode.
i. Fixed a bug that caused core dumps when using conditional commands in
shell functions.
j. Fixed a bug that caused the printf builtin to loop forever if the format
string did not consume any of the arguments.
k. Fixed a bug in the parameter expansion code that caused "$@" to be
incorrectly split if $IFS did not contain a space character.
l. Fixed a bug that could cause a core dump when completing hostnames if
the number of matching hostnames was an exact multiple of 16.
m. Fixed a bug that caused the shell to fork too early when a command
such as `%2 &' was given.
2. Changes to Readline
a. Fixed a problem with redisplay that showed up when the prompt string was
longer than the screen width and the prompt contained invisible characters.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.02-release,
and the previous version, bash-2.02-beta2.
1. Changes to Bash
a. A bug was fixed that caused the terminal process group to be set
incorrectly when performing command substitution of builtins in a
pipeline.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.02-beta2,
and the previous version, bash-2.02-beta1.
1. Changes to Bash
a. Attempting to `wait' for stopped jobs now generates a warning message.
b. Pipelines which exit due to SIGPIPE in non-interactive shells are now
not reported if the shell is compiled -DDONT_REPORT_SIGPIPE.
c. Some changes were made to builtins/psize.sh and support/bashbug.sh to
attempt to avoid some /tmp file races and surreptitious file
substitutions.
d. Fixed a bug that caused the shell not to compile if configured with
dparen arithmetic but without aliases.
e. Fixed a bug that caused the input stream to be switched when assigning
empty arrays with `bash -c'.
f. A bug was fixed in the readline expansion glue code that caused bash to
dump core when expanding lines with an unclosed single quote.
g. A fix was made to the `cd' builtin so that using a non-empty directory
from $CDPATH results in an absolute pathname of the new current working
directory to be displayed after the current directory is changed.
h. Fixed a bug in the variable assignment code that caused the shell to
dump core when referencing an unset variable with `set -u' enabled in
an assignment statement preceding a command.
i. Fixed a bug in the exit trap code that caused reserved words to not be
recognized under certain circumstances.
j. Fixed a bug in the parameter pattern substitution code so that quote
removal is performed.
k. The shell should now configure correctly on Apple Rhapsody systems.
l. The `kill' builtin now prints a usage message if it is not passed any
arguments.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.02-beta1,
and the previous version, bash-2.02-alpha1.
1. Changes to Bash
a. A few compilation bugs were fixed in the new extended globbing code.
b. Executing arithmetic commands now sets the command name to `((' so
error messages look right.
c. Fixed some build problems with various configuration options.
d. The `printf' builtin now aborts immediately if an illegal format
character is encountered.
e. The code that creates here-documents now behaves better if the file it's
trying to create already exists for some reason.
f. Fixed a problem with the extended globbing code that made patterns like
`x+*' expand incorrectly.
g. The prompt string expansion code no longer quotes tildes with backslashes.
h. The bash getcwd() implementation in lib/sh/getcwd.c now behaves better in
the presence of lstat(2) failures.
i. Fixed a bug with strsub() that caused core dumps when executing `fc -s'.
j. The mail checking code now ensures that it has a valid default mailpath.
k. A bug was fixed that caused local variables to be unset inappropriately
when sourcing a script from within another sourced script.
l. A bug was fixed in the history saving code so that functions are saved
in the history list correctly if `cmdhist' is enabled, but `lithist'
is not.
m. A bug was fixed that caused printf overflows when displaying error
messages.
n. It should be easier to build the loadble builtins in examples/loadables,
though some manual editing of the generated Makefile is still required.
o. The user's primary group is now always ${GROUPS[0]}.
p. Some updates were made to support/config.guess from the GNU master copy.
q. Some changes were made to the autoconf support for Solaris 2.6 large
files.
r. The `command' builtins now does the right thing when confstr(3) cannot
find a value for _CS_PATH.
s. Extended globbing expressions like `*.!(c)' are not history expanded if
`extglob' is enabled.
t. Using the `-P' option to `cd' will force the value that is assigned to
PWD to not contain any symbolic links.
2. Changes to Readline
a. The code that prints completion listings now behaves better if one or
more of the filenames contains non-printable characters.
b. The time delay when showing matching parentheses is now 0.5 seconds.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.02-alpha1,
and the previous version, bash-2.01.1-release.
1. Changes to Bash
a. OS-specific configuration changes for: BSD/OS 3.x, Minix 2.x,
Solaris 2.6, SINIX SVR4.
b. Changes were made to the generated `info' files so that `install-info'
works correctly.
c. PWD is now auto-exported.
d. A fix was made to the pipeline code to make sure that the shell forks
to execute simple commands consisting solely of assignment statements.
e. Changes to the test suite for systems with 14-character filenames.
f. The default sizes of some internal hash tables have been made smaller
to reduce the shell's memory footprint.
g. The `((...))' arithmetic command is now executed directly instead of
being translated into `let "..."'.
h. Fixes were made to the expansion code so that "$*", "$@", "${array[@]}",
and "${array[@]}" expand correctly when IFS does not contain a space
character, is unset, or is set to NULL.
i. The indirect expansion code (${!var}) was changed so that the only
valid values of `var' are variable names, positional parameters, `#',
`@', and `*'.
j. An arithmetic expression error in a $((...)) expansion now causes a
non-interactive shell running in posix mode to exit.
k. Compound array assignment now splits the words within the parentheses
on shell metacharacters like the parser would before expansing them
and performing the assignment. This is for compatibility with ksh-93.
l. The internal shell backslash-quoting code (used in the output of `set'
and completion) now quotes tildes if they appear at the start of the
string or after a `=' or `:'.
m. A couple of bugs with `shopt -o' were fixed.
n. `bash +o' now displays the same output as `set +o' before starting an
interactive shell.
o. A bug that caused command substitution and the `eval' builtin to
occasionally free memory twice when an error was encountered was fixed.
p. The filename globbing code no longer requires read permission for a
directory when the filename to be matched does not contain any globbing
characters, as POSIX.2 specifies.
q. A bug was fixed so that the job containing the last asynchronous
process is not removed from the job table until a `wait' is executed
for that process or another asynchronous process is started. This
satisfies a POSIX.2 requirement.
r. A `select' bug was fixed so that a non-numeric user response is treated
the same as a numeric response that is out of range.
s. The shell no longer parses the value of SHELLOPTS from the environment
if it is restricted, running setuid, or running in `privileged mode'.
t. Fixes were made to enable large file support on systems such as
Solaris 2.6, where the size of a file may be larger than can be held
in an `int'.
u. The filename hashing code was fixed to not add `./' to the beginning of
filenames which already begin with `./'.
v. The configure script was changed so that the GNU termcap library is not
compiled in if `prefer-curses' has been specified.
w. HISTCONTROL and HISTIGNORE are no longer applied to the second and
subsequent lines of a multi-line command.
x. A fix was made to `disown' so that it does a better job of catching
out-of-range jobs.
y. Non-interactive shells no longer report the status of processes terminated
due to SIGINT, even if the standard output is a terminal.
z. A bug that caused the output of `jobs' to have extra carriage returns
was fixed.
aa. A bug that caused PIPESTATUS to not be set when builtins or shell
functions were executed in the foreground was fixed.
bb. Bash now attempts to detect when it is being run by sshd, and treats
that case identically to being run by rshd.
cc. A bug that caused `set -a' to export SHELLOPTS when one of the shell
options was changed was fixed.
dd. The `kill' builtin now disallows empty or missing process id arguments
instead of treating them as identical to `0', which means the current
process.
ee. `var=value declare -x var' now behaves identically to
`var=value export var'. Similarly for `var=value declare -r var' and
`var=value readonly var'.
ff. A few memory leaks were fixed.
gg. `alias' and `unalias' now print error messages when passed an argument
that is not an alias for printing or deletion, even when the shell is
not interactive, as POSIX.2 specifies.
hh. `alias' and `alias -p' now return a status of 0 when no aliases are
defined, as POSIX.2 specifes.
ii. `cd -' now prints the pathname of the new working directory if the shell
is interactive.
jj. A fix was made so that the code that binds $PWD now copes with getcwd()
returning NULL.
kk. `unset' now checks whether or not a function name it's trying to unset
is a valid shell identifier only when the shell is running in posix mode.
ll. A change was made to the code that generates filenames for here documents
to make them less prone to name collisions.
mm. The parser was changed so that `time' is recognized as a reserved word
only at the beginning of a pipeline.
nn. The pathname canonicalization code was changed so that `//' is converted
into `/', but all other pathnames beginning with `//' are left alone, as
POSIX.2 specifies.
oo. The `logout' builtin will no longer exit a non-interactive non-login
shell.
2. Changes to Readline
a. Fixed a problem in the readline test program rltest.c that caused a core
dump.
b. The code that handles parser directives in inputrc files now displays
more error messages.
c. The history expansion code was fixed so that the appearance of the
history comment character at the beginning of a word inhibits history
expansion for that word and the rest of the input line.
3. New Features in Bash
a. A new version of malloc, based on the older GNU malloc, that has many
changes, is more page-based, is more conservative with memory usage,
and does not `orphan' large blocks when they are freed.
b. A new version of gmalloc, based on the old GLIBC malloc, with many
changes and range checking included by default.
c. A new implementation of fnmatch(3) that includes full POSIX.2 Basic
Regular Expression matching, including character classes, collating
symbols, equivalence classes, and support for case-insensitive pattern
matching.
d. ksh-88 egrep-style extended pattern matching ([@+*?!](patlist)) has been
implemented, controlled by a new `shopt' option, `extglob'.
e. There is a new ksh-like `[[' compound command, which implements
extended `test' functionality.
f. There is a new `printf' builtin, implemented according to the POSIX.2
specification.
g. There is a new feature for command substitution: $(< filename) now expands
to the contents of `filename', with any trailing newlines removed
(equivalent to $(cat filename)).
h. There are new tilde prefixes which expand to directories from the
directory stack.
i. There is a new `**' arithmetic operator to do exponentiation.
j. There are new configuration options to control how bash is linked:
`--enable-profiling', to allow bash to be profiled with gprof, and
`--enable-static-link', to allow bash to be linked statically.
k. There is a new configuration option, `--enable-cond-command', which
controls whether or not the `[[' command is included. It is on by
default.
l. There is a new configuration option, `--enable-extended-glob', which
controls whether or not the ksh extended globbing feature is included.
It is enabled by default.
m. There is a new configuration #define in config.h.top that, when enabled,
will cause all login shells to source /etc/profile and one of the user-
specific login shell startup files, whether or not the shell is
interactive.
n. There is a new invocation option, `--dump-po-strings', to dump
a shell script's translatable strings ($"...") in GNU `po' format.
o. There is a new `shopt' option, `nocaseglob', to enable case-insensitive
pattern matching when globbing filenames and using the `case' construct.
p. There is a new `shopt' option, `huponexit', which, when enabled, causes
the shell to send SIGHUP to all jobs when an interactive login shell
exits.
q. `bind' has a new `-u' option, which takes a readline function name as an
argument and unbinds all key sequences bound to that function in a
specified keymap.
r. `disown' now has `-a' and `-r' options, to limit operation to all jobs
and running jobs, respectively.
s. The `shopt' `-p' option now causes output to be displayed in a reusable
format.
t. `test' has a new `-N' option, which returns true if the filename argument
has been modified since it was last accessed.
u. `umask' now has a `-p' option to print output in a reusable format.
v. A new escape sequence, `\xNNN', has been added to the `echo -e' and $'...'
translation code. It expands to the character whose ascii code is NNN
in hexadecimal.
w. The prompt string expansion code has a new `\r' escape sequence.
x. The shell may now be cross-compiled for the CYGWIN32 environment on
a Unix machine.
4. New Features in Readline
a. There is now an option for `iterative' yank-last-arg handline, so a user
can keep entering `M-.', yanking the last argument of successive history
lines.
b. New variable, `print-completions-horizontally', which causes completion
matches to be displayed across the screen (like `ls -x') rather than up
and down the screen (like `ls').
c. New variable, `completion-ignore-case', which causes filename completion
and matching to be performed case-insensitively.
d. There is a new bindable command, `magic-space', which causes history
expansion to be performed on the current readline buffer and a space to
be inserted into the result.
e. There is a new bindable command, `menu-complete', which enables tcsh-like
menu completion (successive executions of menu-complete insert a single
completion match, cycling through the list of possible completions).
f. There is a new bindable command, `paste-from-clipboard', for use on Win32
systems, to insert the text from the Win32 clipboard into the editing
buffer.
g. The key sequence translation code now understands printf-style backslash
escape sequences, including \NNN octal escapes. These escape sequences
may be used in key sequence definitions or macro values.
h. An `$include' inputrc file parser directive has been added.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.01.1-release,
and the previous version, bash-2.01-release.
1. Changes to Bash
a. The select command was fixed to check the validity of the user's
input more strenuously.
b. A bug was fixed that prevented `time' from timing commands correctly
when supplied as an argument to `bash -c'.
c. A fix was made to the mail checking code to keep from adding the same
mail file to the list of files to check multiple times when parsing
$MAILPATH.
d. Fixed an off-by-one error in the tilde expansion library.
e. When using the compound array assignment syntax, the old value of
the array is cleared before assigning the new value.
f. Fixed a bug that could cause a core dump when a trap handler was reset
to the default in the trap command associated with that signal.
g. Fixed a bug in the locale code that occurred when assigning a value
to LC_ALL.
h. A change was made to the parser so that words of the form xxx=(...)
are not considered compound assignment statements unless there are
characters before the `='.
i. A fix was made to the command tracing code to correctly quote each
word of output.
j. Some changes were made to the bash-specific autoconf tests to make them
more portable.
k. Completion of words with globbing characters now correctly quotes the
result.
l. The directory /var/spool/mail is now preferred to /usr/spool/mail when
configure is deciding on the default mail directory.
m. The brace completion code was fixed to not quote the `{' and `}'.
n. Some fixes were made to make $RANDOM more random in subshells.
o. System-specific changes were made to configure for: SVR4.2
p. Changes were made so that completion of words containing globbing chars
substitutes the result only if a single filename was matched.
q. The window size is now recomputed after a job is stopped with SIGTSTP if
the user has set `checkwinsize' with `shopt'.
r. When doing substring expansion, out-of-range substring specifiers now
cause nothing to be substituted rather than an expansion error.
s. A fix was made so that you can no longer trap `SIGEXIT' or `SIGDEBUG' --
only `EXIT' and `DEBUG' are accepted.
t. The display of trapped signals now uses the signal number if signals
for which bash does not know the name are trapped.
u. A fix was made so that `bash -r' does not turn on restricted mode until
after the startup files are executed.
v. A bug was fixed that occasionally caused a core dump when a variable
found in the temporary environment of export/declare/readonly had a
null value.
w. A bug that occasionally caused unallocated memory to be passed to free()
when doing arithmetic substitution was fixed.
x. A bug that caused a buffer overrun when expanding a prompt string
containing `\w' and ${#PWD} exceeded PATH_MAX was fixed.
y. A problem with the completion code that occasionally caused it to
refer to a character before the beginning of the readline line buffer
was fixed.
z. A bug was fixed so that the `read' builtin restarts reads when
interrupted by signals other than SIGINT.
aa. Fixed a bug that caused a command to be freed twice when there was
an evaluation error in the `eval' command.
2. Changes to Readline
a. Added a missing `extern' to a declaration in readline.h that kept
readline from compiling cleanly on some systems.
b. The history file is now opened with mode 0600 when it is written for
better security.
c. Changes were made to the SIGWINCH handling code so that prompt redisplay
is done better.
d. ^G now interrupts incremental searches correctly.
e. A bug that caused a core dump when the set of characters to be quoted
when completing words was empty was fixed.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.01-release,
and the previous version, bash-2.01-beta2.
1. Changes to Bash
a. The `distclean' target should remove the `printenv' executable if it
has been created.
b. The test suite was changed slightly to ensure that the error messages
are printed in English.
c. A bug that caused the shell to dump core when a filename containing a
`/' was passed to `hash' was fixed.
d. Pathname canonicalization now leaves a leading `//' intact, as POSIX.1
requires.
e. A memory leak when completing commands was fixed.
f. A memory leak that occurred when checking the hash table for commands
with relative paths was fixed.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.01-beta2,
and the previous version, bash-2.01-beta1.
1. Changes to Bash
a. The `ulimit' builtin translates RLIM_INFINITY to the hard limit only if
the current (soft) limit is less than or equal to the hard limit.
b. Fixed a bug that caused the bash emulation of strcasecmp to produce
incorrect results.
c. A bug that caused memory to be freed twice when a trap handler resets
the trap more than once was fixed.
d. A bug that caused machines where sizeof (pointer) > sizeof (int) to
fail (and possibly dump core) when trying to unwind-protect a null
pointer was fixed.
e. The startup files should not be run with job control enabled. This fix
allows SIGINT to once again interrupt startup file execution.
f. Bash should not change the SIGPROF handler if it is set to something
other than SIG_DFL.
g. The completion code that provides bash-specific completions for readline
now quotes characters that the readline code would treat as word break
characters if they appear in a file name.
h. The completion code now correctly quotes filenames containing a `!',
even if the user attempted to use double quotes when attempting
completion.
i. A bug that caused the shell to dump core when `disown' was called without
arguments and there was no current job was fixed.
j. A construct like $((foo);bar) is now processed as a command substitution
rather than as a bad arithmetic substitution.
k. A couple of bugs that caused `fc' to not obey the `cmdhist' and `lithist'
shell options when editing and re-executing a series of commands were
fixed.
l. A fix was made to the grammar -- the list of commands between `do' and
`done' in the body of a `for' command should be treated the same as a
while loop.
2. Changes to Readline
a. A couple of bugs that caused the history search functions to attempt to
free a NULL pointer were fixed.
b. If the C library provides setlocale(3), readline does not need to look
at various environment variables to decide whether or not to go into
eight-bit mode automatically -- just check whether the current locale
is not `C' or `POSIX'.
c. If the filename completion function finds that a directory was not closed
by a previous (interrupted) completion, it closes the directory with
closedir().
3. New Features in Bash
a. New bindable readline commands: history-and-alias-expand-line and
alias-expand-line. The code was always in there, there was just no
way to execute it.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.01-beta1,
and the previous version, bash-2.01-alpha1.
1. Changes to Bash
a. Fixed a problem that could cause file descriptors used for process
substitution to conflict with those used explicitly in redirections.
b. Made it easier to regenerate configure if the user changes configure.in.
c. ${GROUPS[0]} should always be the primary group, even on systems without
multiple groups.
d. Spelling correction is no longer enabled by default.
e. Fixes to quoting problems in `bashbug'.
f. OS-specific configuration changes were made for: Irix 6.
g. OS-specific code changes were made for: QNX.
h. A more meaningful message is now printed when the file in /tmp for a
here document cannot be created.
i. Many changes to the shell's variable initialization code to speed
non-interactive startup.
j. Changes to the non-job-control code so that it does not try to open
/dev/tty.
k. The output of `set' and `export' is once again sorted, as POSIX wants.
l. Fixed a problem caused by a recursive call reparsing the value of
$SHELLOPTS.
m. The tilde code no longer calls getenv() when it's compiled as part of
the shell, which should eliminate problems on systems that cannot
redefine getenv(), like the NeXT OS.
n. Fixed a problem that caused `bash -o' or `bash +o' to not list all
the shell options.
o. Fixed `ulimit' to convert RLIM_INFINITY to the appropriate hard limit
only if the hard limit is greater than the current (soft) limit.
p. Fixed a problem that arose when building bash in a different directory
than the source and y.tab.[ch] were remade with something other than
bison. This came up most often on NetBSD.
q. Fixed a problem with completion -- it thought that `pwd`/[TAB] indicated
an unfinished command completion (`/), which generated errors.
r. The bash special tilde expansions (~-, ~+) are now attempted before
calling the standard tilde expansion code, which should eliminate the
problems people have been seeing with this on Solaris 2.5.1.
s. Added support for to places where it was missing.
t. Changed the code that reads the output of a command substitution to not
go through stdio. This reduces the memory requirements and is faster.
u. A number of changes to speed up export environment creation were made.
v. A number of memory leaks were fixed as the result of running the test
scripts through Purify.
w. Fixed a bug that caused subshells forked to interpret executable
scripts without a leading `#!' to not reinitialize the values of
the shell options.
2. Changes to Readline
a. History library has less `#ifdef SHELL' code -- abstracted stuff out
into application-specific function hooks.
b. Readline no longer calls getenv() if it's compiled as part of the shell,
which should eliminate problems on systems that cannot redefine getenv(),
like the NeXT OS.
c. Fixed translation of ESC when `untranslating' macro values.
d. The region kill operation now fixes the mark if it ends up beyond the
boundaries of the line after the region is deleted.
3. New Features in Bash
a. New argument for `configure': `--with-curses'. This can be used to
override the selection of the termcap library on systems where it is
deficient.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.01-alpha1,
and the previous version, bash-2.0-release.
1. Changes to Bash
a. System-specific configuration changes for: FreeBSD, SunOS4, Irix,
MachTen, QNX 4.2, Harris Night Hawk, SunOS5.
b. System-specific code changes were made for: Linux, 4.4 BSD, QNX 4.2,
HP-UX, AIX 4.2.
c. A bug that caused the exec builtin to fail because the full pathname of
the command could not be found was fixed.
d. The code that performs output redirections is now more resistant to
race conditions and possible security exploits.
e. A bug that caused the shell to dump core when performing pattern
substitutions on variable values was fixed.
f. More hosts are now recognized by the auto-configuration mechanism
(OpenBSD, QNX, others).
g. Assignments to read-only variables that attempt to convert them to
arrays are now errors.
h. A bug that caused shell scripts using array assignments in POSIX mode
to exit after the assignment was performed was fixed.
i. The substring expansion code is now more careful about running off the
ends of the expanded variable value.
j. A bug that caused completion to fail if a backquoted command substitution
appeared anywhere on the line was fixed.
k. The `source' builtin no longer turns off history if it has been enabled
in a non-interactive shell.
l. A bug that caused the shell to crash when `disown' was given a pid
instead of a job number was fixed.
m. The `cd' spelling correction code will not try to change to `.' if no
directory entries match a single-character argument.
n. A bad variable name supplied to `declare', `export', or `readonly' no
longer causes a non-interactive shell in POSIX mode to exit.
o. Some fixes were made to the test suite to handle peculiarities of
various Unix versions.
p. The bash completion code now quotes characters that readline would
treat as word breaks for completion but are not shell metacharacters.
q. Bad options supplied at invocation now cause a usage message to be
displayed.
r. Fixes were made to the code that handles DEBUG traps so that the trap
string is not freed inappropriately.
s. Some changes were made to the bash debugger in examples/bashdb -- it
should be closer to working now.
t. A problem that caused the default filename used for mail checking to be
wrong was fixed.
u. A fix was made to the `echo' builtin so that NUL characters printed with
`echo -e' do not cause the output to be truncated.
v. A fix was made to the job control code so that the shell behaves better
when monitor mode is enabled in a non-interactive shell.
w. Bash no longer catches all of the terminating signals in a non-
interactive shell until a trap is set on EXIT, which should result in
quicker startup.
x. A fix was made to the command timing code so that `time' can be used in
a loop.
y. A fix was made to the parser so that `((cmd); cmd2)' is now parsed as
a nested subshell rather than strictly as an (erroneous) arithmetic
command.
z. A fix was made to the globbing code so that it correctly matches quoted
filenames beginning with a `.'.
aa. A bug in `fc' that caused some multi-line commands to not be stored as
one command in the history when they were re-executed after editing
(with `fc -e') was fixed.
bb. The `ulimit' builtin now attempts to catch some classes of integer
overflows.
cc. The command-oriented-history code no longer attempts to add `;'
inappropriately when a newline appears while reading a $(...) command
substitution.
dd. A bug that caused the shell to dump core when `help --' was executed
was fixed.
ee. A bug that caused the shell to crash when an unset variable appeared
in the body of a here document after `set -u' had been executed was
fixed.
ff. Implicit input redirections from /dev/null for asynchronous commands
are now handled better.
gg. A bug that caused the shell to fail to compile when configured with
`--disable-readline' was fixed.
hh. The globbing code should now be interruptible.
ii. Bash now notices when the `kill' builtin is used to send SIGCONT to a
stopped job and adjusts the data structures accordingly, as if `bg' had
been executed instead.
jj. A bug that caused the shell to crash when mixing calls to `getopts'
and `shift' on the same set of positional parameters was fixed.
kk. The command printing code now preserves the `-p' flag to `time'.
ll. The command printing code now handles here documents better when there
are other redirections associated with the command.
mm. The special glibc environment variable (NNN_GNU_nonoption_argv_flags_)
is no longer placed into the environment of executed commands -- users
of glibc had too many problems with it.
nn. Reorganized the code that generates signames.h. The signal_names list
is now more complete but may be slightly different (SIGABRT is favored
over SIGIOT, for example). The preferred signal names are those
listed in the POSIX.2 standard.
oo. `bashbug' now uses a filename shorter than 14 characters for its
temporary file, and asks for confirmation before sending the bug
report.
pp. A bug that caused TAB completion in vi editing mode to not be turned
off when `set -o posix' was executed or back on when `set +o posix'
was executed was fixed.
qq. A bug in the brace expansion code that caused brace expansions appearing
in new-style $(...) command substitutions to be inappropriately expanded
was fixed.
rr. A bug in the readline hook shell-expand-line that could cause memory to
be inappropriately freed was fixed.
ss. A bug that caused some arithmetic expressions containing `&&' and `||'
to be parsed with the wrong precedence has been fixed.
tt. References to unbound variables after `set -u' has been executed now
cause the shell to exit immediately, as they should.
uu. A bug that caused the shell to exit inappropriately when `set -e' had
been executed and a command's return status was being inverted with the
`!' reserved word was fixed.
vv. A bug that could occasionally cause the shell to crash with a
divide-by-zero error when timing a command was fixed.
ww. A bug that caused parameter pattern substitution to leave stray
backslashes in the replacement string when the expression is in
double quotes was fixed.
xx. The `break' and `continue' builtins now break out of all loops when an
invalid count argument is supplied.
yy. Fixed a bug that caused PATH to be set to the empty string if
`command -p' is executed with PATH unset.
zz. Fixed `kill -l signum' to print the signal name without the `SIG' prefix,
as POSIX specifies.
aaa. Fixed a bug that caused the shell to crash while setting $SHELLOPTS
if there were no shell options set.
bbb. Fixed `export -p' and `readonly -p' so that when the shell is in POSIX
mode, their output is as POSIX.2 specifies.
ccc. Fixed a bug in `readonly' so that `readonly -a avar=(...)' actually
creates an array variable.
ddd. Fixed a bug that prevented `time' from correctly timing background
pipelines.
2. Changes to Readline
a. A bug that caused an extra newline to be printed when the cursor was on
an otherwise empty line was fixed.
b. An instance of memory being used after it was freed was corrected.
c. The redisplay code now works when the prompt is longer than the screen
width.
d. `dump-macros' is now a bindable name, as it should have been all along.
e. Non-printable characters are now expanded when displaying macros and
their values.
f. The `dump-variables' and `dump-macros' commands now output a leading
newline if they're called as the result of a key sequence, rather
than directly by an application.
3. New Features in Bash
a. There is a new builtin array variable: GROUPS, the set of groups to which
the user belongs. This is used by the test suite.
4. New Features in Readline
a. If a key sequence bound to `universal-argument' is read while reading a
numeric argument started with `universal-argument', it terminates the
argument but is otherwise ignored. This provides a way to insert multiple
instances of a digit string, and is how GNU emacs does it.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.0-release,
and the previous version, bash-2.0-beta3.
1. Changes to Bash
a. Fix to the `getopts' builtin so that it does the right thing when a
required option argument is not present.
b. The completion code now updates the common prefix of matched names
after FIGNORE processing is done, since any names that were removed
may have changed the common prefix.
c. Fixed a bug that made messages in MAILPATH entries not work correctly.
d. Fixed a serious documentation error in the description of the new
${parameter:offset[:length]} expansion.
e. Fixes to make parameter substring expansion ({$param:offset[:length]})
work when within double quotes.
f. Fixes to make ^A (CTLESC) survive an unquoted expansion of positional
parameters.
g. Corrected a misspelling of `unlimited' in the output of `ulimit'.
h. Fixed a bug that caused executable scripts without a leading `#!' to
occasionally pick up the wrong set of positional parameters.
i. Linux systems now have a working `ulimit -v', using RLIMIT_AS.
j. Updated config.guess so that many more machine types are recognized.
k. Fixed a bug with backslash-quoted slashes in the ${param/pat[/sub]}
expansion.
l. If the shell is named `-su', and `-c command' is supplied, read and
execute the login shell startup files even though the shell is not
interactive. This is to support the `-' option to `su'.
m. Fixed a bug that caused core dumps when the DEBUG trap was ignored
with `trap "" DEBUG' and a shell function was subsequently executed.
n. Fixed a bug that caused core dumps in the read builtin when IFS was
set to the null string and the input had leading whitespace.
2. Changes to Readline
a. Fixed a bug that caused a numeric argument of 1024 to be ignored when
inserting text.
b. Fixed the display code so that the numeric argument is displayed as it's
being entered.
c. Fixed the numeric argument reading code so that `M-- command' is
equivalent to `M--1 command', as the prompt implies.
3. New Features in Bash
a. `ulimit' now sets both hard and soft limits and reports the soft limit
by default (when neither -H nor -S is specified). This is compatible
with versions of sh and ksh that implement `ulimit'.
b. Integer constants have been extended to base 64.
4. New Features in Readline
a. The `home' and `end' keys are now bound to beginning-of-line and
end-of-line, respectively, if the corresponding termcap capabilities
are present.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.0-beta3,
and the previous version, bash-2.0-beta2.
1. Changes to Bash
a. System-specific changes for: AIX 4.2, SCO 3.2v[45], HP-UX.
b. When in POSIX mode, variable assignments preceding a special builtin
persist in the shell environment after the builtin completes.
c. Changed all calls to getwd() to getcwd(). Improved check for systems
where the libc getcwd() calls popen(), since that breaks on some
systems when job control is being used.
d. Fixed a bug that caused seg faults when executing scripts with the
execute bit set but without a leading `#!'.
e. The environment passed to executed commands is never sorted.
f. A bug was fixed in the code that expands ${name[@]} to the number of
elements in an array variable.
g. A bug was fixed in the array compound assignment code ( A=( ... ) ).
h. Window size changes now correctly propagate down to readline if
the shopt `checkwinsize' option is enabled.
i. A fix was made in the code that expands to the length of a variable
value (${#var}).
j. A fix was made to the command builtin so that it did not turn on the
`no fork' flag inappropriately.
k. A fix was made to make `set -n' work more reliably.
l. A fix was made to the job control initialization code so that the
terminal process group is set to the shell's process group if the
shell changes its own process group.
2. Changes to Readline
a. System-specific changes for: SCO 3.2v[45].
b. The behavior of the vi-mode `.' when redoing an `i' command was changed
to insert the text previously inserted by the `i' command rather than
simply entering insert mode.
3. New features in Bash
a. There is a new version of the autoload function package, in
examples/functions/autoload.v2, that uses arrays and provides more
functionality.
b. Support for LC_COLLATE and locale-specific sorting of the results of
pathname expansion if strcoll() is available.
4. New Features in Readline
a. Support for locale-specific sorting of completion possibilities if
strcoll() is available.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.0-beta2,
and the previous version, bash-2.0-beta1.
1. Changes to Bash
a. `pushd -' is once again equivalent to `pushd $OLDPWD'.
b. OS-specific changes for: SCO 3.2v[45].
c. A change was made to the fix for the recently-reported security hole
when reading characters with octal value 255 to make it work better on
systems with restartable system calls when not using readline.
d. Some changes were made to the test suite so that it works if you
configure bash with --enable-usg-echo-default.
e. A fix was made to the parsing of conditional arithmetic expressions.
f. Illegal arithmetic bases now cause an arithmetic evaluation error rather
than being silently reset.
g. Multiple arithmetic bases now cause an arithmetic evaluation error
instead of being ignored.
h. A fix was made to the evaluation of ${param?word} to conform to POSIX.2.
i. A bug that sometimes caused array indices to be evaluated twice (which
would cause errors when they contained assignment statements) was fixed.
j. `ulimit' was rewritten to avoid problems with getrlimit(2) returning
unsigned values and to simplify the code.
k. A bug in the command-oriented-history code that caused it to sometimes
put semicolons after right parens inappropriately was fixed.
l. The values inserted into the prompt by the \w and \W escape sequences
are now quoted to prevent further expansion.
m. An interactive shell invoked as `sh' now reads and executes commands
from the file named by $ENV when it starts up. If it's a login shell,
it does this after reading /etc/profile and ~/.profile.
n. The file named by $ENV is never read by non-interactive shells.
2. Changes to Readline
a. A few changes were made to hide some macros and functions that should not
be public.
b. An off-by-one error that caused seg faults in the history expansion code
was fixed.
3. New Features in Bash
a. The ksh-style ((...)) arithmetic command was implemented. It is exactly
identical to let "...". This is controlled by a new option to configure,
`--enable-dparen-arithmetic', which is on by default.
b. There is a new #define available in config.h.top: SYS_BASH_LOGOUT. If
defined to a filename, bash reads and executes commands from that file
when a login shell exits. It's commented out by default.
c. `ulimit' has a `-l' option that reports the maximum amount of data that
may be locked into memory on 4.4BSD-based systems.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.0-beta1,
and the previous version, bash-2.0-alpha4.
1. Changes to Bash
a. A bug that sometimes caused traps to be ignored on signals the
shell treats specially was fixed.
b. The internationalization code was changed to track the values of
LC_* variables and call setlocale() as appropriate. The TEXTDOMAIN
and TEXTDOMAINDIR variables are also tracked; changes cause calls
to textdomain() and bindtextdomain(), if available.
c. A bug was fixed that sometimes caused double-quoted strings to be
parsed incorrectly.
d. Changes were made so that the siglist code compiles correctly on
Solaris 2.5.
e. Added `:' to the set of characters that cause word breaks for the
completion code so that pathnames in assignments to $PATH can be
completed.
f. The `select' command was fixed to print $PS3 to stderr.
g. Fixed an error in the manual page section describing the effect that
setting and unsetting GLOBIGNORE has on the setting of the `dotglob'
option.
h. The time conversion code now uses CLK_TCK rather than CLOCKS_PER_SEC
on systems without gettimeofday() and resources.
i. The getopt static variables are now initialized each time a subshell
is started, so subshells using `getopts' work right.
j. A sign-extension bug that caused a possible security hole was fixed.
k. The parser now reads characters between backquotes within a double-
quoted string as a single word, so double quotes in the backquoted
string don't terminate the enclosing double-quoted string.
l. A bug that caused `^O' to work incorrectly when typed as the first
thing to an interactive shell was fixed.
m. A rarely-exercised off-by-one error in the code that quotes variable
values was fixed.
n. Some memory and file descriptor leaks encountered when running a
shell script that is executable but does not have a leading `#!'
were plugged.
2. Changes to Readline
a. A bug that sometimes caused incorrect results when trying to read
typeahead on systems without FIONREAD was fixed.
3. New Features in Bash
a. The command timing code now uses the value of the TIMEFORMAT variable
to format and display timing statistics.
b. The `time' reserved word now accepts a `-p' option to force the
POSIX.2 output format.
c. There are a couple of new and updated scripts to convert csh startup
files to bash format.
d. There is a new builtin array variable: BASH_VERSINFO. The various
members hold the parts of the version information in BASH_VERSION,
plus the value of MACHTYPE.
4. New Features in Readline
a. Setting LANG to `en_US.ISO8859-1' now causes readline to enter
eight-bit mode.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.0-alpha4,
and the previous version, bash-2.0-alpha3.
1. Changes to Bash
a. There is better detection of rsh connections on Solaris 2.
b. Assignments to read-only variables preceding a command name are now
variable assignment errors. Variable assignment errors cause
non-interactive shells running in posix mode to exit.
c. The word tokenizer was rewritten to handle nested quotes and pairs
('', "", ``, ${...}, $(...), $[...], $'...', $"...", <(...), >(...))
correctly. Some of the parameter expansion code was updated as a
consequence.
d. A fix was made to `test' when given three arguments so that a binary
operator is checked for first, before checking that the first argument
is `!'.
e. 2''>/dev/null is no longer equivalent to 2>/dev/null.
f. Parser error messages were regularized, and in most cases the name of
the shell script being read by a non-interactive shell is not printed
twice.
g. A fix was made to the completion code so that it no longer removes the
text the user typed in some cases.
h. The special glibc `getopt' environment variable is no longer put into
the environment on machines with small values of ARG_MAX.
i. The expansion of ${...} now follows the POSIX.2 rules for finding the
closing `}'.
j. The shell no longer displays spurious status messages for background
jobs in shell scripts that complete successfully when the script is
run from a terminal.
k. `shopt -o' now correctly updates $SHELLOPTS.
l. A bug that caused the $PATH searching code to return a non-executable
file even when an executable file with the same name appeared later in
$PATH was fixed.
m. The shell now does tilde expansions on unquoted `:~' in assignment
statements when not in posix mode.
n. Variable assignment errors when a command consists only of assignments
now cause non-interactive shells to exit when in posix mode.
o. If the variable in a `for' or `select' command is read-only, or not a
legal shell identifier, a variable assignment error occurs.
p. `test' now handles `-a' and `-o' as binary operators when three arguments
are supplied, and correctly parses `( word )' as equivalent to `word'.
q. `test' was fixed so that file names of the form /dev/fd/NN mean the same
thing on all systems, even Linux.
r. Fixed a bug in the globbing code that caused patterns with multiple
consecutive `*'s to not be matched correctly.
s. Fixed a bug that caused $PS2 to not be printed when an interactive shell
not using readline is reading a here document.
t. Fixed a bug that caused history expansion to be performed inappropriately
when a single-quoted string spanned more than one line.
u. `getopts' now checks that the variable name passed by the user as the
second argument is a legal shell identifier and that the variable is
not read-only.
v. Fixed `getopts' to obey POSIX.2 rules for setting $OPTIND when it
encounters an error.
w. Fixed `set' to display variable values in a form that can be re-read.
x. Fixed a bug in the code that keeps track of whether or not local variables
have been declared at the current level of function nesting.
y. Non-interactive shells in posix mode now exit if the name in a function
declaration is not a legal identifier.
z. The job control code now ignores stopped children when the shell is not
interactive.
aa. The `cd' builtin no longer attempts spelling correction on the directory
name if the shell is not interactive, regardless of the setting of the
`cdspell' option.
bb. Some OS-specific changes were made for SCO 3.2v[45] and AIX 4.2.
cc. `time' now prints its output to stderr, as POSIX.2 specifies.
2. Fixes to Readline
a. After printing possible completions, all lines of a multi-line prompt
are redisplayed.
b. Some changes were made to the terminal handling code in rltty.c to
work around AIX 4.2 bugs.
3. New Features in Bash
a. There is a new loadable builtin: sprintf, with calling syntax
sprintf var format [args]
This provides an easy way to simulate ksh left- and right-justified
variable values.
b. The expansions of \h and \H in prompt strings were swapped. \h now
expands to the hostname up to the first `.', as in bash-1.14.
4. New Features in Readline
a. The bash-1.14 behavior when ^M is typed while doing an incremental
search was restored. ^J may now be used to terminate the search without
accepting the line.
b. There is a new bindable variable: disable-completion. This inhibits
word completion and causes the completion character to be inserted as
if it had been bound to self-insert.
------------------------------------------------------------------------------
This document details the changes between this version, bash-2.0-alpha3,
and the previous version, bash-2.0-alpha2.
There is now a file `COMPAT' included in the distribution that lists the
user-visible incompatibilities between 1.14 and 2.0.
1. Changes to Bash
a. Some work was done so that word splitting of the rhs of assignment
statements conforms more closely to historical practice.
b. A couple of errant memory frees were fixed.
c. A fix was made to the test builtin so it recognizes `<' and `>' as
binary operators.
d. The GNU malloc in lib/malloc/malloc.c now scrambles memory as it's
allocated and freed. This is to catch callers that refer to freed
memory or assume something about newly-allocated memory.
e. Fixed a problem with conversion to 12-hour time in the prompt
expansion code.
f. Fixed a problem with configure's argument parsing order. Now you can
correctly turn on specific options after using --enable-minimal-config.
g. The configure script now automatically disables the use of GNU malloc
on systems where it's appropriate (better than having people read the
NOTES file and do it manually).
h. There are new prompt expansions (\v and \V) to insert version information
into the prompt strings.
i. The default prompt string now includes the version number.
j. Most of the builtins that take no options were changed to use the
internal getopt so they can produce proper error messages for -?
and incorrect options.
k. Some system-specific changes were made for SVR4.2 and Solaris 2.5.
l. Bash now uses PATH_MAX instead of MAXPATHLEN and NAME_MAX instead of
MAXNAMLEN.
m. A couple of problems caused by uninitialized variables were fixed.
n. There are a number of new loadable builtin examples: logname, basename,
dirname, tty, pathchk, tee, head, and rmdir. All of these conform to
POSIX.2.
o. Bash now notices changes in TZ and calls tzset() if present, so
changing TZ will alter the time printed by prompt expansions.
p. The source was reorganized a bit so I don't have to wait so long for
some files to compile, and to facilitate the creation of a `shell
library' at some future point.
q. Bash no longer turns off job control if called as `sh', since the
POSIX.2 spec includes job control as a standard feature.
r. `bash -o posix' now works as intended.
s. Fixed a problem with the completion code: when completing a filename
that contained globbing characters, if show-all-if-ambiguous was set,
the completion code would remove the user's text.
t. Fixed ulimit so that (hopefully) the full range of limits is available
on HPUX systems.
u. A new `shopt' option (`hostcomplete') enables and disables hostname
completion.
v. The shell no longer attempts to save the history on an abort(),
which is usually called by programming_error().
w. The `-s' option to `fc' was changed to echo the command to be executed
to stderr instead of stdout.
x. If the editor invoked by `fc -e' exits with a non-zero status, no
commands are executed.
y. Fixed a bug that made the shopt `histverify' option work incorrectly.
z. There is a new variable `MACHTYPE' whose value is the GNU-style
`cpu-company-system' system description as set by configure. (The
values of MACHTYPE and HOSTTYPE should really be swapped.)
aa. The `ulimit' builtin now allows the maximum virtual memory size to be
set via setrlimit(2) if RLIMIT_VMEM is defined.
bb. `bash -nc 'command'' no longer runs `command'.
2. Changes to Readline
a. Fixed a typo in the code that checked for FIONREAD in input.c.
b. Fixed a bug in the code that outputs keybindings, so things like C-\
are quoted properly.
c. Fixed a bug in the inputrc file parsing code to handle the problems
caused by inputrc files created from the output of `bind -p' in
previous versions of bash. The problem was due to the bug fixed
in item b above.
d. Readline no longer turns off the terminal's meta key, and turns it on
once the first time it's called.
------------------------------------------------------------------------------
This file documents the changes between this version, bash-2.0-alpha2,
and the previous version, bash-2.0-alpha.
1. Changes to Bash
a. The shell no longer thinks directories are executable.
b. `disown' has a new option, `h', which inhibits the resending of SIGHUP
but does not remove the job from the jobs table.
c. The varargs functions in error.c now use ANSI-C `stdarg' if available.
d. The build process now treats the `build version' in .build as local to
the build directory, so different versions built from the same source
tree have different `build versions'.
e. Some problems with the grammar have been fixed. (It used `list' in a few
productions where `compound_list' was needed. A `list' must be terminated
with a newline or semicolon; a `compound_list' need not be.)
f. A fix was made to keep `wait' from hanging when waiting for all background
jobs.
g. `bash --help' now writes its output to stdout, like the GNU Coding Standards
specify, and includes the machine type (the value of MACHTYPE).
h. `bash --version' now prints more information and exits successfully, like
the GNU Coding Standards specify.
i. The output of `time' and `times' now prints fractional seconds with three
places after the decimal point.
j. A bug that caused process substitutions to screw up the pipeline printed
by `jobs' was fixed.
k. Fixes were made to the code that implements $'...' and $"..." so they
work as documented.
l. The process substitution code now opens named pipes for reading with
O_NONBLOCK to avoid hanging.
m. Fixes were made to the trap code so the shell cleans up correctly if the
trap command contains a `return' and we're executing a function or
sourcing a script with `.'.
n. Fixes to doc/Makefile.in so that it doesn't try to remake all of the
documentation (ps, dvi, etc.) on a `make install'.
o. Fixed an auto-increment error that caused bash -c args to sometimes dump
core.
p. Fixed a bug that caused $HISTIGNORE to fail when the history line
contained globbing characters.
2. Changes to Readline
a. There is a new string variable, rl_library_version, available for use by
applications. The current value is "2.1".
b. A bug encountered when expand-tilde was enabled and file completion was
attempted on a word beginning with `~/' was fixed.
c. A slight change was made to the incremental search termination behavior.
ESC still terminates the search, but if input is pending or arrives
within 0.1 seconds (on systems with select(2)), it is used as a prefix
character. This is intented to allow users to terminate searches with
the arrow keys and get the behavior they expect.
0707010007eb3a000081a40000000000000000000000015428b735000507d500000100000100b5ffffffffffffffff0000002800000000root/usr/local/share/doc/bash/bash.html
BASH(1) Manual Page
BASH(1) | 2014 February 2 | BASH(1)
|
Index
NAME
bash - GNU Bourne-Again SHell
SYNOPSIS
bash
[options]
[command_string | file]
COPYRIGHT
Bash is Copyright © 1989-2013 by the Free Software Foundation, Inc.
DESCRIPTION
Bash
is an sh-compatible command language interpreter that
executes commands read from the standard input or from a file.
Bash
also incorporates useful features from the Korn and C
shells (ksh and csh).
Bash
is intended to be a conformant implementation of the
Shell and Utilities portion of the IEEE POSIX specification
(IEEE Standard 1003.1).
Bash
can be configured to be POSIX-conformant by default.
OPTIONS
All of the single-character shell options documented in the
description of the set builtin command can be used as options
when the shell is invoked.
In addition, bash
interprets the following options when it is invoked:
- -c
-
If the
-c
option is present, then commands are read from the first non-option argument
command_string.
If there are arguments after the
command_string,
they are assigned to the positional parameters, starting with
$0.
- -i
-
If the
-i
option is present, the shell is
interactive.
- -l
-
Make
bash
act as if it had been invoked as a login shell (see
INVOCATION
below).
- -r
-
If the
-r
option is present, the shell becomes
restricted
(see
RESTRICTED SHELL
below).
- -s
-
If the
-s
option is present, or if no arguments remain after option
processing, then commands are read from the standard input.
This option allows the positional parameters to be set
when invoking an interactive shell.
- -D
-
A list of all double-quoted strings preceded by $
is printed on the standard output.
These are the strings that
are subject to language translation when the current locale
is not C or POSIX.
This implies the -n option; no commands will be executed.
- [-+]O [shopt_option]
-
shopt_option is one of the shell options accepted by the
shopt builtin (see
SHELL BUILTIN COMMANDS
below).
If shopt_option is present, -O sets the value of that option;
+O unsets it.
If shopt_option is not supplied, the names and values of the shell
options accepted by shopt are printed on the standard output.
If the invocation option is +O, the output is displayed in a format
that may be reused as input.
- --
-
A
--
signals the end of options and disables further option processing.
Any arguments after the
--
are treated as filenames and arguments. An argument of
-
is equivalent to --.
Bash
also interprets a number of multi-character options.
These options must appear on the command line before the
single-character options to be recognized.
- --debugger
-
Arrange for the debugger profile to be executed before the shell
starts.
Turns on extended debugging mode (see the description of the
extdebug
option to the
shopt
builtin below).
- --dump-po-strings
-
Equivalent to -D, but the output is in the GNU gettext
po (portable object) file format.
- --dump-strings
-
Equivalent to -D.
- --help
-
Display a usage message on standard output and exit successfully.
- --init-file file
-
- --rcfile file
-
Execute commands from
file
instead of the standard personal initialization file
~/.bashrc
if the shell is interactive (see
INVOCATION
below).
- --login
-
Equivalent to -l.
- --noediting
-
Do not use the GNU
readline
library to read command lines when the shell is interactive.
- --noprofile
-
Do not read either the system-wide startup file
/etc/profile
or any of the personal initialization files
~/.bash_profile,
~/.bash_login,
or
~/.profile.
By default,
bash
reads these files when it is invoked as a login shell (see
INVOCATION
below).
- --norc
-
Do not read and execute the personal initialization file
~/.bashrc
if the shell is interactive.
This option is on by default if the shell is invoked as
sh.
- --posix
-
Change the behavior of bash where the default operation differs
from the POSIX standard to match the standard (posix mode).
See
SEE ALSO
below for a reference to a document that details how posix mode affects
bash's behavior.
- --restricted
-
The shell becomes restricted (see
RESTRICTED SHELL
below).
- --verbose
-
Equivalent to -v.
- --version
-
Show version information for this instance of
bash
on the standard output and exit successfully.
ARGUMENTS
If arguments remain after option processing, and neither the
-c
nor the
-s
option has been supplied, the first argument is assumed to
be the name of a file containing shell commands.
If
bash
is invoked in this fashion,
$0
is set to the name of the file, and the positional parameters
are set to the remaining arguments.
Bash
reads and executes commands from this file, then exits.
Bash's exit status is the exit status of the last command
executed in the script.
If no commands are executed, the exit status is 0.
An attempt is first made to open the file in the current directory, and,
if no file is found, then the shell searches the directories in
PATH
for the script.
INVOCATION
A login shell is one whose first character of argument zero is a
-,
or one started with the
--login
option.
An interactive shell is one started without non-option arguments
and without the
-c
option
whose standard input and error are
both connected to terminals (as determined by
isatty(3)),
or one started with the
-i
option.
PS1
is set and
$-
includes
i
if
bash
is interactive,
allowing a shell script or a startup file to test this state.
The following paragraphs describe how
bash
executes its startup files.
If any of the files exist but cannot be read,
bash
reports an error.
Tildes are expanded in filenames as described below under
Tilde Expansion
in the
EXPANSION
section.
When
bash
is invoked as an interactive login shell, or as a non-interactive shell
with the --login option, it first reads and
executes commands from the file /etc/profile, if that
file exists.
After reading that file, it looks for ~/.bash_profile,
~/.bash_login, and ~/.profile, in that order, and reads
and executes commands from the first one that exists and is readable.
The
--noprofile
option may be used when the shell is started to inhibit this behavior.
When a login shell exits,
bash
reads and executes commands from the file ~/.bash_logout, if it
exists.
When an interactive shell that is not a login shell is started,
bash
reads and executes commands from ~/.bashrc, if that file exists.
This may be inhibited by using the
--norc
option.
The --rcfile file option will force
bash
to read and execute commands from file instead of ~/.bashrc.
When
bash
is started non-interactively, to run a shell script, for example, it
looks for the variable
BASH_ENV
in the environment, expands its value if it appears there, and uses the
expanded value as the name of a file to read and execute.
Bash
behaves as if the following command were executed:
-
if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
but the value of the
PATH
variable is not used to search for the filename.
If
bash
is invoked with the name
sh,
it tries to mimic the startup behavior of historical versions of
sh
as closely as possible,
while conforming to the POSIX standard as well.
When invoked as an interactive login shell, or a non-interactive
shell with the --login option, it first attempts to
read and execute commands from
/etc/profile
and
~/.profile,
in that order.
The
--noprofile
option may be used to inhibit this behavior.
When invoked as an interactive shell with the name
sh,
bash
looks for the variable
ENV,
expands its value if it is defined, and uses the
expanded value as the name of a file to read and execute.
Since a shell invoked as
sh
does not attempt to read and execute commands from any other startup
files, the
--rcfile
option has no effect.
A non-interactive shell invoked with the name
sh
does not attempt to read any other startup files.
When invoked as
sh,
bash
enters
posix
mode after the startup files are read.
When
bash
is started in
posix
mode, as with the
--posix
command line option, it follows the POSIX standard for startup files.
In this mode, interactive shells expand the
ENV
variable and commands are read and executed from the file
whose name is the expanded value.
No other startup files are read.
Bash
attempts to determine when it is being run with its standard input
connected to a network connection, as when executed by the remote shell
daemon, usually rshd, or the secure shell daemon sshd.
If
bash
determines it is being run in this fashion, it reads and executes
commands from ~/.bashrc, if that file exists and is readable.
It will not do this if invoked as sh.
The
--norc
option may be used to inhibit this behavior, and the
--rcfile
option may be used to force another file to be read, but neither
rshd nor sshd generally invoke the shell with those options
or allow them to be specified.
If the shell is started with the effective user (group) id not equal to the
real user (group) id, and the -p option is not supplied, no startup
files are read, shell functions are not inherited from the environment, the
SHELLOPTS,
BASHOPTS,
CDPATH,
and
GLOBIGNORE
variables, if they appear in the environment, are ignored,
and the effective user id is set to the real user id.
If the -p option is supplied at invocation, the startup behavior is
the same, but the effective user id is not reset.
DEFINITIONS
The following definitions are used throughout the rest of this
document.
- blank
-
A space or tab.
- word
-
A sequence of characters considered as a single unit by the shell.
Also known as a
token.
- name
-
A
word
consisting only of alphanumeric characters and underscores, and
beginning with an alphabetic character or an underscore. Also
referred to as an
identifier.
- metacharacter
-
A character that, when unquoted, separates words. One of the following:
-
| & ; ( ) < > space tab
- control operator
-
A token that performs a control function. It is one of the following
symbols:
-
|| & && ; ;; ( ) | |& <newline>
RESERVED WORDS
Reserved words are words that have a special meaning to the shell.
The following words are recognized as reserved when unquoted and either
the first word of a simple command (see
SHELL GRAMMAR
below) or the third word of a
case
or
for
command:
-
! case coproc do done elif else esac fi for function if in select then until while { } time [[ ]]
SHELL GRAMMAR
Simple Commands
A simple command is a sequence of optional variable assignments
followed by blank-separated words and redirections, and
terminated by a control operator. The first word
specifies the command to be executed, and is passed as argument zero.
The remaining words are passed as arguments to the invoked command.
The return value of a simple command is its exit status, or
128+n if the command is terminated by signal
n.
Pipelines
A pipeline is a sequence of one or more commands separated by
one of the control operators
|
or |&.
The format for a pipeline is:
-
[time [-p]] [ ! ] command [ [|||&] command2 ... ]
The standard output of
command
is connected via a pipe to the standard input of
command2.
This connection is performed before any redirections specified by the
command (see
REDIRECTION
below).
If |& is used, command's standard error, in addition to its
standard output, is connected to
command2's standard input through the pipe;
it is shorthand for 2>&1 |.
This implicit redirection of the standard error to the standard output is
performed after any redirections specified by the command.
The return status of a pipeline is the exit status of the last
command, unless the pipefail option is enabled.
If pipefail is enabled, the pipeline's return status is the
value of the last (rightmost) command to exit with a non-zero status,
or zero if all commands exit successfully.
If the reserved word
!
precedes a pipeline, the exit status of that pipeline is the logical
negation of the exit status as described above.
The shell waits for all commands in the pipeline to
terminate before returning a value.
If the
time
reserved word precedes a pipeline, the elapsed as well as user and
system time consumed by its execution are reported when the pipeline
terminates.
The -p option changes the output format to that specified by POSIX.
When the shell is in posix mode, it does not recognize
time as a reserved word if the next token begins with a `-'.
The
TIMEFORMAT
variable may be set to a format string that specifies how the timing
information should be displayed; see the description of
TIMEFORMAT
under
Shell Variables
below.
When the shell is in posix mode, time
may be followed by a newline. In this case, the shell displays the
total user and system time consumed by the shell and its children.
The
TIMEFORMAT
variable may be used to specify the format of
the time information.
Each command in a pipeline is executed as a separate process (i.e., in a
subshell).
Lists
A list is a sequence of one or more pipelines separated by one
of the operators
;,
&,
&&,
or
||,
and optionally terminated by one of
;,
&,
or
<newline>.
Of these list operators,
&&
and
||
have equal precedence, followed by
;
and
&,
which have equal precedence.
A sequence of one or more newlines may appear in a list instead
of a semicolon to delimit commands.
If a command is terminated by the control operator
&,
the shell executes the command in the background
in a subshell. The shell does not wait for the command to
finish, and the return status is 0. Commands separated by a
;
are executed sequentially; the shell waits for each
command to terminate in turn. The return status is the
exit status of the last command executed.
AND and OR lists are sequences of one of more pipelines separated by the
&& and || control operators, respectively.
AND and OR lists are executed with left associativity.
An AND list has the form
-
command1 && command2
command2
is executed if, and only if,
command1
returns an exit status of zero.
An OR list has the form
-
command1 || command2
command2
is executed if and only if
command1
returns a non-zero exit status.
The return status of
AND and OR lists is the exit status of the last command
executed in the list.
Compound Commands
A compound command is one of the following.
In most cases a list in a command's description may be separated from
the rest of the command by one or more newlines, and may be followed by a
newline in place of a semicolon.
- (list)
-
list is executed in a subshell environment (see
COMMAND EXECUTION ENVIRONMENT
below).
Variable assignments and builtin
commands that affect the shell's environment do not remain in effect
after the command completes. The return status is the exit status of
list.
- { list; }
-
list is simply executed in the current shell environment.
list must be terminated with a newline or semicolon.
This is known as a group command.
The return status is the exit status of
list.
Note that unlike the metacharacters ( and ), { and
} are reserved words and must occur where a reserved
word is permitted to be recognized. Since they do not cause a word
break, they must be separated from list by whitespace or another
shell metacharacter.
- ((expression))
-
The expression is evaluated according to the rules described
below under
ARITHMETIC EVALUATION.
If the value of the expression is non-zero, the return status is 0;
otherwise the return status is 1. This is exactly equivalent to
let "expression".
- [[ expression ]]
-
Return a status of 0 or 1 depending on the evaluation of
the conditional expression expression.
Expressions are composed of the primaries described below under
CONDITIONAL EXPRESSIONS.
Word splitting and pathname expansion are not performed on the words
between the [[ and ]]; tilde expansion,
parameter and variable expansion,
arithmetic expansion, command substitution, process
substitution, and quote removal are performed.
Conditional operators such as -f must be unquoted to be recognized
as primaries.
When used with [[, the < and > operators sort
lexicographically using the current locale.
When the == and != operators are used, the string to the
right of the operator is considered a pattern and matched according
to the rules described below under Pattern Matching,
as if the extglob shell option were enabled.
The = operator is equivalent to ==.
If the shell option
nocasematch
is enabled, the match is performed without regard to the case
of alphabetic characters.
The return value is 0 if the string matches (==) or does not match
(!=) the pattern, and 1 otherwise.
Any part of the pattern may be quoted to force the quoted portion
to be matched as a string.
An additional binary operator, =~, is available, with the same
precedence as == and !=.
When it is used, the string to the right of the operator is considered
an extended regular expression and matched accordingly (as in regex(3)).
The return value is 0 if the string matches
the pattern, and 1 otherwise.
If the regular expression is syntactically incorrect, the conditional
expression's return value is 2.
If the shell option
nocasematch
is enabled, the match is performed without regard to the case
of alphabetic characters.
Any part of the pattern may be quoted to force the quoted portion
to be matched as a string.
Bracket expressions in regular expressions must be treated carefully,
since normal quoting characters lose their meanings between brackets.
If the pattern is stored in a shell variable, quoting the variable
expansion forces the entire pattern to be matched as a string.
Substrings matched by parenthesized subexpressions within the regular
expression are saved in the array variable
BASH_REMATCH.
The element of
BASH_REMATCH
with index 0 is the portion of the string
matching the entire regular expression.
The element of
BASH_REMATCH
with index n is the portion of the
string matching the nth parenthesized subexpression.
Expressions may be combined using the following operators, listed
in decreasing order of precedence:
-
- ( expression )
-
Returns the value of expression.
This may be used to override the normal precedence of operators.
- ! expression
-
True if
expression
is false.
- expression1 && expression2
-
True if both
expression1
and
expression2
are true.
- expression1 || expression2
-
True if either
expression1
or
expression2
is true.
The && and ||
operators do not evaluate expression2 if the value of
expression1 is sufficient to determine the return value of
the entire conditional expression.
- for name [ [ in [ word ... ] ] ; ] do list ; done
-
The list of words following in is expanded, generating a list
of items.
The variable name is set to each element of this list
in turn, and list is executed each time.
If the in word is omitted, the for command executes
list once for each positional parameter that is set (see
PARAMETERS
below).
The return status is the exit status of the last command that executes.
If the expansion of the items following in results in an empty
list, no commands are executed, and the return status is 0.
- for (( expr1 ; expr2 ; expr3 )) ; do list ; done
-
First, the arithmetic expression expr1 is evaluated according
to the rules described below under
ARITHMETIC EVALUATION.
The arithmetic expression expr2 is then evaluated repeatedly
until it evaluates to zero.
Each time expr2 evaluates to a non-zero value, list is
executed and the arithmetic expression expr3 is evaluated.
If any expression is omitted, it behaves as if it evaluates to 1.
The return value is the exit status of the last command in list
that is executed, or false if any of the expressions is invalid.
- select name [ in word ] ; do list ; done
-
The list of words following in is expanded, generating a list
of items. The set of expanded words is printed on the standard
error, each preceded by a number. If the in
word is omitted, the positional parameters are printed (see
PARAMETERS
below). The
PS3
prompt is then displayed and a line read from the standard input.
If the line consists of a number corresponding to one of
the displayed words, then the value of
name
is set to that word. If the line is empty, the words and prompt
are displayed again. If EOF is read, the command completes. Any
other value read causes
name
to be set to null. The line read is saved in the variable
REPLY.
The
list
is executed after each selection until a
break
command is executed.
The exit status of
select
is the exit status of the last command executed in
list,
or zero if no commands were executed.
- case word in [ [(] pattern [ | pattern ]
-
A case command first expands word, and tries to match
it against each pattern in turn, using the same matching rules
as for pathname expansion (see
Pathname Expansion
below).
The word is expanded using tilde
expansion, parameter and variable expansion, arithmetic substitution,
command substitution, process substitution and quote removal.
Each pattern examined is expanded using tilde
expansion, parameter and variable expansion, arithmetic substitution,
command substitution, and process substitution.
If the shell option
nocasematch
is enabled, the match is performed without regard to the case
of alphabetic characters.
When a match is found, the corresponding list is executed.
If the ;; operator is used, no subsequent matches are attempted after
the first pattern match.
Using ;& in place of ;; causes execution to continue with
the list associated with the next set of patterns.
Using ;;& in place of ;; causes the shell to test the next
pattern list in the statement, if any, and execute any associated list
on a successful match.
The exit status is zero if no
pattern matches. Otherwise, it is the exit status of the
last command executed in list.
- if list; then list; [ elif list; then list; ] ... [ else list; ] fi
-
The
if
list
is executed. If its exit status is zero, the
then list is executed. Otherwise, each elif
list is executed in turn, and if its exit status is zero,
the corresponding then list is executed and the
command completes. Otherwise, the else list is
executed, if present. The exit status is the exit status of the
last command executed, or zero if no condition tested true.
- while list-1; do list-2; done
-
- until list-1; do list-2; done
-
The while command continuously executes the list
list-2 as long as the last command in the list list-1 returns
an exit status of zero. The until command is identical
to the while command, except that the test is negated;
list-2
is executed as long as the last command in
list-1
returns a non-zero exit status.
The exit status of the while and until commands
is the exit status
of the last command executed in list-2, or zero if
none was executed.
Coprocesses
A coprocess is a shell command preceded by the coproc reserved
word.
A coprocess is executed asynchronously in a subshell, as if the command
had been terminated with the & control operator, with a two-way pipe
established between the executing shell and the coprocess.
The format for a coprocess is:
-
coproc [NAME] command [redirections]
This creates a coprocess named NAME.
If NAME is not supplied, the default name is COPROC.
NAME must not be supplied if command is a simple
command (see above); otherwise, it is interpreted as the first word
of the simple command.
When the coprocess is executed, the shell creates an array variable (see
Arrays
below) named NAME in the context of the executing shell.
The standard output of
command
is connected via a pipe to a file descriptor in the executing shell,
and that file descriptor is assigned to NAME[0].
The standard input of
command
is connected via a pipe to a file descriptor in the executing shell,
and that file descriptor is assigned to NAME[1].
This pipe is established before any redirections specified by the
command (see
REDIRECTION
below).
The file descriptors can be utilized as arguments to shell commands
and redirections using standard word expansions.
The file descriptors are not available in subshells.
The process ID of the shell spawned to execute the coprocess is
available as the value of the variable NAME_PID.
The wait
builtin command may be used to wait for the coprocess to terminate.
Since the coprocess is created as an asynchronous command,
the coproc command always returns success.
The return status of a coprocess is the exit status of command.
Shell Function Definitions
A shell function is an object that is called like a simple command and
executes a compound command with a new set of positional parameters.
Shell functions are declared as follows:
- name () compound-command [redirection]
-
- function name [()] compound-command [redirection]
-
This defines a function named name.
The reserved word function is optional.
If the function reserved word is supplied, the parentheses are optional.
The body of the function is the compound command
compound-command
(see Compound Commands above).
That command is usually a list of commands between { and }, but
may be any command listed under Compound Commands above.
compound-command is executed whenever name is specified as the
name of a simple command.
When in posix mode, name may not be the name of one of the
POSIX special builtins.
Any redirections (see
REDIRECTION
below) specified when a function is defined are performed
when the function is executed.
The exit status of a function definition is zero unless a syntax error
occurs or a readonly function with the same name already exists.
When executed, the exit status of a function is the exit status of the
last command executed in the body. (See
FUNCTIONS
below.)
COMMENTS
In a non-interactive shell, or an interactive shell in which the
interactive_comments
option to the
shopt
builtin is enabled (see
SHELL BUILTIN COMMANDS
below), a word beginning with
#
causes that word and all remaining characters on that line to
be ignored. An interactive shell without the
interactive_comments
option enabled does not allow comments. The
interactive_comments
option is on by default in interactive shells.
QUOTING
Quoting is used to remove the special meaning of certain
characters or words to the shell. Quoting can be used to
disable special treatment for special characters, to prevent
reserved words from being recognized as such, and to prevent
parameter expansion.
Each of the metacharacters listed above under
DEFINITIONS
has special meaning to the shell and must be quoted if it is to
represent itself.
When the command history expansion facilities are being used
(see
HISTORY EXPANSION
below), the
history expansion character, usually !, must be quoted
to prevent history expansion.
There are three quoting mechanisms: the
escape character,
single quotes, and double quotes.
A non-quoted backslash (\) is the
escape character.
It preserves the literal value of the next character that follows,
with the exception of <newline>. If a \<newline> pair
appears, and the backslash is not itself quoted, the \<newline>
is treated as a line continuation (that is, it is removed from the
input stream and effectively ignored).
Enclosing characters in single quotes preserves the literal value
of each character within the quotes. A single quote may not occur
between single quotes, even when preceded by a backslash.
Enclosing characters in double quotes preserves the literal value
of all characters within the quotes, with the exception of
$,
`,
\,
and, when history expansion is enabled,
!.
The characters
$
and
`
retain their special meaning within double quotes. The backslash
retains its special meaning only when followed by one of the following
characters:
$,
`,
",
\,
or
<newline>.
A double quote may be quoted within double quotes by preceding it with
a backslash.
If enabled, history expansion will be performed unless an
!
appearing in double quotes is escaped using a backslash.
The backslash preceding the
!
is not removed.
The special parameters
*
and
@
have special meaning when in double
quotes (see
PARAMETERS
below).
Words of the form $aqstringaq are treated specially. The
word expands to string, with backslash-escaped characters replaced
as specified by the ANSI C standard. Backslash escape sequences, if
present, are decoded as follows:
-
- \a
-
alert (bell)
- \b
-
backspace
- \e
-
- \E
-
an escape character
- \f
-
form feed
- \n
-
new line
- \r
-
carriage return
- \t
-
horizontal tab
- \v
-
vertical tab
- \\
-
backslash
- \aq
-
single quote
- \dq
-
double quote
- \nnn
-
the eight-bit character whose value is the octal value nnn
(one to three digits)
- \xHH
-
the eight-bit character whose value is the hexadecimal value HH
(one or two hex digits)
- \uHHHH
-
the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
HHHH (one to four hex digits)
- \UHHHHHHHH
-
the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
HHHHHHHH (one to eight hex digits)
- \cx
-
a control-x character
The expanded result is single-quoted, as if the dollar sign had
not been present.
A double-quoted string preceded by a dollar sign ($dqstringdq)
will cause the string to be translated according to the current locale.
If the current locale is C or POSIX, the dollar sign
is ignored.
If the string is translated and replaced, the replacement is
double-quoted.
PARAMETERS
A
parameter
is an entity that stores values.
It can be a
name,
a number, or one of the special characters listed below under
Special Parameters.
A
variable
is a parameter denoted by a
name.
A variable has a value and zero or more attributes.
Attributes are assigned using the
declare
builtin command (see
declare
below in
SHELL BUILTIN COMMANDS).
A parameter is set if it has been assigned a value. The null string is
a valid value. Once a variable is set, it may be unset only by using
the
unset
builtin command (see
SHELL BUILTIN COMMANDS
below).
A
variable
may be assigned to by a statement of the form
-
name=[value]
If
value
is not given, the variable is assigned the null string. All
values
undergo tilde expansion, parameter and variable expansion,
command substitution, arithmetic expansion, and quote
removal (see
EXPANSION
below). If the variable has its
integer
attribute set, then
value
is evaluated as an arithmetic expression even if the $((...)) expansion is
not used (see
Arithmetic Expansion
below).
Word splitting is not performed, with the exception
of "$@" as explained below under
Special Parameters.
Pathname expansion is not performed.
Assignment statements may also appear as arguments to the
alias,
declare,
typeset,
export,
readonly,
and
local
builtin commands.
When in posix mode, these builtins may appear in a command after
one or more instances of the command builtin and retain these
assignment statement properties.
In the context where an assignment statement is assigning a value
to a shell variable or array index, the += operator can be used to
append to or add to the variable's previous value.
When += is applied to a variable for which the integer attribute has been
set, value is evaluated as an arithmetic expression and added to the
variable's current value, which is also evaluated.
When += is applied to an array variable using compound assignment (see
Arrays
below), the
variable's value is not unset (as it is when using =), and new values are
appended to the array beginning at one greater than the array's maximum index
(for indexed arrays) or added as additional key-value pairs in an
associative array.
When applied to a string-valued variable, value is expanded and
appended to the variable's value.
A variable can be assigned the nameref attribute using the
-n option to the declare or local builtin commands
(see the descriptions of declare and local below)
to create a nameref, or a reference to another variable.
This allows variables to be manipulated indirectly.
Whenever the nameref variable is referenced or assigned to, the operation
is actually performed on the variable specified by the nameref variable's
value.
A nameref is commonly used within shell functions to refer to a variable
whose name is passed as an argument to the function.
For instance, if a variable name is passed to a shell function as its first
argument, running
-
declare -n ref=$1
inside the function creates a nameref variable ref whose value is
the variable name passed as the first argument.
References and assignments to ref are treated as references and
assignments to the variable whose name was passed as $1.
If the control variable in a for loop has the nameref attribute,
the list of words can be a list of shell variables, and a name reference
will be established for each word in the list, in turn, when the loop is
executed.
Array variables cannot be given the -n attribute.
However, nameref variables can reference array variables and subscripted
array variables.
Namerefs can be unset using the -n option to the unset builtin.
Otherwise, if unset is executed with the name of a nameref variable
as an argument, the variable referenced by the nameref variable will be unset.
Positional Parameters
A
positional parameter
is a parameter denoted by one or more
digits, other than the single digit 0. Positional parameters are
assigned from the shell's arguments when it is invoked,
and may be reassigned using the
set
builtin command. Positional parameters may not be assigned to
with assignment statements. The positional parameters are
temporarily replaced when a shell function is executed (see
FUNCTIONS
below).
When a positional parameter consisting of more than a single
digit is expanded, it must be enclosed in braces (see
EXPANSION
below).
Special Parameters
The shell treats several parameters specially. These parameters may
only be referenced; assignment to them is not allowed.
- *
-
Expands to the positional parameters, starting from one.
When the expansion is not within double quotes, each positional parameter
expands to a separate word.
In contexts where it is performed, those words
are subject to further word splitting and pathname expansion.
When the expansion occurs within double quotes, it expands to a single word
with the value of each parameter separated by the first character
of the
IFS
special variable. That is, "$*" is equivalent
to "$1c$2c...", where
c
is the first character of the value of the
IFS
variable. If
IFS
is unset, the parameters are separated by spaces.
If
IFS
is null, the parameters are joined without intervening separators.
- @
-
Expands to the positional parameters, starting from one. When the
expansion occurs within double quotes, each parameter expands to a
separate word. That is, "$@" is equivalent to
"$1" "$2" ...
If the double-quoted expansion occurs within a word, the expansion of
the first parameter is joined with the beginning part of the original
word, and the expansion of the last parameter is joined with the last
part of the original word.
When there are no positional parameters, "$@" and
$@
expand to nothing (i.e., they are removed).
- #
-
Expands to the number of positional parameters in decimal.
- ?
-
Expands to the exit status of the most recently executed foreground
pipeline.
- -
-
Expands to the current option flags as specified upon invocation,
by the
set
builtin command, or those set by the shell itself
(such as the
-i
option).
- $
-
Expands to the process ID of the shell. In a () subshell, it
expands to the process ID of the current shell, not the
subshell.
- !
-
Expands to the process ID of the job most recently placed into the
background, whether executed as an asynchronous command or using
the bg builtin (see
JOB CONTROL
below).
- 0
-
Expands to the name of the shell or shell script. This is set at
shell initialization. If
bash
is invoked with a file of commands,
$0
is set to the name of that file. If
bash
is started with the
-c
option, then
$0
is set to the first argument after the string to be
executed, if one is present. Otherwise, it is set
to the filename used to invoke
bash,
as given by argument zero.
- _
-
At shell startup, set to the absolute pathname used to invoke the
shell or shell script being executed as passed in the environment
or argument list.
Subsequently, expands to the last argument to the previous command,
after expansion.
Also set to the full pathname used to invoke each command executed
and placed in the environment exported to that command.
When checking mail, this parameter holds the name of the mail file
currently being checked.
Shell Variables
The following variables are set by the shell:
- BASH
-
Expands to the full filename used to invoke this instance of
bash.
- BASHOPTS
-
A colon-separated list of enabled shell options. Each word in
the list is a valid argument for the
-s
option to the
shopt
builtin command (see
SHELL BUILTIN COMMANDS
below). The options appearing in
BASHOPTS
are those reported as
on
by shopt.
If this variable is in the environment when
bash
starts up, each shell option in the list will be enabled before
reading any startup files.
This variable is read-only.
- BASHPID
-
Expands to the process ID of the current bash process.
This differs from $$ under certain circumstances, such as subshells
that do not require bash to be re-initialized.
- BASH_ALIASES
-
An associative array variable whose members correspond to the internal
list of aliases as maintained by the alias builtin.
Elements added to this array appear in the alias list; unsetting array
elements cause aliases to be removed from the alias list.
- BASH_ARGC
-
An array variable whose values are the number of parameters in each
frame of the current bash execution call stack.
The number of
parameters to the current subroutine (shell function or script executed
with . or source) is at the top of the stack.
When a subroutine is executed, the number of parameters passed is pushed onto
BASH_ARGC.
The shell sets
BASH_ARGC
only when in extended debugging mode (see the description of the
extdebug
option to the
shopt
builtin below)
- BASH_ARGV
-
An array variable containing all of the parameters in the current bash
execution call stack. The final parameter of the last subroutine call
is at the top of the stack; the first parameter of the initial call is
at the bottom. When a subroutine is executed, the parameters supplied
are pushed onto
BASH_ARGV.
The shell sets
BASH_ARGV
only when in extended debugging mode
(see the description of the
extdebug
option to the
shopt
builtin below)
- BASH_CMDS
-
An associative array variable whose members correspond to the internal
hash table of commands as maintained by the hash builtin.
Elements added to this array appear in the hash table; unsetting array
elements cause commands to be removed from the hash table.
- BASH_COMMAND
-
The command currently being executed or about to be executed, unless the
shell is executing a command as the result of a trap,
in which case it is the command executing at the time of the trap.
- BASH_EXECUTION_STRING
-
The command argument to the -c invocation option.
- BASH_LINENO
-
An array variable whose members are the line numbers in source files
where each corresponding member of
FUNCNAME
was invoked.
${BASH_LINENO[$i]} is the line number in the source
file (${BASH_SOURCE[$i+1]}) where
${FUNCNAME[$i]} was called
(or ${BASH_LINENO[$i-1]} if referenced within another
shell function).
Use
LINENO
to obtain the current line number.
- BASH_REMATCH
-
An array variable whose members are assigned by the =~ binary
operator to the [[ conditional command.
The element with index 0 is the portion of the string
matching the entire regular expression.
The element with index n is the portion of the
string matching the nth parenthesized subexpression.
This variable is read-only.
- BASH_SOURCE
-
An array variable whose members are the source filenames
where the corresponding shell function names in the
FUNCNAME
array variable are defined.
The shell function
${FUNCNAME[$i]} is defined in the file
${BASH_SOURCE[$i]} and called from
${BASH_SOURCE[$i+1]}.
- BASH_SUBSHELL
-
Incremented by one within each subshell or subshell environment when
the shell begins executing in that environment.
The initial value is 0.
- BASH_VERSINFO
-
A readonly array variable whose members hold version information for
this instance of
bash.
The values assigned to the array members are as follows:
-
- BASH_VERSINFO[0]
-
The major version number (the release).
- BASH_VERSINFO[1]
-
The minor version number (the version).
- BASH_VERSINFO[2]
-
The patch level.
- BASH_VERSINFO[3]
-
The build version.
- BASH_VERSINFO[4]
-
The release status (e.g., beta1).
- BASH_VERSINFO[5]
-
The value of
MACHTYPE.
- BASH_VERSION
-
Expands to a string describing the version of this instance of
bash.
- COMP_CWORD
-
An index into ${COMP_WORDS} of the word containing the current
cursor position.
This variable is available only in shell functions invoked by the
programmable completion facilities (see Programmable Completion
below).
- COMP_KEY
-
The key (or final key of a key sequence) used to invoke the current
completion function.
- COMP_LINE
-
The current command line.
This variable is available only in shell functions and external
commands invoked by the
programmable completion facilities (see Programmable Completion
below).
- COMP_POINT
-
The index of the current cursor position relative to the beginning of
the current command.
If the current cursor position is at the end of the current command,
the value of this variable is equal to ${#COMP_LINE}.
This variable is available only in shell functions and external
commands invoked by the
programmable completion facilities (see Programmable Completion
below).
- COMP_TYPE
-
Set to an integer value corresponding to the type of completion attempted
that caused a completion function to be called:
TAB, for normal completion,
?, for listing completions after successive tabs,
!, for listing alternatives on partial word completion,
@, to list completions if the word is not unmodified,
or
%, for menu completion.
This variable is available only in shell functions and external
commands invoked by the
programmable completion facilities (see Programmable Completion
below).
- COMP_WORDBREAKS
-
The set of characters that the readline library treats as word
separators when performing word completion.
If
COMP_WORDBREAKS
is unset, it loses its special properties, even if it is
subsequently reset.
- COMP_WORDS
-
An array variable (see Arrays below) consisting of the individual
words in the current command line.
The line is split into words as readline would split it, using
COMP_WORDBREAKS
as described above.
This variable is available only in shell functions invoked by the
programmable completion facilities (see Programmable Completion
below).
- COPROC
-
An array variable (see Arrays below) created to hold the file descriptors
for output from and input to an unnamed coprocess (see Coprocesses
above).
- DIRSTACK
-
An array variable (see
Arrays
below) containing the current contents of the directory stack.
Directories appear in the stack in the order they are displayed by the
dirs
builtin.
Assigning to members of this array variable may be used to modify
directories already in the stack, but the
pushd
and
popd
builtins must be used to add and remove directories.
Assignment to this variable will not change the current directory.
If
DIRSTACK
is unset, it loses its special properties, even if it is
subsequently reset.
- EUID
-
Expands to the effective user ID of the current user, initialized at
shell startup. This variable is readonly.
- FUNCNAME
-
An array variable containing the names of all shell functions
currently in the execution call stack.
The element with index 0 is the name of any currently-executing
shell function.
The bottom-most element (the one with the highest index) is
"main".
This variable exists only when a shell function is executing.
Assignments to
FUNCNAME
have no effect and return an error status.
If
FUNCNAME
is unset, it loses its special properties, even if it is
subsequently reset.
This variable can be used with BASH_LINENO and BASH_SOURCE.
Each element of FUNCNAME has corresponding elements in
BASH_LINENO and BASH_SOURCE to describe the call stack.
For instance, ${FUNCNAME[$i]} was called from the file
${BASH_SOURCE[$i+1]} at line number
${BASH_LINENO[$i]}.
The caller builtin displays the current call stack using this
information.
- GROUPS
-
An array variable containing the list of groups of which the current
user is a member.
Assignments to
GROUPS
have no effect and return an error status.
If
GROUPS
is unset, it loses its special properties, even if it is
subsequently reset.
- HISTCMD
-
The history number, or index in the history list, of the current
command.
If
HISTCMD
is unset, it loses its special properties, even if it is
subsequently reset.
- HOSTNAME
-
Automatically set to the name of the current host.
- HOSTTYPE
-
Automatically set to a string that uniquely
describes the type of machine on which
bash
is executing.
The default is system-dependent.
- LINENO
-
Each time this parameter is referenced, the shell substitutes
a decimal number representing the current sequential line number
(starting with 1) within a script or function. When not in a
script or function, the value substituted is not guaranteed to
be meaningful.
If
LINENO
is unset, it loses its special properties, even if it is
subsequently reset.
- MACHTYPE
-
Automatically set to a string that fully describes the system
type on which
bash
is executing, in the standard GNU cpu-company-system format.
The default is system-dependent.
- MAPFILE
-
An array variable (see Arrays below) created to hold the text
read by the mapfile builtin when no variable name is supplied.
- OLDPWD
-
The previous working directory as set by the
cd
command.
- OPTARG
-
The value of the last option argument processed by the
getopts
builtin command (see
SHELL BUILTIN COMMANDS
below).
- OPTIND
-
The index of the next argument to be processed by the
getopts
builtin command (see
SHELL BUILTIN COMMANDS
below).
- OSTYPE
-
Automatically set to a string that
describes the operating system on which
bash
is executing.
The default is system-dependent.
- PIPESTATUS
-
An array variable (see
Arrays
below) containing a list of exit status values from the processes
in the most-recently-executed foreground pipeline (which may
contain only a single command).
- PPID
-
The process ID of the shell's parent. This variable is readonly.
- PWD
-
The current working directory as set by the
cd
command.
- RANDOM
-
Each time this parameter is referenced, a random integer between
0 and 32767 is
generated. The sequence of random numbers may be initialized by assigning
a value to
RANDOM.
If
RANDOM
is unset, it loses its special properties, even if it is
subsequently reset.
- READLINE_LINE
-
The contents of the
readline
line buffer, for use with
bind -x
(see
SHELL BUILTIN COMMANDS
below).
- READLINE_POINT
-
The position of the insertion point in the
readline
line buffer, for use with
bind -x
(see
SHELL BUILTIN COMMANDS
below).
- REPLY
-
Set to the line of input read by the
read
builtin command when no arguments are supplied.
- SECONDS
-
Each time this parameter is
referenced, the number of seconds since shell invocation is returned. If a
value is assigned to
SECONDS,
the value returned upon subsequent
references is
the number of seconds since the assignment plus the value assigned.
If
SECONDS
is unset, it loses its special properties, even if it is
subsequently reset.
- SHELLOPTS
-
A colon-separated list of enabled shell options. Each word in
the list is a valid argument for the
-o
option to the
set
builtin command (see
SHELL BUILTIN COMMANDS
below). The options appearing in
SHELLOPTS
are those reported as
on
by set -o.
If this variable is in the environment when
bash
starts up, each shell option in the list will be enabled before
reading any startup files.
This variable is read-only.
- SHLVL
-
Incremented by one each time an instance of
bash
is started.
- UID
-
Expands to the user ID of the current user, initialized at shell startup.
This variable is readonly.
The following variables are used by the shell. In some cases,
bash
assigns a default value to a variable; these cases are noted
below.
- BASH_COMPAT
-
The value is used to set the shell's compatibility level.
See the description of the shopt builtin below under
SHELL BUILTIN COMMANDS
for a description of the various compatibility
levels and their effects.
The value may be a decimal number (e.g., 4.2) or an integer (e.g., 42)
corresponding to the desired compatibility level.
If BASH_COMPAT is unset or set to the empty string, the compatibility
level is set to the default for the current version.
If BASH_COMPAT is set to a value that is not one of the valid
compatibility levels, the shell prints an error message and sets the
compatibility level to the default for the current version.
The valid compatibility levels correspond to the compatibility options
accepted by the shopt builtin described below (for example,
compat42 means that 4.2 and 42 are valid values).
The current version is also a valid value.
- BASH_ENV
-
If this parameter is set when bash is executing a shell script,
its value is interpreted as a filename containing commands to
initialize the shell, as in
~/.bashrc.
The value of
BASH_ENV
is subjected to parameter expansion, command substitution, and arithmetic
expansion before being interpreted as a filename.
PATH
is not used to search for the resultant filename.
- BASH_XTRACEFD
-
If set to an integer corresponding to a valid file descriptor, bash
will write the trace output generated when
set -x
is enabled to that file descriptor.
The file descriptor is closed when
BASH_XTRACEFD
is unset or assigned a new value.
Unsetting
BASH_XTRACEFD
or assigning it the empty string causes the
trace output to be sent to the standard error.
Note that setting
BASH_XTRACEFD
to 2 (the standard error file
descriptor) and then unsetting it will result in the standard error
being closed.
- CDPATH
-
The search path for the
cd
command.
This is a colon-separated list of directories in which the shell looks
for destination directories specified by the
cd
command.
A sample value is
".:~:/usr".
- CHILD_MAX
-
Set the number of exited child status values for the shell to remember.
Bash will not allow this value to be decreased below a POSIX-mandated
minimum, and there is a maximum value (currently 8192) that this may
not exceed.
The minimum value is system-dependent.
- COLUMNS
-
Used by the select compound command to determine the terminal width
when printing selection lists.
Automatically set if the
checkwinsize
option is enabled or in an interactive shell upon receipt of a
SIGWINCH.
- COMPREPLY
-
An array variable from which bash reads the possible completions
generated by a shell function invoked by the programmable completion
facility (see Programmable Completion below).
Each array element contains one possible completion.
- EMACS
-
If bash finds this variable in the environment when the shell starts
with value
t,
it assumes that the shell is running in an Emacs shell buffer and disables
line editing.
- ENV
-
Similar to
BASH_ENV;
used when the shell is invoked in POSIX mode.
- FCEDIT
-
The default editor for the
fc
builtin command.
- FIGNORE
-
A colon-separated list of suffixes to ignore when performing
filename completion (see
READLINE
below).
A filename whose suffix matches one of the entries in
FIGNORE
is excluded from the list of matched filenames.
A sample value is
".o:~".
- FUNCNEST
-
If set to a numeric value greater than 0, defines a maximum function
nesting level. Function invocations that exceed this nesting level
will cause the current command to abort.
- GLOBIGNORE
-
A colon-separated list of patterns defining the set of filenames to
be ignored by pathname expansion.
If a filename matched by a pathname expansion pattern also matches one
of the patterns in
GLOBIGNORE,
it is removed from the list of matches.
- HISTCONTROL
-
A colon-separated list of values controlling how commands are saved on
the history list.
If the list of values includes
ignorespace,
lines which begin with a
space
character are not saved in the history list.
A value of
ignoredups
causes lines matching the previous history entry to not be saved.
A value of
ignoreboth
is shorthand for ignorespace and ignoredups.
A value of
erasedups
causes all previous lines matching the current line to be removed from
the history list before that line is saved.
Any value not in the above list is ignored.
If
HISTCONTROL
is unset, or does not include a valid value,
all lines read by the shell parser are saved on the history list,
subject to the value of
HISTIGNORE.
The second and subsequent lines of a multi-line compound command are
not tested, and are added to the history regardless of the value of
HISTCONTROL.
- HISTFILE
-
The name of the file in which command history is saved (see
HISTORY
below). The default value is ~/.bash_history. If unset, the
command history is not saved when a shell exits.
- HISTFILESIZE
-
The maximum number of lines contained in the history file. When this
variable is assigned a value, the history file is truncated, if
necessary,
to contain no more than that number of lines by removing the oldest entries.
The history file is also truncated to this size after
writing it when a shell exits.
If the value is 0, the history file is truncated to zero size.
Non-numeric values and numeric values less than zero inhibit truncation.
The shell sets the default value to the value of HISTSIZE
after reading any startup files.
- HISTIGNORE
-
A colon-separated list of patterns used to decide which command lines
should be saved on the history list. Each pattern is anchored at the
beginning of the line and must match the complete line (no implicit
`*' is appended). Each pattern is tested against the line
after the checks specified by
HISTCONTROL
are applied.
In addition to the normal shell pattern matching characters, `&'
matches the previous history line. `&' may be escaped using a
backslash; the backslash is removed before attempting a match.
The second and subsequent lines of a multi-line compound command are
not tested, and are added to the history regardless of the value of
HISTIGNORE.
- HISTSIZE
-
The number of commands to remember in the command history (see
HISTORY
below).
If the value is 0, commands are not saved in the history list.
Numeric values less than zero result in every command being saved
on the history list (there is no limit).
The shell sets the default value to 500 after reading any startup files.
- HISTTIMEFORMAT
-
If this variable is set and not null, its value is used as a format string
for strftime(3) to print the time stamp associated with each history
entry displayed by the history builtin.
If this variable is set, time stamps are written to the history file so
they may be preserved across shell sessions.
This uses the history comment character to distinguish timestamps from
other history lines.
- HOME
-
The home directory of the current user; the default argument for the
cd builtin command.
The value of this variable is also used when performing tilde expansion.
- HOSTFILE
-
Contains the name of a file in the same format as
/etc/hosts
that should be read when the shell needs to complete a
hostname.
The list of possible hostname completions may be changed while the
shell is running;
the next time hostname completion is attempted after the
value is changed,
bash
adds the contents of the new file to the existing list.
If
HOSTFILE
is set, but has no value, or does not name a readable file,
bash attempts to read
/etc/hosts
to obtain the list of possible hostname completions.
When
HOSTFILE
is unset, the hostname list is cleared.
- IFS
-
The
Internal Field Separator
that is used
for word splitting after expansion and to
split lines into words with the
read
builtin command. The default value is
``<space><tab><newline>''.
- IGNOREEOF
-
Controls the
action of an interactive shell on receipt of an
EOF
character as the sole input. If set, the value is the number of
consecutive
EOF
characters which must be
typed as the first characters on an input line before
bash
exits. If the variable exists but does not have a numeric value, or
has no value, the default value is 10. If it does not exist,
EOF
signifies the end of input to the shell.
- INPUTRC
-
The filename for the
readline
startup file, overriding the default of
~/.inputrc
(see
READLINE
below).
- LANG
-
Used to determine the locale category for any category not specifically
selected with a variable starting with LC_.
- LC_ALL
-
This variable overrides the value of
LANG
and any other
LC_ variable specifying a locale category.
- LC_COLLATE
-
This variable determines the collation order used when sorting the
results of pathname expansion, and determines the behavior of range
expressions, equivalence classes, and collating sequences within
pathname expansion and pattern matching.
- LC_CTYPE
-
This variable determines the interpretation of characters and the
behavior of character classes within pathname expansion and pattern
matching.
- LC_MESSAGES
-
This variable determines the locale used to translate double-quoted
strings preceded by a $.
- LC_NUMERIC
-
This variable determines the locale category used for number formatting.
- LINES
-
Used by the select compound command to determine the column length
for printing selection lists.
Automatically set if the
checkwinsize
option is enabled or in an interactive shell upon receipt of a
SIGWINCH.
- MAIL
-
If this parameter is set to a file or directory name and the
MAILPATH
variable is not set,
bash
informs the user of the arrival of mail in the specified file or
Maildir-format directory.
- MAILCHECK
-
Specifies how
often (in seconds)
bash
checks for mail. The default is 60 seconds. When it is time to check
for mail, the shell does so before displaying the primary prompt.
If this variable is unset, or set to a value that is not a number
greater than or equal to zero, the shell disables mail checking.
- MAILPATH
-
A colon-separated list of filenames to be checked for mail.
The message to be printed when mail arrives in a particular file
may be specified by separating the filename from the message with a `?'.
When used in the text of the message, $_ expands to the name of
the current mailfile.
Example:
-
MAILPATH=aq/var/mail/bfox?"You have mail":~/shell-mail?"$_ has mail!"aq
Bash
supplies a default value for this variable, but the location of the user
mail files that it uses is system dependent (e.g., /var/mail/$USER).
- OPTERR
-
If set to the value 1,
bash
displays error messages generated by the
getopts
builtin command (see
SHELL BUILTIN COMMANDS
below).
OPTERR
is initialized to 1 each time the shell is invoked or a shell
script is executed.
- PATH
-
The search path for commands. It
is a colon-separated list of directories in which
the shell looks for commands (see
COMMAND EXECUTION
below).
A zero-length (null) directory name in the value of
PATH
indicates the current directory.
A null directory name may appear as two adjacent colons, or as an initial
or trailing colon.
The default path is system-dependent,
and is set by the administrator who installs
bash.
A common value is
/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin.
- POSIXLY_CORRECT
-
If this variable is in the environment when bash starts, the shell
enters posix mode before reading the startup files, as if the
--posix
invocation option had been supplied. If it is set while the shell is
running, bash enables posix mode, as if the command
set -o posix
had been executed.
- PROMPT_COMMAND
-
If set, the value is executed as a command prior to issuing each primary
prompt.
- PROMPT_DIRTRIM
-
If set to a number greater than zero, the value is used as the number of
trailing directory components to retain when expanding the \w and
\W prompt string escapes (see
PROMPTING
below). Characters removed are replaced with an ellipsis.
- PS1
-
The value of this parameter is expanded (see
PROMPTING
below) and used as the primary prompt string. The default value is
``\s-\v\$ ''.
- PS2
-
The value of this parameter is expanded as with
PS1
and used as the secondary prompt string. The default is
``> ''.
- PS3
-
The value of this parameter is used as the prompt for the
select
command (see
SHELL GRAMMAR
above).
- PS4
-
The value of this parameter is expanded as with
PS1
and the value is printed before each command
bash
displays during an execution trace. The first character of
PS4
is replicated multiple times, as necessary, to indicate multiple
levels of indirection. The default is ``+ ''.
- SHELL
-
The full pathname to the shell is kept in this environment variable.
If it is not set when the shell starts,
bash
assigns to it the full pathname of the current user's login shell.
- TIMEFORMAT
-
The value of this parameter is used as a format string specifying
how the timing information for pipelines prefixed with the
time
reserved word should be displayed.
The % character introduces an escape sequence that is
expanded to a time value or other information.
The escape sequences and their meanings are as follows; the
braces denote optional portions.
-
- %%
-
A literal %.
- %[p][l]R
-
The elapsed time in seconds.
- %[p][l]U
-
The number of CPU seconds spent in user mode.
- %[p][l]S
-
The number of CPU seconds spent in system mode.
- %P
-
The CPU percentage, computed as (%U + %S) / %R.
-
The optional p is a digit specifying the precision,
the number of fractional digits after a decimal point.
A value of 0 causes no decimal point or fraction to be output.
At most three places after the decimal point may be specified;
values of p greater than 3 are changed to 3.
If p is not specified, the value 3 is used.
-
The optional l specifies a longer format, including
minutes, of the form MMmSS.FFs.
The value of p determines whether or not the fraction is
included.
-
If this variable is not set, bash acts as if it had the
value $aq\nreal\t%3lR\nuser\t%3lU\nsys\t%3lSaq.
If the value is null, no timing information is displayed.
A trailing newline is added when the format string is displayed.
- TMOUT
-
If set to a value greater than zero,
TMOUT
is treated as the
default timeout for the read builtin.
The select command terminates if input does not arrive
after
TMOUT
seconds when input is coming from a terminal.
In an interactive shell, the value is interpreted as the
number of seconds to wait for a line of input after issuing the
primary prompt.
Bash
terminates after waiting for that number of seconds if a complete
line of input does not arrive.
- TMPDIR
-
If set, bash uses its value as the name of a directory in which
bash creates temporary files for the shell's use.
- auto_resume
-
This variable controls how the shell interacts with the user and
job control. If this variable is set, single word simple
commands without redirections are treated as candidates for resumption
of an existing stopped job. There is no ambiguity allowed; if there is
more than one job beginning with the string typed, the job most recently
accessed is selected. The
name
of a stopped job, in this context, is the command line used to
start it.
If set to the value
exact,
the string supplied must match the name of a stopped job exactly;
if set to
substring,
the string supplied needs to match a substring of the name of a
stopped job. The
substring
value provides functionality analogous to the
%?
job identifier (see
JOB CONTROL
below). If set to any other value, the supplied string must
be a prefix of a stopped job's name; this provides functionality
analogous to the %string job identifier.
- histchars
-
The two or three characters which control history expansion
and tokenization (see
HISTORY EXPANSION
below). The first character is the history expansion character,
the character which signals the start of a history
expansion, normally `!'.
The second character is the quick substitution
character, which is used as shorthand for re-running the previous
command entered, substituting one string for another in the command.
The default is `^'.
The optional third character is the character
which indicates that the remainder of the line is a comment when found
as the first character of a word, normally `#'. The history
comment character causes history substitution to be skipped for the
remaining words on the line. It does not necessarily cause the shell
parser to treat the rest of the line as a comment.
Arrays
Bash
provides one-dimensional indexed and associative array variables.
Any variable may be used as an indexed array; the
declare
builtin will explicitly declare an array.
There is no maximum
limit on the size of an array, nor any requirement that members
be indexed or assigned contiguously.
Indexed arrays are referenced using integers (including arithmetic
expressions) and are zero-based; associative arrays are referenced
using arbitrary strings.
Unless otherwise noted, indexed array indices must be non-negative integers.
An indexed array is created automatically if any variable is assigned to
using the syntax name[subscript]=value. The
subscript
is treated as an arithmetic expression that must evaluate to a number.
To explicitly declare an indexed array, use
declare -a name
(see
SHELL BUILTIN COMMANDS
below).
declare -a name[subscript]
is also accepted; the subscript is ignored.
Associative arrays are created using
declare -A name.
Attributes may be
specified for an array variable using the
declare
and
readonly
builtins. Each attribute applies to all members of an array.
Arrays are assigned to using compound assignments of the form
name=(value1 ... valuen), where each
value is of the form [subscript]=string.
Indexed array assignments do not require anything but string.
When assigning to indexed arrays, if the optional brackets and subscript
are supplied, that index is assigned to;
otherwise the index of the element assigned is the last index assigned
to by the statement plus one. Indexing starts at zero.
When assigning to an associative array, the subscript is required.
This syntax is also accepted by the
declare
builtin. Individual array elements may be assigned to using the
name[subscript]=value syntax introduced above.
When assigning to an indexed array, if
name
is subscripted by a negative number, that number is
interpreted as relative to one greater than the maximum index of
name, so negative indices count back from the end of the
array, and an index of -1 references the last element.
Any element of an array may be referenced using
${name[subscript]}. The braces are required to avoid
conflicts with pathname expansion. If
subscript is @ or *, the word expands to
all members of name. These subscripts differ only when the
word appears within double quotes. If the word is double-quoted,
${name[*]} expands to a single
word with the value of each array member separated by the first
character of the
IFS
special variable, and ${name[@]} expands each element of
name to a separate word. When there are no array members,
${name[@]} expands to nothing.
If the double-quoted expansion occurs within a word, the expansion of
the first parameter is joined with the beginning part of the original
word, and the expansion of the last parameter is joined with the last
part of the original word.
This is analogous to the expansion
of the special parameters * and @ (see
Special Parameters
above). ${#name[subscript]} expands to the length of
${name[subscript]}. If subscript is * or
@, the expansion is the number of elements in the array.
Referencing an array variable without a subscript is equivalent to
referencing the array with a subscript of 0.
If the
subscript
used to reference an element of an indexed array
evaluates to a number less than zero, it is
interpreted as relative to one greater than the maximum index of the array,
so negative indices count back from the end of the
array, and an index of -1 references the last element.
An array variable is considered set if a subscript has been assigned a
value. The null string is a valid value.
It is possible to obtain the keys (indices) of an array as well as the values.
${!name[@]} and ${!name[*]}
expand to the indices assigned in array variable name.
The treatment when in double quotes is similar to the expansion of the
special parameters @ and * within double quotes.
The
unset
builtin is used to destroy arrays. unset name[subscript]
destroys the array element at index subscript.
Negative subscripts to indexed arrays are interpreted as described above.
Care must be taken to avoid unwanted side effects caused by pathname
expansion.
unset name, where name is an array, or
unset name[subscript], where
subscript is * or @, removes the entire array.
The
declare,
local,
and
readonly
builtins each accept a
-a
option to specify an indexed array and a
-A
option to specify an associative array.
If both options are supplied,
-A
takes precedence.
The
read
builtin accepts a
-a
option to assign a list of words read from the standard input
to an array. The
set
and
declare
builtins display array values in a way that allows them to be
reused as assignments.
EXPANSION
Expansion is performed on the command line after it has been split into
words. There are seven kinds of expansion performed:
brace expansion,
tilde expansion,
parameter and variable expansion,
command substitution,
arithmetic expansion,
word splitting,
and
pathname expansion.
The order of expansions is:
brace expansion;
tilde expansion, parameter and variable expansion, arithmetic expansion,
and command substitution (done in a left-to-right fashion);
word splitting;
and pathname expansion.
On systems that can support it, there is an additional expansion
available: process substitution.
This is performed at the
same time as tilde, parameter, variable, and arithmetic expansion and
command substitution.
Only brace expansion, word splitting, and pathname expansion
can change the number of words of the expansion; other expansions
expand a single word to a single word.
The only exceptions to this are the expansions of
"$@" and "${name[@]}"
as explained above (see
PARAMETERS).
Brace Expansion
Brace expansion
is a mechanism by which arbitrary strings
may be generated. This mechanism is similar to
pathname expansion, but the filenames generated
need not exist. Patterns to be brace expanded take
the form of an optional
preamble,
followed by either a series of comma-separated strings or
a sequence expression between a pair of braces, followed by
an optional
postscript.
The preamble is prefixed to each string contained
within the braces, and the postscript is then appended
to each resulting string, expanding left to right.
Brace expansions may be nested. The results of each expanded
string are not sorted; left to right order is preserved.
For example, a{d,c,b}e expands into `ade ace abe'.
A sequence expression takes the form
{x..y[..incr]},
where x and y are either integers or single characters,
and incr, an optional increment, is an integer.
When integers are supplied, the expression expands to each number between
x and y, inclusive.
Supplied integers may be prefixed with 0 to force each term to have the
same width.
When either x or y begins with a zero, the shell
attempts to force all generated terms to contain the same number of digits,
zero-padding where necessary.
When characters are supplied, the expression expands to each character
lexicographically between x and y, inclusive,
using the default C locale.
Note that both x and y must be of the same type.
When the increment is supplied, it is used as the difference between
each term. The default increment is 1 or -1 as appropriate.
Brace expansion is performed before any other expansions,
and any characters special to other expansions are preserved
in the result. It is strictly textual.
Bash
does not apply any syntactic interpretation to the context of the
expansion or the text between the braces.
A correctly-formed brace expansion must contain unquoted opening
and closing braces, and at least one unquoted comma or a valid
sequence expression.
Any incorrectly formed brace expansion is left unchanged.
A { or , may be quoted with a backslash to prevent its
being considered part of a brace expression.
To avoid conflicts with parameter expansion, the string ${
is not considered eligible for brace expansion.
This construct is typically used as shorthand when the common
prefix of the strings to be generated is longer than in the
above example:
-
mkdir /usr/local/src/bash/{old,new,dist,bugs}
or
-
chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
Brace expansion introduces a slight incompatibility with
historical versions of
sh.
sh
does not treat opening or closing braces specially when they
appear as part of a word, and preserves them in the output.
Bash
removes braces from words as a consequence of brace
expansion. For example, a word entered to
sh
as file{1,2}
appears identically in the output. The same word is
output as
file1 file2
after expansion by
bash.
If strict compatibility with
sh
is desired, start
bash
with the
+B
option or disable brace expansion with the
+B
option to the
set
command (see
SHELL BUILTIN COMMANDS
below).
Tilde Expansion
If a word begins with an unquoted tilde character (`~'), all of
the characters preceding the first unquoted slash (or all characters,
if there is no unquoted slash) are considered a tilde-prefix.
If none of the characters in the tilde-prefix are quoted, the
characters in the tilde-prefix following the tilde are treated as a
possible login name.
If this login name is the null string, the tilde is replaced with the
value of the shell parameter
HOME.
If
HOME
is unset, the home directory of the user executing the shell is
substituted instead.
Otherwise, the tilde-prefix is replaced with the home directory
associated with the specified login name.
If the tilde-prefix is a `~+', the value of the shell variable
PWD
replaces the tilde-prefix.
If the tilde-prefix is a `~-', the value of the shell variable
OLDPWD,
if it is set, is substituted.
If the characters following the tilde in the tilde-prefix consist
of a number N, optionally prefixed
by a `+' or a `-', the tilde-prefix is replaced with the corresponding
element from the directory stack, as it would be displayed by the
dirs
builtin invoked with the tilde-prefix as an argument.
If the characters following the tilde in the tilde-prefix consist of a
number without a leading `+' or `-', `+' is assumed.
If the login name is invalid, or the tilde expansion fails, the word
is unchanged.
Each variable assignment is checked for unquoted tilde-prefixes immediately
following a
:
or the first
=.
In these cases, tilde expansion is also performed.
Consequently, one may use filenames with tildes in assignments to
PATH,
MAILPATH,
and
CDPATH,
and the shell assigns the expanded value.
Parameter Expansion
The `$' character introduces parameter expansion,
command substitution, or arithmetic expansion. The parameter name
or symbol to be expanded may be enclosed in braces, which
are optional but serve to protect the variable to be expanded from
characters immediately following it which could be
interpreted as part of the name.
When braces are used, the matching ending brace is the first `}'
not escaped by a backslash or within a quoted string, and not within an
embedded arithmetic expansion, command substitution, or parameter
expansion.
- ${parameter}
-
The value of parameter is substituted. The braces are required
when
parameter
is a positional parameter with more than one digit,
or when
parameter
is followed by a character which is not to be
interpreted as part of its name.
The parameter is a shell parameter as described above
PARAMETERS) or an array reference (Arrays).
If the first character of parameter is an exclamation point (!),
it introduces a level of variable indirection.
Bash uses the value of the variable formed from the rest of
parameter as the name of the variable; this variable is then
expanded and that value is used in the rest of the substitution, rather
than the value of parameter itself.
This is known as indirect expansion.
The exceptions to this are the expansions of ${!prefix*} and
${!name[@]} described below.
The exclamation point must immediately follow the left brace in order to
introduce indirection.
In each of the cases below, word is subject to tilde expansion,
parameter expansion, command substitution, and arithmetic expansion.
When not performing substring expansion, using the forms documented below
(e.g., :-),
bash tests for a parameter that is unset or null. Omitting the colon
results in a test only for a parameter that is unset.
- ${parameter:-word}
-
Use Default Values. If
parameter
is unset or null, the expansion of
word
is substituted. Otherwise, the value of
parameter
is substituted.
- ${parameter:=word}
-
Assign Default Values.
If
parameter
is unset or null, the expansion of
word
is assigned to
parameter.
The value of
parameter
is then substituted. Positional parameters and special parameters may
not be assigned to in this way.
- ${parameter:?word}
-
Display Error if Null or Unset.
If
parameter
is null or unset, the expansion of word (or a message to that effect
if
word
is not present) is written to the standard error and the shell, if it
is not interactive, exits. Otherwise, the value of parameter is
substituted.
- ${parameter:+word}
-
Use Alternate Value.
If
parameter
is null or unset, nothing is substituted, otherwise the expansion of
word
is substituted.
- ${parameter:offset}
-
- ${parameter:offset:length}
-
Substring Expansion.
Expands to up to length characters of the value of parameter
starting at the character specified by offset.
If parameter is @, an indexed array subscripted by
@ or *, or an associative array name, the results differ as
described below.
If length is omitted, expands to the substring of the value of
parameter starting at the character specified by offset
and extending to the end of the value.
length and offset are arithmetic expressions (see
ARITHMETIC EVALUATION
below).
If offset evaluates to a number less than zero, the value
is used as an offset in characters
from the end of the value of parameter.
If length evaluates to a number less than zero,
it is interpreted as an offset in characters
from the end of the value of parameter rather than
a number of characters, and the expansion is the characters between
offset and that result.
Note that a negative offset must be separated from the colon by at least
one space to avoid being confused with the :- expansion.
If parameter is @, the result is length positional
parameters beginning at offset.
A negative offset is taken relative to one greater than the greatest
positional parameter, so an offset of -1 evaluates to the last positional
parameter.
It is an expansion error if length evaluates to a number less than
zero.
If parameter is an indexed array name subscripted by @ or *,
the result is the length
members of the array beginning with ${parameter[offset]}.
A negative offset is taken relative to one greater than the maximum
index of the specified array.
It is an expansion error if length evaluates to a number less than
zero.
Substring expansion applied to an associative array produces undefined
results.
Substring indexing is zero-based unless the positional parameters
are used, in which case the indexing starts at 1 by default.
If offset is 0, and the positional parameters are used, $0 is
prefixed to the list.
- ${!prefix*}
-
- ${!prefix@}
-
Names matching prefix.
Expands to the names of variables whose names begin with prefix,
separated by the first character of the
IFS
special variable.
When @ is used and the expansion appears within double quotes, each
variable name expands to a separate word.
- ${!name[@]}
-
- ${!name[*]}
-
List of array keys.
If name is an array variable, expands to the list of array indices
(keys) assigned in name.
If name is not an array, expands to 0 if name is set and null
otherwise.
When @ is used and the expansion appears within double quotes, each
key expands to a separate word.
- ${#parameter}
-
Parameter length.
The length in characters of the value of parameter is substituted.
If
parameter
is
*
or
@,
the value substituted is the number of positional parameters.
If
parameter
is an array name subscripted by
*
or
@,
the value substituted is the number of elements in the array.
If
parameter
is an indexed array name subscripted by a negative number, that number is
interpreted as relative to one greater than the maximum index of
parameter, so negative indices count back from the end of the
array, and an index of -1 references the last element.
- ${parameter#word}
-
- ${parameter##word}
-
Remove matching prefix pattern.
The
word
is expanded to produce a pattern just as in pathname
expansion. If the pattern matches the beginning of
the value of
parameter,
then the result of the expansion is the expanded value of
parameter
with the shortest matching pattern (the ``#'' case) or the
longest matching pattern (the ``##'' case) deleted.
If
parameter
is
@
or
*,
the pattern removal operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If
parameter
is an array variable subscripted with
@
or
*,
the pattern removal operation is applied to each member of the
array in turn, and the expansion is the resultant list.
- ${parameter%word}
-
- ${parameter%%word}
-
Remove matching suffix pattern.
The word is expanded to produce a pattern just as in
pathname expansion.
If the pattern matches a trailing portion of the expanded value of
parameter,
then the result of the expansion is the expanded value of
parameter
with the shortest matching pattern (the ``%'' case) or the
longest matching pattern (the ``%%'' case) deleted.
If
parameter
is
@
or
*,
the pattern removal operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If
parameter
is an array variable subscripted with
@
or
*,
the pattern removal operation is applied to each member of the
array in turn, and the expansion is the resultant list.
- ${parameter/pattern/string}
-
Pattern substitution.
The pattern is expanded to produce a pattern just as in
pathname expansion.
Parameter is expanded and the longest match of pattern
against its value is replaced with string.
If pattern begins with /, all matches of pattern are
replaced with string. Normally only the first match is replaced.
If pattern begins with #, it must match at the beginning
of the expanded value of parameter.
If pattern begins with %, it must match at the end
of the expanded value of parameter.
If string is null, matches of pattern are deleted
and the / following pattern may be omitted.
If
parameter
is
@
or
*,
the substitution operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If
parameter
is an array variable subscripted with
@
or
*,
the substitution operation is applied to each member of the
array in turn, and the expansion is the resultant list.
- ${parameter^pattern}
-
- ${parameter^^pattern}
-
- ${parameter,pattern}
-
- ${parameter,,pattern}
-
Case modification.
This expansion modifies the case of alphabetic characters in parameter.
The pattern is expanded to produce a pattern just as in
pathname expansion.
Each character in the expanded value of parameter is tested against
pattern, and, if it matches the pattern, its case is converted.
The pattern should not attempt to match more than one character.
The ^ operator converts lowercase letters matching pattern
to uppercase; the , operator converts matching uppercase letters
to lowercase.
The ^^ and ,, expansions convert each matched character in the
expanded value; the ^ and , expansions match and convert only
the first character in the expanded value.
If pattern is omitted, it is treated like a ?, which matches
every character.
If
parameter
is
@
or
*,
the case modification operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If
parameter
is an array variable subscripted with
@
or
*,
the case modification operation is applied to each member of the
array in turn, and the expansion is the resultant list.
Command Substitution
Command substitution allows the output of a command to replace
the command name. There are two forms:
-
$(command)
or
-
`command`
Bash
performs the expansion by executing command and
replacing the command substitution with the standard output of the
command, with any trailing newlines deleted.
Embedded newlines are not deleted, but they may be removed during
word splitting.
The command substitution $(cat file) can be replaced by
the equivalent but faster $(< file).
When the old-style backquote form of substitution is used,
backslash retains its literal meaning except when followed by
$,
`,
or
\.
The first backquote not preceded by a backslash terminates the
command substitution.
When using the $(command) form, all characters between the
parentheses make up the command; none are treated specially.
Command substitutions may be nested. To nest when using the backquoted form,
escape the inner backquotes with backslashes.
If the substitution appears within double quotes, word splitting and
pathname expansion are not performed on the results.
Arithmetic Expansion
Arithmetic expansion allows the evaluation of an arithmetic expression
and the substitution of the result. The format for arithmetic expansion is:
-
$((expression))
The
expression
is treated as if it were within double quotes, but a double quote
inside the parentheses is not treated specially.
All tokens in the expression undergo parameter and variable expansion,
command substitution, and quote removal.
The result is treated as the arithmetic expression to be evaluated.
Arithmetic expansions may be nested.
The evaluation is performed according to the rules listed below under
ARITHMETIC EVALUATION.
If
expression
is invalid,
bash
prints a message indicating failure and no substitution occurs.
Process Substitution
Process substitution is supported on systems that support named
pipes (FIFOs) or the /dev/fd method of naming open files.
It takes the form of
<(list)
or
>(list).
The process list is run with its input or output connected to a
FIFO or some file in /dev/fd. The name of this file is
passed as an argument to the current command as the result of the
expansion. If the >(list) form is used, writing to
the file will provide input for list. If the
<(list) form is used, the file passed as an
argument should be read to obtain the output of list.
When available, process substitution is performed
simultaneously with parameter and variable expansion,
command substitution,
and arithmetic expansion.
Word Splitting
The shell scans the results of
parameter expansion,
command substitution,
and
arithmetic expansion
that did not occur within double quotes for
word splitting.
The shell treats each character of
IFS
as a delimiter, and splits the results of the other
expansions into words using these characters as field terminators.
If
IFS
is unset, or its
value is exactly
<space><tab><newline>,
the default, then
sequences of
<space>,
<tab>,
and
<newline>
at the beginning and end of the results of the previous
expansions are ignored, and
any sequence of
IFS
characters not at the beginning or end serves to delimit words.
If
IFS
has a value other than the default, then sequences of
the whitespace characters
space
and
tab
are ignored at the beginning and end of the
word, as long as the whitespace character is in the
value of
IFS
(an
IFS
whitespace character).
Any character in
IFS
that is not
IFS
whitespace, along with any adjacent
IFS
whitespace characters, delimits a field.
A sequence of
IFS
whitespace characters is also treated as a delimiter.
If the value of
IFS
is null, no word splitting occurs.
Explicit null arguments ("" or aqaq) are retained.
Unquoted implicit null arguments, resulting from the expansion of
parameters that have no values, are removed.
If a parameter with no value is expanded within double quotes, a
null argument results and is retained.
Note that if no expansion occurs, no splitting
is performed.
Pathname Expansion
After word splitting,
unless the
-f
option has been set,
bash
scans each word for the characters
*,
?,
and
[.
If one of these characters appears, then the word is
regarded as a
pattern,
and replaced with an alphabetically sorted list of
filenames matching the pattern
(see
Pattern Matching
below).
If no matching filenames are found,
and the shell option
nullglob
is not enabled, the word is left unchanged.
If the
nullglob
option is set, and no matches are found,
the word is removed.
If the
failglob
shell option is set, and no matches are found, an error message
is printed and the command is not executed.
If the shell option
nocaseglob
is enabled, the match is performed without regard to the case
of alphabetic characters.
When a pattern is used for pathname expansion,
the character
``.''
at the start of a name or immediately following a slash
must be matched explicitly, unless the shell option
dotglob
is set.
When matching a pathname, the slash character must always be
matched explicitly.
In other cases, the
``.''
character is not treated specially.
See the description of
shopt
below under
SHELL BUILTIN COMMANDS
for a description of the
nocaseglob,
nullglob,
failglob,
and
dotglob
shell options.
The
GLOBIGNORE
shell variable may be used to restrict the set of filenames matching a
pattern.
If
GLOBIGNORE
is set, each matching filename that also matches one of the patterns in
GLOBIGNORE
is removed from the list of matches.
The filenames
``.''
and
``..''
are always ignored when
GLOBIGNORE
is set and not null. However, setting
GLOBIGNORE
to a non-null value has the effect of enabling the
dotglob
shell option, so all other filenames beginning with a
``.''
will match.
To get the old behavior of ignoring filenames beginning with a
``.'',
make
``.*''
one of the patterns in
GLOBIGNORE.
The
dotglob
option is disabled when
GLOBIGNORE
is unset.
Pattern Matching
Any character that appears in a pattern, other than the special pattern
characters described below, matches itself. The NUL character may not
occur in a pattern. A backslash escapes the following character; the
escaping backslash is discarded when matching.
The special pattern characters must be quoted if
they are to be matched literally.
The special pattern characters have the following meanings:
-
- *
-
Matches any string, including the null string.
When the globstar shell option is enabled, and * is used in
a pathname expansion context, two adjacent *s used as a single
pattern will match all files and zero or more directories and
subdirectories.
If followed by a /, two adjacent *s will match only directories
and subdirectories.
- ?
-
Matches any single character.
- [...]
-
Matches any one of the enclosed characters. A pair of characters
separated by a hyphen denotes a
range expression;
any character that falls between those two characters, inclusive,
using the current locale's collating sequence and character set,
is matched. If the first character following the
[
is a
!
or a
^
then any character not enclosed is matched.
The sorting order of characters in range expressions is determined by
the current locale and the values of the
LC_COLLATE
or
LC_ALL
shell variables, if set.
To obtain the traditional interpretation of range expressions, where
[a-d]
is equivalent to
[abcd],
set value of the
LC_ALL
shell variable to
C,
or enable the
globasciiranges
shell option.
A
-
may be matched by including it as the first or last character
in the set.
A
]
may be matched by including it as the first character
in the set.
Within
[
and
],
character classes can be specified using the syntax
[:class:], where class is one of the
following classes defined in the POSIX standard:
-
alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
A character class matches any character belonging to that class.
The word character class matches letters, digits, and the character _.
Within
[
and
],
an equivalence class can be specified using the syntax
[=c=], which matches all characters with the
same collation weight (as defined by the current locale) as
the character c.
Within
[
and
],
the syntax [.symbol.] matches the collating symbol
symbol.
If the extglob shell option is enabled using the shopt
builtin, several extended pattern matching operators are recognized.
In the following description, a pattern-list is a list of one
or more patterns separated by a |.
Composite patterns may be formed using one or more of the following
sub-patterns:
-
- ?(pattern-list)
-
Matches zero or one occurrence of the given patterns
- *(pattern-list)
-
Matches zero or more occurrences of the given patterns
- +(pattern-list)
-
Matches one or more occurrences of the given patterns
- @(pattern-list)
-
Matches one of the given patterns
- !(pattern-list)
-
Matches anything except one of the given patterns
Quote Removal
After the preceding expansions, all unquoted occurrences of the
characters
\,
aq,
and " that did not result from one of the above
expansions are removed.
REDIRECTION
Before a command is executed, its input and output
may be
redirected
using a special notation interpreted by the shell.
Redirection allows commands' file handles to be
duplicated, opened, closed,
made to refer to different files,
and can change the files the command reads from and writes to.
Redirection may also be used to modify file handles in the
current shell execution environment.
The following redirection
operators may precede or appear anywhere within a
simple command
or may follow a
command.
Redirections are processed in the order they appear, from
left to right.
Each redirection that may be preceded by a file descriptor number
may instead be preceded by a word of the form {varname}.
In this case, for each redirection operator except
>&- and <&-, the shell will allocate a file descriptor greater
than or equal to 10 and assign it to varname.
If >&- or <&- is preceded
by {varname}, the value of varname defines the file
descriptor to close.
In the following descriptions, if the file descriptor number is
omitted, and the first character of the redirection operator is
<,
the redirection refers to the standard input (file descriptor
0). If the first character of the redirection operator is
>,
the redirection refers to the standard output (file descriptor
1).
The word following the redirection operator in the following
descriptions, unless otherwise noted, is subjected to
brace expansion, tilde expansion, parameter and variable expansion,
command substitution, arithmetic expansion, quote removal,
pathname expansion, and word splitting.
If it expands to more than one word,
bash
reports an error.
Note that the order of redirections is significant. For example,
the command
-
ls > dirlist 2>&1
directs both standard output and standard error to the file
dirlist,
while the command
-
ls 2>&1 > dirlist
directs only the standard output to file
dirlist,
because the standard error was duplicated from the standard output
before the standard output was redirected to
dirlist.
Bash handles several filenames specially when they are used in
redirections, as described in the following table:
-
- /dev/fd/fd
-
If fd is a valid integer, file descriptor fd is duplicated.
- /dev/stdin
-
File descriptor 0 is duplicated.
- /dev/stdout
-
File descriptor 1 is duplicated.
- /dev/stderr
-
File descriptor 2 is duplicated.
- /dev/tcp/host/port
-
If host is a valid hostname or Internet address, and port
is an integer port number or service name, bash attempts to open
the corresponding TCP socket.
- /dev/udp/host/port
-
If host is a valid hostname or Internet address, and port
is an integer port number or service name, bash attempts to open
the corresponding UDP socket.
A failure to open or create a file causes the redirection to fail.
Redirections using file descriptors greater than 9 should be used with
care, as they may conflict with file descriptors the shell uses
internally.
Redirecting Input
Redirection of input causes the file whose name results from
the expansion of
word
to be opened for reading on file descriptor
n,
or the standard input (file descriptor 0) if
n
is not specified.
The general format for redirecting input is:
-
[n]<word
Redirecting Output
Redirection of output causes the file whose name results from
the expansion of
word
to be opened for writing on file descriptor
n,
or the standard output (file descriptor 1) if
n
is not specified. If the file does not exist it is created;
if it does exist it is truncated to zero size.
The general format for redirecting output is:
-
[n]>word
If the redirection operator is
>,
and the
noclobber
option to the
set
builtin has been enabled, the redirection will fail if the file
whose name results from the expansion of word exists and is
a regular file.
If the redirection operator is
>|,
or the redirection operator is
>
and the
noclobber
option to the
set
builtin command is not enabled, the redirection is attempted even
if the file named by word exists.
Appending Redirected Output
Redirection of output in this fashion
causes the file whose name results from
the expansion of
word
to be opened for appending on file descriptor
n,
or the standard output (file descriptor 1) if
n
is not specified. If the file does not exist it is created.
The general format for appending output is:
-
[n]>>word
Redirecting Standard Output and Standard Error
This construct allows both the
standard output (file descriptor 1) and
the standard error output (file descriptor 2)
to be redirected to the file whose name is the
expansion of
word.
There are two formats for redirecting standard output and
standard error:
-
&>word
and
-
>&word
Of the two forms, the first is preferred.
This is semantically equivalent to
-
>word 2>&1
When using the second form, word may not expand to a number or
-. If it does, other redirection operators apply
(see Duplicating File Descriptors below) for compatibility
reasons.
Appending Standard Output and Standard Error
This construct allows both the
standard output (file descriptor 1) and
the standard error output (file descriptor 2)
to be appended to the file whose name is the
expansion of
word.
The format for appending standard output and standard error is:
-
&>>word
This is semantically equivalent to
-
>>word 2>&1
(see Duplicating File Descriptors below).
Here Documents
This type of redirection instructs the shell to read input from the
current source until a line containing only
delimiter
(with no trailing blanks)
is seen. All of
the lines read up to that point are then used as the standard
input for a command.
The format of here-documents is:
-
<<[-]word
here-document
delimiter
No parameter and variable expansion, command substitution,
arithmetic expansion, or pathname expansion is performed on
word.
If any characters in
word
are quoted, the
delimiter
is the result of quote removal on
word,
and the lines in the here-document are not expanded.
If word is unquoted,
all lines of the here-document are subjected to
parameter expansion, command substitution, and arithmetic expansion,
the character sequence
\<newline>
is ignored, and
\
must be used to quote the characters
\,
$,
and
`.
If the redirection operator is
<<-,
then all leading tab characters are stripped from input lines and the
line containing
delimiter.
This allows
here-documents within shell scripts to be indented in a
natural fashion.
Here Strings
A variant of here documents, the format is:
-
<<<word
The word undergoes
brace expansion, tilde expansion, parameter and variable expansion,
command substitution, arithmetic expansion, and quote removal.
Pathname expansion and word splitting are not performed.
The result is supplied as a single string to the command on its
standard input.
Duplicating File Descriptors
The redirection operator
-
[n]<&word
is used to duplicate input file descriptors.
If
word
expands to one or more digits, the file descriptor denoted by
n
is made to be a copy of that file descriptor.
If the digits in
word
do not specify a file descriptor open for input, a redirection error occurs.
If
word
evaluates to
-,
file descriptor
n
is closed. If
n
is not specified, the standard input (file descriptor 0) is used.
The operator
-
[n]>&word
is used similarly to duplicate output file descriptors. If
n
is not specified, the standard output (file descriptor 1) is used.
If the digits in
word
do not specify a file descriptor open for output, a redirection error occurs.
If
word
evaluates to
-,
file descriptor
n
is closed.
As a special case, if n is omitted, and word does not
expand to one or more digits or -, the standard output and standard
error are redirected as described previously.
Moving File Descriptors
The redirection operator
-
[n]<&digit-
moves the file descriptor digit to file descriptor
n,
or the standard input (file descriptor 0) if n is not specified.
digit is closed after being duplicated to n.
Similarly, the redirection operator
-
[n]>&digit-
moves the file descriptor digit to file descriptor
n,
or the standard output (file descriptor 1) if n is not specified.
Opening File Descriptors for Reading and Writing
The redirection operator
-
[n]<>word
causes the file whose name is the expansion of
word
to be opened for both reading and writing on file descriptor
n,
or on file descriptor 0 if
n
is not specified. If the file does not exist, it is created.
ALIASES
Aliases allow a string to be substituted for a word when it is used
as the first word of a simple command.
The shell maintains a list of aliases that may be set and unset with the
alias
and
unalias
builtin commands (see
SHELL BUILTIN COMMANDS
below).
The first word of each simple command, if unquoted,
is checked to see if it has an
alias. If so, that word is replaced by the text of the alias.
The characters /, $, `, and = and
any of the shell metacharacters or quoting characters
listed above may not appear in an alias name.
The replacement text may contain any valid shell input,
including shell metacharacters.
The first word of the replacement text is tested
for aliases, but a word that is identical to an alias being expanded
is not expanded a second time.
This means that one may alias
ls
to
ls -F,
for instance, and
bash
does not try to recursively expand the replacement text.
If the last character of the alias value is a
blank,
then the next command
word following the alias is also checked for alias expansion.
Aliases are created and listed with the
alias
command, and removed with the
unalias
command.
There is no mechanism for using arguments in the replacement text.
If arguments are needed, a shell function should be used (see
FUNCTIONS
below).
Aliases are not expanded when the shell is not interactive, unless
the
expand_aliases
shell option is set using
shopt
(see the description of
shopt
under
SHELL BUILTIN COMMANDS
below).
The rules concerning the definition and use of aliases are
somewhat confusing.
Bash
always reads at least one complete line
of input before executing any
of the commands on that line. Aliases are expanded when a
command is read, not when it is executed. Therefore, an
alias definition appearing on the same line as another
command does not take effect until the next line of input is read.
The commands following the alias definition
on that line are not affected by the new alias.
This behavior is also an issue when functions are executed.
Aliases are expanded when a function definition is read,
not when the function is executed, because a function definition
is itself a compound command. As a consequence, aliases
defined in a function are not available until after that
function is executed. To be safe, always put
alias definitions on a separate line, and do not use
alias
in compound commands.
For almost every purpose, aliases are superseded by
shell functions.
FUNCTIONS
A shell function, defined as described above under
SHELL GRAMMAR,
stores a series of commands for later execution.
When the name of a shell function is used as a simple command name,
the list of commands associated with that function name is executed.
Functions are executed in the context of the
current shell; no new process is created to interpret
them (contrast this with the execution of a shell script).
When a function is executed, the arguments to the
function become the positional parameters
during its execution.
The special parameter
#
is updated to reflect the change. Special parameter 0
is unchanged.
The first element of the
FUNCNAME
variable is set to the name of the function while the function
is executing.
All other aspects of the shell execution
environment are identical between a function and its caller
with these exceptions: the
DEBUG
and
RETURN
traps (see the description of the
trap
builtin under
SHELL BUILTIN COMMANDS
below) are not inherited unless the function has been given the
trace attribute (see the description of the
declare
builtin below) or the
-o functrace shell option has been enabled with
the set builtin
(in which case all functions inherit the DEBUG and RETURN traps),
and the
ERR
trap is not inherited unless the -o errtrace shell option has
been enabled.
Variables local to the function may be declared with the
local
builtin command. Ordinarily, variables and their values
are shared between the function and its caller.
The FUNCNEST variable, if set to a numeric value greater
than 0, defines a maximum function nesting level. Function
invocations that exceed the limit cause the entire command to
abort.
If the builtin command
return
is executed in a function, the function completes and
execution resumes with the next command after the function
call.
Any command associated with the RETURN trap is executed
before execution resumes.
When a function completes, the values of the
positional parameters and the special parameter
#
are restored to the values they had prior to the function's
execution.
Function names and definitions may be listed with the
-f
option to the
declare
or
typeset
builtin commands. The
-F
option to
declare
or
typeset
will list the function names only
(and optionally the source file and line number, if the extdebug
shell option is enabled).
Functions may be exported so that subshells
automatically have them defined with the
-f
option to the
export
builtin.
A function definition may be deleted using the -f option to
the
unset
builtin.
Note that shell functions and variables with the same name may result
in multiple identically-named entries in the environment passed to the
shell's children.
Care should be taken in cases where this may cause a problem.
Functions may be recursive.
The FUNCNEST variable may be used to limit the depth of the
function call stack and restrict the number of function invocations.
By default, no limit is imposed on the number of recursive calls.
ARITHMETIC EVALUATION
The shell allows arithmetic expressions to be evaluated, under
certain circumstances (see the let and declare builtin
commands and Arithmetic Expansion).
Evaluation is done in fixed-width integers with no check for overflow,
though division by 0 is trapped and flagged as an error.
The operators and their precedence, associativity, and values
are the same as in the C language.
The following list of operators is grouped into levels of
equal-precedence operators.
The levels are listed in order of decreasing precedence.
- id++ id--
-
variable post-increment and post-decrement
- ++id --id
-
variable pre-increment and pre-decrement
- - +
-
unary minus and plus
- ! ~
-
logical and bitwise negation
- **
-
exponentiation
- * / %
-
multiplication, division, remainder
- + -
-
addition, subtraction
- << >>
-
left and right bitwise shifts
- <= >= < >
-
comparison
- == !=
-
equality and inequality
- &
-
bitwise AND
- ^
-
bitwise exclusive OR
- |
-
bitwise OR
- &&
-
logical AND
- ||
-
logical OR
- expr?expr:expr
-
conditional operator
- = *= /= %= += -= <<= >>= &= ^= |=
-
assignment
- expr1 , expr2
-
comma
Shell variables are allowed as operands; parameter expansion is
performed before the expression is evaluated.
Within an expression, shell variables may also be referenced by name
without using the parameter expansion syntax.
A shell variable that is null or unset evaluates to 0 when referenced
by name without using the parameter expansion syntax.
The value of a variable is evaluated as an arithmetic expression
when it is referenced, or when a variable which has been given the
integer attribute using declare -i is assigned a value.
A null value evaluates to 0.
A shell variable need not have its integer attribute
turned on to be used in an expression.
Constants with a leading 0 are interpreted as octal numbers.
A leading 0x or 0X denotes hexadecimal.
Otherwise, numbers take the form [base#]n, where the optional base
is a decimal number between 2 and 64 representing the arithmetic
base, and n is a number in that base.
If base# is omitted, then base 10 is used.
When specifying n,
the digits greater< than 9 are represented by the lowercase letters,
the uppercase letters, @, and _, in that order.
If base is less than or equal to 36, lowercase and uppercase
letters may be used interchangeably to represent numbers between 10
and 35.
Operators are evaluated in order of precedence. Sub-expressions in
parentheses are evaluated first and may override the precedence
rules above.
CONDITIONAL EXPRESSIONS
Conditional expressions are used by the [[ compound command and
the test and [ builtin commands to test file attributes
and perform string and arithmetic comparisons.
Expressions are formed from the following unary or binary primaries.
If any file argument to one of the primaries is of the form
/dev/fd/n, then file descriptor n is checked.
If the file argument to one of the primaries is one of
/dev/stdin, /dev/stdout, or /dev/stderr, file
descriptor 0, 1, or 2, respectively, is checked.
Unless otherwise specified, primaries that operate on files follow symbolic
links and operate on the target of the link, rather than the link itself.
When used with [[, the < and > operators sort
lexicographically using the current locale.
The test command sorts using ASCII ordering.
- -a file
-
True if file exists.
- -b file
-
True if file exists and is a block special file.
- -c file
-
True if file exists and is a character special file.
- -d file
-
True if file exists and is a directory.
- -e file
-
True if file exists.
- -f file
-
True if file exists and is a regular file.
- -g file
-
True if file exists and is set-group-id.
- -h file
-
True if file exists and is a symbolic link.
- -k file
-
True if file exists and its ``sticky'' bit is set.
- -p file
-
True if file exists and is a named pipe (FIFO).
- -r file
-
True if file exists and is readable.
- -s file
-
True if file exists and has a size greater than zero.
- -t fd
-
True if file descriptor
fd
is open and refers to a terminal.
- -u file
-
True if file exists and its set-user-id bit is set.
- -w file
-
True if file exists and is writable.
- -x file
-
True if file exists and is executable.
- -G file
-
True if file exists and is owned by the effective group id.
- -L file
-
True if file exists and is a symbolic link.
- -N file
-
True if file exists and has been modified since it was last read.
- -O file
-
True if file exists and is owned by the effective user id.
- -S file
-
True if file exists and is a socket.
- file1 -ef file2
-
True if file1 and file2 refer to the same device and
inode numbers.
- file1 -nt file2
-
True if file1 is newer (according to modification date) than file2,
or if file1 exists and file2 does not.
- file1 -ot file2
-
True if file1 is older than file2, or if file2 exists
and file1 does not.
- -o optname
-
True if the shell option
optname
is enabled.
See the list of options under the description of the
-o
option to the
set
builtin below.
- -v varname
-
True if the shell variable
varname
is set (has been assigned a value).
- -R varname
-
True if the shell variable
varname
is set and is a name reference.
- -z string
-
True if the length of string is zero.
- string
-
- -n string
-
True if the length of
string
is non-zero.
- string1 == string2
-
- string1 = string2
-
True if the strings are equal. = should be used
with the test command for POSIX conformance.
When used with the [[ command, this performs pattern matching as
described above (Compound Commands).
- string1 != string2
-
True if the strings are not equal.
- string1 < string2
-
True if string1 sorts before string2 lexicographically.
- string1 > string2
-
True if string1 sorts after string2 lexicographically.
- arg1 OP arg2
-
OP
is one of
-eq,
-ne,
-lt,
-le,
-gt,
or
-ge.
These arithmetic binary operators return true if arg1
is equal to, not equal to, less than, less than or equal to,
greater than, or greater than or equal to arg2, respectively.
Arg1
and
arg2
may be positive or negative integers.
SIMPLE COMMAND EXPANSION
When a simple command is executed, the shell performs the following
expansions, assignments, and redirections, from left to right.
- 1.
-
The words that the parser has marked as variable assignments (those
preceding the command name) and redirections are saved for later
processing.
- 2.
-
The words that are not variable assignments or redirections are
expanded. If any words remain after expansion, the first word
is taken to be the name of the command and the remaining words are
the arguments.
- 3.
-
Redirections are performed as described above under
REDIRECTION.
- 4.
-
The text after the = in each variable assignment undergoes tilde
expansion, parameter expansion, command substitution, arithmetic expansion,
and quote removal before being assigned to the variable.
If no command name results, the variable assignments affect the current
shell environment. Otherwise, the variables are added to the environment
of the executed command and do not affect the current shell environment.
If any of the assignments attempts to assign a value to a readonly variable,
an error occurs, and the command exits with a non-zero status.
If no command name results, redirections are performed, but do not
affect the current shell environment. A redirection error causes the
command to exit with a non-zero status.
If there is a command name left after expansion, execution proceeds as
described below. Otherwise, the command exits. If one of the expansions
contained a command substitution, the exit status of the command is
the exit status of the last command substitution performed. If there
were no command substitutions, the command exits with a status of zero.
COMMAND EXECUTION
After a command has been split into words, if it results in a
simple command and an optional list of arguments, the following
actions are taken.
If the command name contains no slashes, the shell attempts to
locate it. If there exists a shell function by that name, that
function is invoked as described above in
FUNCTIONS.
If the name does not match a function, the shell searches for
it in the list of shell builtins. If a match is found, that
builtin is invoked.
If the name is neither a shell function nor a builtin,
and contains no slashes,
bash
searches each element of the
PATH
for a directory containing an executable file by that name.
Bash
uses a hash table to remember the full pathnames of executable
files (see
hash
under
SHELL BUILTIN COMMANDS
below).
A full search of the directories in
PATH
is performed only if the command is not found in the hash table.
If the search is unsuccessful, the shell searches for a defined shell
function named command_not_found_handle.
If that function exists, it is invoked with the original command and
the original command's arguments as its arguments, and the function's
exit status becomes the exit status of the shell.
If that function is not defined, the shell prints an error
message and returns an exit status of 127.
If the search is successful, or if the command name contains
one or more slashes, the shell executes the named program in a
separate execution environment.
Argument 0 is set to the name given, and the remaining arguments
to the command are set to the arguments given, if any.
If this execution fails because the file is not in executable
format, and the file is not a directory, it is assumed to be
a shell script, a file
containing shell commands. A subshell is spawned to execute
it. This subshell reinitializes itself, so
that the effect is as if a new shell had been invoked
to handle the script, with the exception that the locations of
commands remembered by the parent (see
hash
below under
SHELL BUILTIN COMMANDS)
are retained by the child.
If the program is a file beginning with
#!,
the remainder of the first line specifies an interpreter
for the program. The shell executes the
specified interpreter on operating systems that do not
handle this executable format themselves. The arguments to the
interpreter consist of a single optional argument following the
interpreter name on the first line of the program, followed
by the name of the program, followed by the command
arguments, if any.
COMMAND EXECUTION ENVIRONMENT
The shell has an execution environment, which consists of the
following:
- *
-
open files inherited by the shell at invocation, as modified by
redirections supplied to the exec builtin
- *
-
the current working directory as set by cd, pushd, or
popd, or inherited by the shell at invocation
- *
-
the file creation mode mask as set by umask or inherited from
the shell's parent
- *
-
current traps set by trap
- *
-
shell parameters that are set by variable assignment or with set
or inherited from the shell's parent in the environment
- *
-
shell functions defined during execution or inherited from the shell's
parent in the environment
- *
-
options enabled at invocation (either by default or with command-line
arguments) or by set
- *
-
options enabled by shopt
- *
-
shell aliases defined with alias
- *
-
various process IDs, including those of background jobs, the value
of $$, and the value of
PPID
When a simple command other than a builtin or shell function
is to be executed, it
is invoked in a separate execution environment that consists of
the following. Unless otherwise noted, the values are inherited
from the shell.
- *
-
the shell's open files, plus any modifications and additions specified
by redirections to the command
- *
-
the current working directory
- *
-
the file creation mode mask
- *
-
shell variables and functions marked for export, along with variables
exported for the command, passed in the environment
- *
-
traps caught by the shell are reset to the values inherited from the
shell's parent, and traps ignored by the shell are ignored
A command invoked in this separate environment cannot affect the
shell's execution environment.
Command substitution, commands grouped with parentheses,
and asynchronous commands are invoked in a
subshell environment that is a duplicate of the shell environment,
except that traps caught by the shell are reset to the values
that the shell inherited from its parent at invocation. Builtin
commands that are invoked as part of a pipeline are also executed in a
subshell environment. Changes made to the subshell environment
cannot affect the shell's execution environment.
Subshells spawned to execute command substitutions inherit the value of
the -e option from the parent shell. When not in posix mode,
bash clears the -e option in such subshells.
If a command is followed by a & and job control is not active, the
default standard input for the command is the empty file /dev/null.
Otherwise, the invoked command inherits the file descriptors of the calling
shell as modified by redirections.
ENVIRONMENT
When a program is invoked it is given an array of strings
called the
environment.
This is a list of
name-value pairs, of the form
name=value.
The shell provides several ways to manipulate the environment.
On invocation, the shell scans its own environment and
creates a parameter for each name found, automatically marking
it for
export
to child processes. Executed commands inherit the environment.
The
export
and
declare -x
commands allow parameters and functions to be added to and
deleted from the environment. If the value of a parameter
in the environment is modified, the new value becomes part
of the environment, replacing the old. The environment
inherited by any executed command consists of the shell's
initial environment, whose values may be modified in the shell,
less any pairs removed by the
unset
command, plus any additions via the
export
and
declare -x
commands.
The environment for any
simple command
or function may be augmented temporarily by prefixing it with
parameter assignments, as described above in
PARAMETERS.
These assignment statements affect only the environment seen
by that command.
If the
-k
option is set (see the
set
builtin command below), then
all
parameter assignments are placed in the environment for a command,
not just those that precede the command name.
When
bash
invokes an external command, the variable
_
is set to the full filename of the command and passed to that
command in its environment.
EXIT STATUS
The exit status of an executed command is the value returned by the
waitpid system call or equivalent function. Exit statuses
fall between 0 and 255, though, as explained below, the shell may
use values above 125 specially. Exit statuses from shell builtins and
compound commands are also limited to this range. Under certain
circumstances, the shell will use special values to indicate specific
failure modes.
For the shell's purposes, a command which exits with a
zero exit status has succeeded. An exit status of zero
indicates success. A non-zero exit status indicates failure.
When a command terminates on a fatal signal N, bash uses
the value of 128+N as the exit status.
If a command is not found, the child process created to
execute it returns a status of 127. If a command is found
but is not executable, the return status is 126.
If a command fails because of an error during expansion or redirection,
the exit status is greater than zero.
Shell builtin commands return a status of 0 (true) if
successful, and non-zero (false) if an error occurs
while they execute.
All builtins return an exit status of 2 to indicate incorrect usage.
Bash itself returns the exit status of the last command
executed, unless a syntax error occurs, in which case it exits
with a non-zero value. See also the exit builtin
command below.
SIGNALS
When bash is interactive, in the absence of any traps, it ignores
SIGTERM
(so that kill 0 does not kill an interactive shell),
and
SIGINT
is caught and handled (so that the wait builtin is interruptible).
In all cases, bash ignores
SIGQUIT.
If job control is in effect,
bash
ignores
SIGTTIN,
SIGTTOU,
and
SIGTSTP.
Non-builtin commands run by bash have signal handlers
set to the values inherited by the shell from its parent.
When job control is not in effect, asynchronous commands
ignore
SIGINT
and
SIGQUIT
in addition to these inherited handlers.
Commands run as a result of command substitution ignore the
keyboard-generated job control signals
SIGTTIN,
SIGTTOU,
and
SIGTSTP.
The shell exits by default upon receipt of a
SIGHUP.
Before exiting, an interactive shell resends the
SIGHUP
to all jobs, running or stopped.
Stopped jobs are sent
SIGCONT
to ensure that they receive the
SIGHUP.
To prevent the shell from
sending the signal to a particular job, it should be removed from the
jobs table with the
disown
builtin (see
SHELL BUILTIN COMMANDS
below) or marked
to not receive
SIGHUP
using
disown -h.
If the
huponexit
shell option has been set with
shopt,
bash
sends a
SIGHUP
to all jobs when an interactive login shell exits.
If bash is waiting for a command to complete and receives a signal
for which a trap has been set, the trap will not be executed until
the command completes.
When bash is waiting for an asynchronous command via the wait
builtin, the reception of a signal for which a trap has been set will
cause the wait builtin to return immediately with an exit status
greater than 128, immediately after which the trap is executed.
JOB CONTROL
Job control
refers to the ability to selectively stop (suspend)
the execution of processes and continue (resume)
their execution at a later point. A user typically employs
this facility via an interactive interface supplied jointly
by the operating system kernel's terminal driver and
bash.
The shell associates a
job
with each pipeline. It keeps a table of currently executing
jobs, which may be listed with the
jobs
command. When
bash
starts a job asynchronously (in the
background),
it prints a line that looks like:
-
[1] 25647
indicating that this job is job number 1 and that the process ID
of the last process in the pipeline associated with this job is 25647.
All of the processes in a single pipeline are members of the same job.
Bash
uses the
job
abstraction as the basis for job control.
To facilitate the implementation of the user interface to job
control, the operating system maintains the notion of a current terminal
process group ID. Members of this process group (processes whose
process group ID is equal to the current terminal process group ID)
receive keyboard-generated signals such as
SIGINT.
These processes are said to be in the
foreground.
Background
processes are those whose process group ID differs from the terminal's;
such processes are immune to keyboard-generated signals.
Only foreground processes are allowed to read from or, if the
user so specifies with stty tostop, write to the
terminal.
Background processes which attempt to read from (write to when
stty tostop is in effect) the
terminal are sent a
SIGTTIN (SIGTTOU)
signal by the kernel's terminal driver,
which, unless caught, suspends the process.
If the operating system on which
bash
is running supports
job control,
bash
contains facilities to use it.
Typing the
suspend
character (typically
^Z,
Control-Z) while a process is running
causes that process to be stopped and returns control to
bash.
Typing the
delayed suspend
character (typically
^Y,
Control-Y) causes the process to be stopped when it
attempts to read input from the terminal, and control to
be returned to
bash.
The user may then manipulate the state of this job, using the
bg
command to continue it in the background, the
fg
command to continue it in the foreground, or
the
kill
command to kill it. A ^Z takes effect immediately,
and has the additional side effect of causing pending output
and typeahead to be discarded.
There are a number of ways to refer to a job in the shell.
The character
%
introduces a job specification (jobspec). Job number
n
may be referred to as
%n.
A job may also be referred to using a prefix of the name used to
start it, or using a substring that appears in its command line.
For example,
%ce
refers to a stopped
ce
job. If a prefix matches more than one job,
bash
reports an error. Using
%?ce,
on the other hand, refers to any job containing the string
ce
in its command line. If the substring matches more than one job,
bash
reports an error. The symbols
%%
and
%+
refer to the shell's notion of the
current job,
which is the last job stopped while it was in
the foreground or started in the background.
The
previous job
may be referenced using
%-.
If there is only a single job, %+ and %- can both be used
to refer to that job.
In output pertaining to jobs (e.g., the output of the
jobs
command), the current job is always flagged with a
+,
and the previous job with a
-.
A single % (with no accompanying job specification) also refers to the
current job.
Simply naming a job can be used to bring it into the
foreground:
%1
is a synonym for
``fg %1'',
bringing job 1 from the background into the foreground.
Similarly,
``%1 &''
resumes job 1 in the background, equivalent to
``bg %1''.
The shell learns immediately whenever a job changes state.
Normally,
bash
waits until it is about to print a prompt before reporting
changes in a job's status so as to not interrupt
any other output. If the
-b
option to the
set
builtin command
is enabled,
bash
reports such changes immediately.
Any trap on
SIGCHLD
is executed for each child that exits.
If an attempt to exit
bash
is made while jobs are stopped (or, if the checkjobs shell option has
been enabled using the shopt builtin, running), the shell prints a
warning message, and, if the checkjobs option is enabled, lists the
jobs and their statuses.
The
jobs
command may then be used to inspect their status.
If a second attempt to exit is made without an intervening command,
the shell does not print another warning, and any stopped
jobs are terminated.
PROMPTING
When executing interactively,
bash
displays the primary prompt
PS1
when it is ready to read a command, and the secondary prompt
PS2
when it needs more input to complete a command.
Bash
allows these prompt strings to be customized by inserting a number of
backslash-escaped special characters that are decoded as follows:
-
- \a
-
an ASCII bell character (07)
- \d
-
the date in "Weekday Month Date" format (e.g., "Tue May 26")
- \D{format}
-
the format is passed to strftime(3) and the result is inserted
into the prompt string; an empty format results in a locale-specific
time representation. The braces are required
- \e
-
an ASCII escape character (033)
- \h
-
the hostname up to the first `.'
- \H
-
the hostname
- \j
-
the number of jobs currently managed by the shell
- \l
-
the basename of the shell's terminal device name
- \n
-
newline
- \r
-
carriage return
- \s
-
the name of the shell, the basename of
$0
(the portion following the final slash)
- \t
-
the current time in 24-hour HH:MM:SS format
- \T
-
the current time in 12-hour HH:MM:SS format
- \@
-
the current time in 12-hour am/pm format
- \A
-
the current time in 24-hour HH:MM format
- \u
-
the username of the current user
- \v
-
the version of bash (e.g., 2.00)
- \V
-
the release of bash, version + patch level (e.g., 2.00.0)
- \w
-
the current working directory, with
$HOME
abbreviated with a tilde
(uses the value of the
PROMPT_DIRTRIM
variable)
- \W
-
the basename of the current working directory, with
$HOME
abbreviated with a tilde
- \!
-
the history number of this command
- \#
-
the command number of this command
- \$
-
if the effective UID is 0, a
#,
otherwise a
$
- \nnn
-
the character corresponding to the octal number nnn
- \\
-
a backslash
- \[
-
begin a sequence of non-printing characters, which could be used to
embed a terminal control sequence into the prompt
- \]
-
end a sequence of non-printing characters
The command number and the history number are usually different:
the history number of a command is its position in the history
list, which may include commands restored from the history file
(see
HISTORY
below), while the command number is the position in the sequence
of commands executed during the current shell session.
After the string is decoded, it is expanded via
parameter expansion, command substitution, arithmetic
expansion, and quote removal, subject to the value of the
promptvars
shell option (see the description of the
shopt
command under
SHELL BUILTIN COMMANDS
below).
READLINE
This is the library that handles reading input when using an interactive
shell, unless the
--noediting
option is given at shell invocation.
Line editing is also used when using the -e option to the
read builtin.
By default, the line editing commands are similar to those of Emacs.
A vi-style line editing interface is also available.
Line editing can be enabled at any time using the
-o emacs
or
-o vi
options to the
set
builtin (see
SHELL BUILTIN COMMANDS
below).
To turn off line editing after the shell is running, use the
+o emacs
or
+o vi
options to the
set
builtin.
Readline Notation
In this section, the Emacs-style notation is used to denote
keystrokes. Control keys are denoted by C-key, e.g., C-n
means Control-N. Similarly,
meta
keys are denoted by M-key, so M-x means Meta-X. (On keyboards
without a
meta
key, M-x means ESC x, i.e., press the Escape key
then the
x
key. This makes ESC the meta prefix.
The combination M-C-x means ESC-Control-x,
or press the Escape key
then hold the Control key while pressing the
x
key.)
Readline commands may be given numeric
arguments,
which normally act as a repeat count.
Sometimes, however, it is the sign of the argument that is significant.
Passing a negative argument to a command that acts in the forward
direction (e.g., kill-line) causes that command to act in a
backward direction.
Commands whose behavior with arguments deviates from this are noted
below.
When a command is described as killing text, the text
deleted is saved for possible future retrieval
(yanking). The killed text is saved in a
kill ring. Consecutive kills cause the text to be
accumulated into one unit, which can be yanked all at once.
Commands which do not kill text separate the chunks of text
on the kill ring.
Readline Initialization
Readline is customized by putting commands in an initialization
file (the inputrc file).
The name of this file is taken from the value of the
INPUTRC
variable. If that variable is unset, the default is
~/.inputrc.
When a program which uses the readline library starts up, the
initialization file is read, and the key bindings and variables
are set.
There are only a few basic constructs allowed in the
readline initialization file.
Blank lines are ignored.
Lines beginning with a # are comments.
Lines beginning with a $ indicate conditional constructs.
Other lines denote key bindings and variable settings.
The default key-bindings may be changed with an
inputrc
file.
Other programs that use this library may add their own commands
and bindings.
For example, placing
-
M-Control-u: universal-argument
or
-
C-Meta-u: universal-argument
into the
inputrc
would make M-C-u execute the readline command
universal-argument.
The following symbolic character names are recognized:
RUBOUT,
DEL,
ESC,
LFD,
NEWLINE,
RET,
RETURN,
SPC,
SPACE,
and
TAB.
In addition to command names, readline allows keys to be bound
to a string that is inserted when the key is pressed (a macro).
Readline Key Bindings
The syntax for controlling key bindings in the
inputrc
file is simple. All that is required is the name of the
command or the text of a macro and a key sequence to which
it should be bound. The name may be specified in one of two ways:
as a symbolic key name, possibly with Meta- or Control-
prefixes, or as a key sequence.
When using the form keyname:function-name or macro,
keyname
is the name of a key spelled out in English. For example:
-
Control-u: universal-argument
Meta-Rubout: backward-kill-word
Control-o: "> output"
In the above example,
C-u
is bound to the function
universal-argument,
M-DEL
is bound to the function
backward-kill-word,
and
C-o
is bound to run the macro
expressed on the right hand side (that is, to insert the text
> output
into the line).
In the second form, "keyseq":function-name or macro,
keyseq
differs from
keyname
above in that strings denoting
an entire key sequence may be specified by placing the sequence
within double quotes. Some GNU Emacs style key escapes can be
used, as in the following example, but the symbolic character names
are not recognized.
-
"\C-u": universal-argument
"\C-x\C-r": re-read-init-file
"\e[11~": "Function Key 1"
In this example,
C-u
is again bound to the function
universal-argument.
C-x C-r
is bound to the function
re-read-init-file,
and
ESC [ 1 1 ~
is bound to insert the text
Function Key 1.
The full set of GNU Emacs style escape sequences is
-
- \C-
-
control prefix
- \M-
-
meta prefix
- \e
-
an escape character
- \\
-
backslash
- \
-
literal "
- \aq
-
literal aq
In addition to the GNU Emacs style escape sequences, a second
set of backslash escapes is available:
-
- \a
-
alert (bell)
- \b
-
backspace
- \d
-
delete
- \f
-
form feed
- \n
-
newline
- \r
-
carriage return
- \t
-
horizontal tab
- \v
-
vertical tab
- \nnn
-
the eight-bit character whose value is the octal value nnn
(one to three digits)
- \xHH
-
the eight-bit character whose value is the hexadecimal value HH
(one or two hex digits)
When entering the text of a macro, single or double quotes must
be used to indicate a macro definition.
Unquoted text is assumed to be a function name.
In the macro body, the backslash escapes described above are expanded.
Backslash will quote any other character in the macro text,
including " and aq.
Bash
allows the current readline key bindings to be displayed or modified
with the
bind
builtin command. The editing mode may be switched during interactive
use by using the
-o
option to the
set
builtin command (see
SHELL BUILTIN COMMANDS
below).
Readline Variables
Readline has variables that can be used to further customize its
behavior. A variable may be set in the
inputrc
file with a statement of the form
-
set variable-name value
Except where noted, readline variables can take the values
On
or
Off
(without regard to case).
Unrecognized variable names are ignored.
When a variable value is read, empty or null values, "on" (case-insensitive),
and "1" are equivalent to On. All other values are equivalent to
Off.
The variables and their default values are:
- bell-style (audible)
-
Controls what happens when readline wants to ring the terminal bell.
If set to none, readline never rings the bell. If set to
visible, readline uses a visible bell if one is available.
If set to audible, readline attempts to ring the terminal's bell.
- bind-tty-special-chars (On)
-
If set to On, readline attempts to bind the control characters
treated specially by the kernel's terminal driver to their readline
equivalents.
- colored-stats (Off)
-
If set to On, readline displays possible completions using different
colors to indicate their file type.
The color definitions are taken from the value of the LS_COLORS
environment variable.
- comment-begin (``#'')
-
The string that is inserted when the readline
insert-comment
command is executed.
This command is bound to
M-#
in emacs mode and to
#
in vi command mode.
- completion-ignore-case (Off)
-
If set to On, readline performs filename matching and completion
in a case-insensitive fashion.
- completion-prefix-display-length (0)
-
The length in characters of the common prefix of a list of possible
completions that is displayed without modification. When set to a
value greater than zero, common prefixes longer than this value are
replaced with an ellipsis when displaying possible completions.
- completion-query-items (100)
-
This determines when the user is queried about viewing
the number of possible completions
generated by the possible-completions command.
It may be set to any integer value greater than or equal to
zero. If the number of possible completions is greater than
or equal to the value of this variable, the user is asked whether
or not he wishes to view them; otherwise they are simply listed
on the terminal.
- convert-meta (On)
-
If set to On, readline will convert characters with the
eighth bit set to an ASCII key sequence
by stripping the eighth bit and prefixing an
escape character (in effect, using escape as the meta prefix).
- disable-completion (Off)
-
If set to On, readline will inhibit word completion. Completion
characters will be inserted into the line as if they had been
mapped to self-insert.
- editing-mode (emacs)
-
Controls whether readline begins with a set of key bindings similar
to Emacs or vi.
editing-mode
can be set to either
emacs
or
vi.
- echo-control-characters (On)
-
When set to On, on operating systems that indicate they support it,
readline echoes a character corresponding to a signal generated from the
keyboard.
- enable-keypad (Off)
-
When set to On, readline will try to enable the application
keypad when it is called. Some systems need this to enable the
arrow keys.
- enable-meta-key (On)
-
When set to On, readline will try to enable any meta modifier
key the terminal claims to support when it is called. On many terminals,
the meta key is used to send eight-bit characters.
- expand-tilde (Off)
-
If set to On, tilde expansion is performed when readline
attempts word completion.
- history-preserve-point (Off)
-
If set to On, the history code attempts to place point at the
same location on each history line retrieved with previous-history
or next-history.
- history-size (0)
-
Set the maximum number of history entries saved in the history list.
If set to zero, any existing history entries are deleted and no new entries
are saved.
If set to a value less than zero, the number of history entries is not
limited.
By default, the number of history entries is not limited.
- horizontal-scroll-mode (Off)
-
When set to On, makes readline use a single line for display,
scrolling the input horizontally on a single screen line when it
becomes longer than the screen width rather than wrapping to a new line.
- input-meta (Off)
-
If set to On, readline will enable eight-bit input (that is,
it will not strip the high bit from the characters it reads),
regardless of what the terminal claims it can support. The name
meta-flag
is a synonym for this variable.
- isearch-terminators (``C-[C-J'')
-
The string of characters that should terminate an incremental
search without subsequently executing the character as a command.
If this variable has not been given a value, the characters
ESC and C-J will terminate an incremental search.
- keymap (emacs)
-
Set the current readline keymap. The set of valid keymap names is
emacs, emacs-standard, emacs-meta, emacs-ctlx, vi,
vi-command, and
vi-insert.
vi is equivalent to vi-command; emacs is
equivalent to emacs-standard. The default value is
emacs;
the value of
editing-mode
also affects the default keymap.
- keyseq-timeout (500)
-
Specifies the duration readline will wait for a character when reading an
ambiguous key sequence (one that can form a complete key sequence using
the input read so far, or can take additional input to complete a longer
key sequence).
If no input is received within the timeout, readline will use the shorter
but complete key sequence.
The value is specified in milliseconds, so a value of 1000 means that
readline will wait one second for additional input.
If this variable is set to a value less than or equal to zero, or to a
non-numeric value, readline will wait until another key is pressed to
decide which key sequence to complete.
- mark-directories (On)
-
If set to On, completed directory names have a slash
appended.
- mark-modified-lines (Off)
-
If set to On, history lines that have been modified are displayed
with a preceding asterisk (*).
- mark-symlinked-directories (Off)
-
If set to On, completed names which are symbolic links to directories
have a slash appended (subject to the value of
mark-directories).
- match-hidden-files (On)
-
This variable, when set to On, causes readline to match files whose
names begin with a `.' (hidden files) when performing filename
completion.
If set to Off, the leading `.' must be
supplied by the user in the filename to be completed.
- menu-complete-display-prefix (Off)
-
If set to On, menu completion displays the common prefix of the
list of possible completions (which may be empty) before cycling through
the list.
- output-meta (Off)
-
If set to On, readline will display characters with the
eighth bit set directly rather than as a meta-prefixed escape
sequence.
- page-completions (On)
-
If set to On, readline uses an internal more-like pager
to display a screenful of possible completions at a time.
- print-completions-horizontally (Off)
-
If set to On, readline will display completions with matches
sorted horizontally in alphabetical order, rather than down the screen.
- revert-all-at-newline (Off)
-
If set to On, readline will undo all changes to history lines
before returning when accept-line is executed. By default,
history lines may be modified and retain individual undo lists across
calls to readline.
- show-all-if-ambiguous (Off)
-
This alters the default behavior of the completion functions. If
set to
On,
words which have more than one possible completion cause the
matches to be listed immediately instead of ringing the bell.
- show-all-if-unmodified (Off)
-
This alters the default behavior of the completion functions in
a fashion similar to show-all-if-ambiguous.
If set to
On,
words which have more than one possible completion without any
possible partial completion (the possible completions don't share
a common prefix) cause the matches to be listed immediately instead
of ringing the bell.
- show-mode-in-prompt (Off)
-
If set to On, add a character to the beginning of the prompt
indicating the editing mode: emacs (@), vi command (:) or vi
insertion (+).
- skip-completed-text (Off)
-
If set to On, this alters the default completion behavior when
inserting a single match into the line. It's only active when
performing completion in the middle of a word. If enabled, readline
does not insert characters from the completion that match characters
after point in the word being completed, so portions of the word
following the cursor are not duplicated.
- visible-stats (Off)
-
If set to On, a character denoting a file's type as reported
by stat(2) is appended to the filename when listing possible
completions.
Readline Conditional Constructs
Readline implements a facility similar in spirit to the conditional
compilation features of the C preprocessor which allows key
bindings and variable settings to be performed as the result
of tests. There are four parser directives used.
- $if
-
The
$if
construct allows bindings to be made based on the
editing mode, the terminal being used, or the application using
readline. The text of the test extends to the end of the line;
no characters are required to isolate it.
-
- mode
-
The mode= form of the $if directive is used to test
whether readline is in emacs or vi mode.
This may be used in conjunction
with the set keymap command, for instance, to set bindings in
the emacs-standard and emacs-ctlx keymaps only if
readline is starting out in emacs mode.
- term
-
The term= form may be used to include terminal-specific
key bindings, perhaps to bind the key sequences output by the
terminal's function keys. The word on the right side of the
=
is tested against the both full name of the terminal and the portion
of the terminal name before the first -. This allows
sun
to match both
sun
and
sun-cmd,
for instance.
- application
-
The application construct is used to include
application-specific settings. Each program using the readline
library sets the application name, and an initialization
file can test for a particular value.
This could be used to bind key sequences to functions useful for
a specific program. For instance, the following command adds a
key sequence that quotes the current or previous word in bash:
-
$if Bash
# Quote the current or previous word
"\C-xq": "\eb\"\ef\""
$endif
- $endif
-
This command, as seen in the previous example, terminates an
$if command.
- $else
-
Commands in this branch of the $if directive are executed if
the test fails.
- $include
-
This directive takes a single filename as an argument and reads commands
and bindings from that file. For example, the following directive
would read /etc/inputrc:
-
$include /etc/inputrc
Searching
Readline provides commands for searching through the command history
(see
HISTORY
below) for lines containing a specified string.
There are two search modes:
incremental
and
non-incremental.
Incremental searches begin before the user has finished typing the
search string.
As each character of the search string is typed, readline displays
the next entry from the history matching the string typed so far.
An incremental search requires only as many characters as needed to
find the desired history entry.
The characters present in the value of the isearch-terminators
variable are used to terminate an incremental search.
If that variable has not been assigned a value the Escape and
Control-J characters will terminate an incremental search.
Control-G will abort an incremental search and restore the original
line.
When the search is terminated, the history entry containing the
search string becomes the current line.
To find other matching entries in the history list, type Control-S or
Control-R as appropriate.
This will search backward or forward in the history for the next
entry matching the search string typed so far.
Any other key sequence bound to a readline command will terminate
the search and execute that command.
For instance, a newline will terminate the search and accept
the line, thereby executing the command from the history list.
Readline remembers the last incremental search string. If two
Control-Rs are typed without any intervening characters defining a
new search string, any remembered search string is used.
Non-incremental searches read the entire search string before starting
to search for matching history lines. The search string may be
typed by the user or be part of the contents of the current line.
Readline Command Names
The following is a list of the names of the commands and the default
key sequences to which they are bound.
Command names without an accompanying key sequence are unbound by default.
In the following descriptions, point refers to the current cursor
position, and mark refers to a cursor position saved by the
set-mark command.
The text between the point and mark is referred to as the region.
Commands for Moving
- beginning-of-line (C-a)
-
Move to the start of the current line.
- end-of-line (C-e)
-
Move to the end of the line.
- forward-char (C-f)
-
Move forward a character.
- backward-char (C-b)
-
Move back a character.
- forward-word (M-f)
-
Move forward to the end of the next word. Words are composed of
alphanumeric characters (letters and digits).
- backward-word (M-b)
-
Move back to the start of the current or previous word.
Words are composed of alphanumeric characters (letters and digits).
- shell-forward-word
-
Move forward to the end of the next word.
Words are delimited by non-quoted shell metacharacters.
- shell-backward-word
-
Move back to the start of the current or previous word.
Words are delimited by non-quoted shell metacharacters.
- clear-screen (C-l)
-
Clear the screen leaving the current line at the top of the screen.
With an argument, refresh the current line without clearing the
screen.
- redraw-current-line
-
Refresh the current line.
Commands for Manipulating the History
- accept-line (Newline, Return)
-
Accept the line regardless of where the cursor is. If this line is
non-empty, add it to the history list according to the state of the
HISTCONTROL
variable. If the line is a modified history
line, then restore the history line to its original state.
- previous-history (C-p)
-
Fetch the previous command from the history list, moving back in
the list.
- next-history (C-n)
-
Fetch the next command from the history list, moving forward in the
list.
- beginning-of-history (M-<)
-
Move to the first line in the history.
- end-of-history (M->)
-
Move to the end of the input history, i.e., the line currently being
entered.
- reverse-search-history (C-r)
-
Search backward starting at the current line and moving `up' through
the history as necessary. This is an incremental search.
- forward-search-history (C-s)
-
Search forward starting at the current line and moving `down' through
the history as necessary. This is an incremental search.
- non-incremental-reverse-search-history (M-p)
-
Search backward through the history starting at the current line
using a non-incremental search for a string supplied by the user.
- non-incremental-forward-search-history (M-n)
-
Search forward through the history using a non-incremental search for
a string supplied by the user.
- history-search-forward
-
Search forward through the history for the string of characters
between the start of the current line and the point.
This is a non-incremental search.
- history-search-backward
-
Search backward through the history for the string of characters
between the start of the current line and the point.
This is a non-incremental search.
- yank-nth-arg (M-C-y)
-
Insert the first argument to the previous command (usually
the second word on the previous line) at point.
With an argument
n,
insert the nth word from the previous command (the words
in the previous command begin with word 0). A negative argument
inserts the nth word from the end of the previous command.
Once the argument n is computed, the argument is extracted
as if the "!n" history expansion had been specified.
- yank-last-arg (M-., M-_)
-
Insert the last argument to the previous command (the last word of
the previous history entry).
With a numeric argument, behave exactly like yank-nth-arg.
Successive calls to yank-last-arg move back through the history
list, inserting the last word (or the word specified by the argument to
the first call) of each line in turn.
Any numeric argument supplied to these successive calls determines
the direction to move through the history. A negative argument switches
the direction through the history (back or forward).
The history expansion facilities are used to extract the last word,
as if the "!$" history expansion had been specified.
- shell-expand-line (M-C-e)
-
Expand the line as the shell does. This
performs alias and history expansion as well as all of the shell
word expansions. See
HISTORY EXPANSION
below for a description of history expansion.
- history-expand-line (M-^)
-
Perform history expansion on the current line.
See
HISTORY EXPANSION
below for a description of history expansion.
- magic-space
-
Perform history expansion on the current line and insert a space.
See
HISTORY EXPANSION
below for a description of history expansion.
- alias-expand-line
-
Perform alias expansion on the current line.
See
ALIASES
above for a description of alias expansion.
- history-and-alias-expand-line
-
Perform history and alias expansion on the current line.
- insert-last-argument (M-., M-_)
-
A synonym for yank-last-arg.
- operate-and-get-next (C-o)
-
Accept the current line for execution and fetch the next line
relative to the current line from the history for editing. Any
argument is ignored.
- edit-and-execute-command (C-xC-e)
-
Invoke an editor on the current command line, and execute the result as shell
commands.
Bash attempts to invoke
$VISUAL,
$EDITOR,
and emacs as the editor, in that order.
Commands for Changing Text
- end-of-file (usually C-d)
-
The character indicating end-of-file as set, for example, by
stty.
If this character is read when there are no characters
on the line, and point is at the beginning of the line, Readline
interprets it as the end of input and returns
EOF.
- delete-char (C-d)
-
Delete the character at point.
If this function is bound to the
same character as the tty EOF character, as C-d
commonly is, see above for the effects.
- backward-delete-char (Rubout)
-
Delete the character behind the cursor. When given a numeric argument,
save the deleted text on the kill ring.
- forward-backward-delete-char
-
Delete the character under the cursor, unless the cursor is at the
end of the line, in which case the character behind the cursor is
deleted.
- quoted-insert (C-q, C-v)
-
Add the next character typed to the line verbatim. This is
how to insert characters like C-q, for example.
- tab-insert (C-v TAB)
-
Insert a tab character.
- self-insert (a, b, A, 1, !, ...)
-
Insert the character typed.
- transpose-chars (C-t)
-
Drag the character before point forward over the character at point,
moving point forward as well.
If point is at the end of the line, then this transposes
the two characters before point.
Negative arguments have no effect.
- transpose-words (M-t)
-
Drag the word before point past the word after point,
moving point over that word as well.
If point is at the end of the line, this transposes
the last two words on the line.
- upcase-word (M-u)
-
Uppercase the current (or following) word. With a negative argument,
uppercase the previous word, but do not move point.
- downcase-word (M-l)
-
Lowercase the current (or following) word. With a negative argument,
lowercase the previous word, but do not move point.
- capitalize-word (M-c)
-
Capitalize the current (or following) word. With a negative argument,
capitalize the previous word, but do not move point.
- overwrite-mode
-
Toggle overwrite mode. With an explicit positive numeric argument,
switches to overwrite mode. With an explicit non-positive numeric
argument, switches to insert mode. This command affects only
emacs mode; vi mode does overwrite differently.
Each call to readline() starts in insert mode.
In overwrite mode, characters bound to self-insert replace
the text at point rather than pushing the text to the right.
Characters bound to backward-delete-char replace the character
before point with a space. By default, this command is unbound.
Killing and Yanking
- kill-line (C-k)
-
Kill the text from point to the end of the line.
- backward-kill-line (C-x Rubout)
-
Kill backward to the beginning of the line.
- unix-line-discard (C-u)
-
Kill backward from point to the beginning of the line.
The killed text is saved on the kill-ring.
- kill-whole-line
-
Kill all characters on the current line, no matter where point is.
- kill-word (M-d)
-
Kill from point to the end of the current word, or if between
words, to the end of the next word.
Word boundaries are the same as those used by forward-word.
- backward-kill-word (M-Rubout)
-
Kill the word behind point.
Word boundaries are the same as those used by backward-word.
- shell-kill-word (M-d)
-
Kill from point to the end of the current word, or if between
words, to the end of the next word.
Word boundaries are the same as those used by shell-forward-word.
- shell-backward-kill-word (M-Rubout)
-
Kill the word behind point.
Word boundaries are the same as those used by shell-backward-word.
- unix-word-rubout (C-w)
-
Kill the word behind point, using white space as a word boundary.
The killed text is saved on the kill-ring.
- unix-filename-rubout
-
Kill the word behind point, using white space and the slash character
as the word boundaries.
The killed text is saved on the kill-ring.
- delete-horizontal-space (M-\)
-
Delete all spaces and tabs around point.
- kill-region
-
Kill the text in the current region.
- copy-region-as-kill
-
Copy the text in the region to the kill buffer.
- copy-backward-word
-
Copy the word before point to the kill buffer.
The word boundaries are the same as backward-word.
- copy-forward-word
-
Copy the word following point to the kill buffer.
The word boundaries are the same as forward-word.
- yank (C-y)
-
Yank the top of the kill ring into the buffer at point.
- yank-pop (M-y)
-
Rotate the kill ring, and yank the new top. Only works following
yank
or
yank-pop.
Numeric Arguments
- digit-argument (M-0, M-1, ..., M--)
-
Add this digit to the argument already accumulating, or start a new
argument. M-- starts a negative argument.
- universal-argument
-
This is another way to specify an argument.
If this command is followed by one or more digits, optionally with a
leading minus sign, those digits define the argument.
If the command is followed by digits, executing
universal-argument
again ends the numeric argument, but is otherwise ignored.
As a special case, if this command is immediately followed by a
character that is neither a digit or minus sign, the argument count
for the next command is multiplied by four.
The argument count is initially one, so executing this function the
first time makes the argument count four, a second time makes the
argument count sixteen, and so on.
Completing
- complete (TAB)
-
Attempt to perform completion on the text before point.
Bash
attempts completion treating the text as a variable (if the
text begins with $), username (if the text begins with
~), hostname (if the text begins with @), or
command (including aliases and functions) in turn. If none
of these produces a match, filename completion is attempted.
- possible-completions (M-?)
-
List the possible completions of the text before point.
- insert-completions (M-*)
-
Insert all completions of the text before point
that would have been generated by
possible-completions.
- menu-complete
-
Similar to complete, but replaces the word to be completed
with a single match from the list of possible completions.
Repeated execution of menu-complete steps through the list
of possible completions, inserting each match in turn.
At the end of the list of completions, the bell is rung
(subject to the setting of bell-style)
and the original text is restored.
An argument of n moves n positions forward in the list
of matches; a negative argument may be used to move backward
through the list.
This command is intended to be bound to TAB, but is unbound
by default.
- menu-complete-backward
-
Identical to menu-complete, but moves backward through the list
of possible completions, as if menu-complete had been given a
negative argument. This command is unbound by default.
- delete-char-or-list
-
Deletes the character under the cursor if not at the beginning or
end of the line (like delete-char).
If at the end of the line, behaves identically to
possible-completions.
This command is unbound by default.
- complete-filename (M-/)
-
Attempt filename completion on the text before point.
- possible-filename-completions (C-x /)
-
List the possible completions of the text before point,
treating it as a filename.
- complete-username (M-~)
-
Attempt completion on the text before point, treating
it as a username.
- possible-username-completions (C-x ~)
-
List the possible completions of the text before point,
treating it as a username.
- complete-variable (M-$)
-
Attempt completion on the text before point, treating
it as a shell variable.
- possible-variable-completions (C-x $)
-
List the possible completions of the text before point,
treating it as a shell variable.
- complete-hostname (M-@)
-
Attempt completion on the text before point, treating
it as a hostname.
- possible-hostname-completions (C-x @)
-
List the possible completions of the text before point,
treating it as a hostname.
- complete-command (M-!)
-
Attempt completion on the text before point, treating
it as a command name. Command completion attempts to
match the text against aliases, reserved words, shell
functions, shell builtins, and finally executable filenames,
in that order.
- possible-command-completions (C-x !)
-
List the possible completions of the text before point,
treating it as a command name.
- dynamic-complete-history (M-TAB)
-
Attempt completion on the text before point, comparing
the text against lines from the history list for possible
completion matches.
- dabbrev-expand
-
Attempt menu completion on the text before point, comparing
the text against lines from the history list for possible
completion matches.
- complete-into-braces (M-{)
-
Perform filename completion and insert the list of possible completions
enclosed within braces so the list is available to the shell (see
Brace Expansion
above).
Keyboard Macros
- start-kbd-macro (C-x ()
-
Begin saving the characters typed into the current keyboard macro.
- end-kbd-macro (C-x ))
-
Stop saving the characters typed into the current keyboard macro
and store the definition.
- call-last-kbd-macro (C-x e)
-
Re-execute the last keyboard macro defined, by making the characters
in the macro appear as if typed at the keyboard.
- print-last-kbd-macro ()
-
Print the last keyboard macro defined in a format suitable for the
inputrc file.
Miscellaneous
- re-read-init-file (C-x C-r)
-
Read in the contents of the inputrc file, and incorporate
any bindings or variable assignments found there.
- abort (C-g)
-
Abort the current editing command and
ring the terminal's bell (subject to the setting of
bell-style).
- do-uppercase-version (M-a, M-b, M-x, ...)
-
If the metafied character x is lowercase, run the command
that is bound to the corresponding uppercase character.
- prefix-meta (ESC)
-
Metafy the next character typed.
ESC
f
is equivalent to
Meta-f.
- undo (C-_, C-x C-u)
-
Incremental undo, separately remembered for each line.
- revert-line (M-r)
-
Undo all changes made to this line. This is like executing the
undo
command enough times to return the line to its initial state.
- tilde-expand (M-&)
-
Perform tilde expansion on the current word.
- set-mark (C-@, M-<space>)
-
Set the mark to the point. If a
numeric argument is supplied, the mark is set to that position.
- exchange-point-and-mark (C-x C-x)
-
Swap the point with the mark. The current cursor position is set to
the saved position, and the old cursor position is saved as the mark.
- character-search (C-])
-
A character is read and point is moved to the next occurrence of that
character. A negative count searches for previous occurrences.
- character-search-backward (M-C-])
-
A character is read and point is moved to the previous occurrence of that
character. A negative count searches for subsequent occurrences.
- skip-csi-sequence
-
Read enough characters to consume a multi-key sequence such as those
defined for keys like Home and End. Such sequences begin with a
Control Sequence Indicator (CSI), usually ESC-[. If this sequence is
bound to "\[", keys producing such sequences will have no effect
unless explicitly bound to a readline command, instead of inserting
stray characters into the editing buffer. This is unbound by default,
but usually bound to ESC-[.
- insert-comment (M-#)
-
Without a numeric argument, the value of the readline
comment-begin
variable is inserted at the beginning of the current line.
If a numeric argument is supplied, this command acts as a toggle: if
the characters at the beginning of the line do not match the value
of comment-begin, the value is inserted, otherwise
the characters in comment-begin are deleted from the beginning of
the line.
In either case, the line is accepted as if a newline had been typed.
The default value of
comment-begin causes this command to make the current line
a shell comment.
If a numeric argument causes the comment character to be removed, the line
will be executed by the shell.
- glob-complete-word (M-g)
-
The word before point is treated as a pattern for pathname expansion,
with an asterisk implicitly appended. This pattern is used to
generate a list of matching filenames for possible completions.
- glob-expand-word (C-x *)
-
The word before point is treated as a pattern for pathname expansion,
and the list of matching filenames is inserted, replacing the word.
If a numeric argument is supplied, an asterisk is appended before
pathname expansion.
- glob-list-expansions (C-x g)
-
The list of expansions that would have been generated by
glob-expand-word
is displayed, and the line is redrawn.
If a numeric argument is supplied, an asterisk is appended before
pathname expansion.
- dump-functions
-
Print all of the functions and their key bindings to the
readline output stream. If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an inputrc file.
- dump-variables
-
Print all of the settable readline variables and their values to the
readline output stream. If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an inputrc file.
- dump-macros
-
Print all of the readline key sequences bound to macros and the
strings they output. If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an inputrc file.
- display-shell-version (C-x C-v)
-
Display version information about the current instance of
bash.
Programmable Completion
When word completion is attempted for an argument to a command for
which a completion specification (a compspec) has been defined
using the complete builtin (see
SHELL BUILTIN COMMANDS
below), the programmable completion facilities are invoked.
First, the command name is identified.
If the command word is the empty string (completion attempted at the
beginning of an empty line), any compspec defined with
the -E option to complete is used.
If a compspec has been defined for that command, the
compspec is used to generate the list of possible completions for the word.
If the command word is a full pathname, a compspec for the full
pathname is searched for first.
If no compspec is found for the full pathname, an attempt is made to
find a compspec for the portion following the final slash.
If those searches do not result in a compspec, any compspec defined with
the -D option to complete is used as the default.
Once a compspec has been found, it is used to generate the list of
matching words.
If a compspec is not found, the default bash completion as
described above under Completing is performed.
First, the actions specified by the compspec are used.
Only matches which are prefixed by the word being completed are
returned.
When the
-f
or
-d
option is used for filename or directory name completion, the shell
variable
FIGNORE
is used to filter the matches.
Any completions specified by a pathname expansion pattern to the
-G option are generated next.
The words generated by the pattern need not match the word
being completed.
The
GLOBIGNORE
shell variable is not used to filter the matches, but the
FIGNORE
variable is used.
Next, the string specified as the argument to the -W option
is considered.
The string is first split using the characters in the
IFS
special variable as delimiters.
Shell quoting is honored.
Each word is then expanded using
brace expansion, tilde expansion, parameter and variable expansion,
command substitution, and arithmetic expansion,
as described above under
EXPANSION.
The results are split using the rules described above under
Word Splitting.
The results of the expansion are prefix-matched against the word being
completed, and the matching words become the possible completions.
After these matches have been generated, any shell function or command
specified with the -F and -C options is invoked.
When the command or function is invoked, the
COMP_LINE,
COMP_POINT,
COMP_KEY,
and
COMP_TYPE
variables are assigned values as described above under
Shell Variables.
If a shell function is being invoked, the
COMP_WORDS
and
COMP_CWORD
variables are also set.
When the function or command is invoked,
the first argument ($1) is the name of the command whose arguments are
being completed,
the second argument ($2) is the word being completed,
and the third argument ($3) is the word preceding the word being
completed on the current command line.
No filtering of the generated completions against the word being completed
is performed; the function or command has complete freedom in generating
the matches.
Any function specified with -F is invoked first.
The function may use any of the shell facilities, including the
compgen builtin described below, to generate the matches.
It must put the possible completions in the
COMPREPLY
array variable, one per array element.
Next, any command specified with the -C option is invoked
in an environment equivalent to command substitution.
It should print a list of completions, one per line, to the
standard output.
Backslash may be used to escape a newline, if necessary.
After all of the possible completions are generated, any filter
specified with the -X option is applied to the list.
The filter is a pattern as used for pathname expansion; a &
in the pattern is replaced with the text of the word being completed.
A literal & may be escaped with a backslash; the backslash
is removed before attempting a match.
Any completion that matches the pattern will be removed from the list.
A leading ! negates the pattern; in this case any completion
not matching the pattern will be removed.
Finally, any prefix and suffix specified with the -P and -S
options are added to each member of the completion list, and the result is
returned to the readline completion code as the list of possible
completions.
If the previously-applied actions do not generate any matches, and the
-o dirnames option was supplied to complete when the
compspec was defined, directory name completion is attempted.
If the -o plusdirs option was supplied to complete when the
compspec was defined, directory name completion is attempted and any
matches are added to the results of the other actions.
By default, if a compspec is found, whatever it generates is returned
to the completion code as the full set of possible completions.
The default bash completions are not attempted, and the readline
default of filename completion is disabled.
If the -o bashdefault option was supplied to complete when
the compspec was defined, the bash default completions are attempted
if the compspec generates no matches.
If the -o default option was supplied to complete when the
compspec was defined, readline's default completion will be performed
if the compspec (and, if attempted, the default bash completions)
generate no matches.
When a compspec indicates that directory name completion is desired,
the programmable completion functions force readline to append a slash
to completed names which are symbolic links to directories, subject to
the value of the mark-directories readline variable, regardless
of the setting of the mark-symlinked-directories readline variable.
There is some support for dynamically modifying completions. This is
most useful when used in combination with a default completion specified
with complete -D.
It's possible for shell functions executed as completion
handlers to indicate that completion should be retried by returning an
exit status of 124. If a shell function returns 124, and changes
the compspec associated with the command on which completion is being
attempted (supplied as the first argument when the function is executed),
programmable completion restarts from the beginning, with an
attempt to find a new compspec for that command. This allows a set of
completions to be built dynamically as completion is attempted, rather than
being loaded all at once.
For instance, assuming that there is a library of compspecs, each kept in a
file corresponding to the name of the command, the following default
completion function would load completions dynamically:
_completion_loader()
{
. "/etc/bash_completion.d/$1.sh" >/dev/null 2>&1 && return 124
}
complete -D -F _completion_loader -o bashdefault -o default
HISTORY
When the
-o history
option to the
set
builtin is enabled, the shell provides access to the
command history,
the list of commands previously typed.
The value of the
HISTSIZE
variable is used as the
number of commands to save in a history list.
The text of the last
HISTSIZE
commands (default 500) is saved. The shell
stores each command in the history list prior to parameter and
variable expansion (see
EXPANSION
above) but after history expansion is performed, subject to the
values of the shell variables
HISTIGNORE
and
HISTCONTROL.
On startup, the history is initialized from the file named by
the variable
HISTFILE
(default ~/.bash_history).
The file named by the value of
HISTFILE
is truncated, if necessary, to contain no more than
the number of lines specified by the value of
HISTFILESIZE.
If HISTFILESIZE is unset, or set to null, a non-numeric value,
or a numeric value less than zero, the history file is not truncated.
When the history file is read,
lines beginning with the history comment character followed immediately
by a digit are interpreted as timestamps for the preceding history line.
These timestamps are optionally displayed depending on the value of the
HISTTIMEFORMAT
variable.
When a shell with history enabled exits, the last
$HISTSIZE
lines are copied from the history list to
$HISTFILE.
If the
histappend
shell option is enabled
(see the description of
shopt
under
SHELL BUILTIN COMMANDS
below), the lines are appended to the history file,
otherwise the history file is overwritten.
If
HISTFILE
is unset, or if the history file is unwritable, the history is
not saved.
If the
HISTTIMEFORMAT
variable is set, time stamps are written to the history file, marked
with the history comment character, so
they may be preserved across shell sessions.
This uses the history comment character to distinguish timestamps from
other history lines.
After saving the history, the history file is truncated
to contain no more than
HISTFILESIZE
lines. If
HISTFILESIZE
is unset, or set to null, a non-numeric value,
or a numeric value less than zero, the history file is not truncated.
The builtin command
fc
(see
SHELL BUILTIN COMMANDS
below) may be used to list or edit and re-execute a portion of
the history list.
The
history
builtin may be used to display or modify the history list and
manipulate the history file.
When using command-line editing, search commands
are available in each editing mode that provide access to the
history list.
The shell allows control over which commands are saved on the history
list. The
HISTCONTROL
and
HISTIGNORE
variables may be set to cause the shell to save only a subset of the
commands entered.
The
cmdhist
shell option, if enabled, causes the shell to attempt to save each
line of a multi-line command in the same history entry, adding
semicolons where necessary to preserve syntactic correctness.
The
lithist
shell option causes the shell to save the command with embedded newlines
instead of semicolons. See the description of the
shopt
builtin below under
SHELL BUILTIN COMMANDS
for information on setting and unsetting shell options.
HISTORY EXPANSION
The shell supports a history expansion feature that
is similar to the history expansion in
csh.
This section describes what syntax features are available. This
feature is enabled by default for interactive shells, and can be
disabled using the
+H
option to the
set
builtin command (see
SHELL BUILTIN COMMANDS
below). Non-interactive shells do not perform history expansion
by default.
History expansions introduce words from the history list into
the input stream, making it easy to repeat commands, insert the
arguments to a previous command into the current input line, or
fix errors in previous commands quickly.
History expansion is performed immediately after a complete line
is read, before the shell breaks it into words.
It takes place in two parts.
The first is to determine which line from the history list
to use during substitution.
The second is to select portions of that line for inclusion into
the current one.
The line selected from the history is the event,
and the portions of that line that are acted upon are words.
Various modifiers are available to manipulate the selected words.
The line is broken into words in the same fashion as when reading input,
so that several metacharacter-separated words surrounded by
quotes are considered one word.
History expansions are introduced by the appearance of the
history expansion character, which is ! by default.
Only backslash (\) and single quotes can quote
the history expansion character.
Several characters inhibit history expansion if found immediately
following the history expansion character, even if it is unquoted:
space, tab, newline, carriage return, and =.
If the extglob shell option is enabled, ( will also
inhibit expansion.
Several shell options settable with the
shopt
builtin may be used to tailor the behavior of history expansion.
If the
histverify
shell option is enabled (see the description of the
shopt
builtin below), and
readline
is being used, history substitutions are not immediately passed to
the shell parser.
Instead, the expanded line is reloaded into the
readline
editing buffer for further modification.
If
readline
is being used, and the
histreedit
shell option is enabled, a failed history substitution will be reloaded
into the
readline
editing buffer for correction.
The
-p
option to the
history
builtin command may be used to see what a history expansion will
do before using it.
The
-s
option to the
history
builtin may be used to add commands to the end of the history list
without actually executing them, so that they are available for
subsequent recall.
The shell allows control of the various characters used by the
history expansion mechanism (see the description of
histchars
above under
Shell Variables).
The shell uses
the history comment character to mark history timestamps when
writing the history file.
Event Designators
An event designator is a reference to a command line entry in the
history list.
Unless the reference is absolute, events are relative to the current
position in the history list.
- !
-
Start a history substitution, except when followed by a
blank,
newline, carriage return, =
or ( (when the extglob shell option is enabled using
the shopt builtin).
- !n
-
Refer to command line
n.
- !-n
-
Refer to the current command minus
n.
- !!
-
Refer to the previous command. This is a synonym for `!-1'.
- !string
-
Refer to the most recent command preceding the current position in the
history list starting with
string.
- !?string[?]
-
Refer to the most recent command preceding the current position in the
history list containing
string.
The trailing ? may be omitted if
string
is followed immediately by a newline.
- ^string1^string2^
-
Quick substitution. Repeat the previous command, replacing
string1
with
string2.
Equivalent to
``!!:s/string1/string2/''
(see Modifiers below).
- !#
-
The entire command line typed so far.
Word Designators
Word designators are used to select desired words from the event.
A
:
separates the event specification from the word designator.
It may be omitted if the word designator begins with a
^,
$,
*,
-,
or
%.
Words are numbered from the beginning of the line,
with the first word being denoted by 0 (zero).
Words are inserted into the current line separated by single spaces.
- 0 (zero)
-
The zeroth word. For the shell, this is the command
word.
- n
-
The nth word.
- ^
-
The first argument. That is, word 1.
- $
-
The last word. This is usually the last argument, but will expand to the
zeroth word if there is only one word in the line.
- %
-
The word matched by the most recent `?string?' search.
- x-y
-
A range of words; `-y' abbreviates `0-y'.
- *
-
All of the words but the zeroth. This is a synonym
for `1-$'. It is not an error to use
*
if there is just one
word in the event; the empty string is returned in that case.
- x*
-
Abbreviates x-$.
- x-
-
Abbreviates x-$ like x*, but omits the last word.
If a word designator is supplied without an event specification, the
previous command is used as the event.
Modifiers
After the optional word designator, there may appear a sequence of
one or more of the following modifiers, each preceded by a `:'.
- h
-
Remove a trailing filename component, leaving only the head.
- t
-
Remove all leading filename components, leaving the tail.
- r
-
Remove a trailing suffix of the form .xxx, leaving the
basename.
- e
-
Remove all but the trailing suffix.
- p
-
Print the new command but do not execute it.
- q
-
Quote the substituted words, escaping further substitutions.
- x
-
Quote the substituted words as with
q,
but break into words at
blanks
and newlines.
- s/old/new/
-
Substitute
new
for the first occurrence of
old
in the event line. Any delimiter can be used in place of /. The
final delimiter is optional if it is the last character of the
event line. The delimiter may be quoted in
old
and
new
with a single backslash. If & appears in
new,
it is replaced by
old.
A single backslash will quote the &. If
old
is null, it is set to the last
old
substituted, or, if no previous history substitutions took place,
the last
string
in a
!?string[?]
search.
- &
-
Repeat the previous substitution.
- g
-
Cause changes to be applied over the entire event line. This is
used in conjunction with `:s' (e.g., `:gs/old/new/')
or `:&'. If used with
`:s', any delimiter can be used
in place of /, and the final delimiter is optional
if it is the last character of the event line.
An a may be used as a synonym for g.
- G
-
Apply the following `s' modifier once to each word in the event line.
SHELL BUILTIN COMMANDS
Unless otherwise noted, each builtin command documented in this
section as accepting options preceded by
-
accepts
--
to signify the end of the options.
The :, true, false, and test builtins
do not accept options and do not treat -- specially.
The exit, logout, break, continue, let,
and shift builtins accept and process arguments beginning with
- without requiring --.
Other builtins that accept arguments but are not specified as accepting
options interpret arguments beginning with - as invalid options and
require -- to prevent this interpretation.
- : [arguments]
-
No effect; the command does nothing beyond expanding
arguments
and performing any specified
redirections. A zero exit code is returned.
- . filename [arguments]
-
- source filename [arguments]
-
Read and execute commands from
filename
in the current
shell environment and return the exit status of the last command
executed from
filename.
If
filename
does not contain a slash, filenames in
PATH
are used to find the directory containing
filename.
The file searched for in
PATH
need not be executable.
When bash is not in posix mode, the current directory is
searched if no file is found in
PATH.
If the
sourcepath
option to the
shopt
builtin command is turned off, the
PATH
is not searched.
If any arguments are supplied, they become the positional
parameters when filename is executed. Otherwise the positional
parameters are unchanged.
The return status is the status of the last command exited within
the script (0 if no commands are executed), and false if
filename
is not found or cannot be read.
- alias [-p] [name[=value] ...]
-
Alias with no arguments or with the
-p
option prints the list of aliases in the form
alias name=value on standard output.
When arguments are supplied, an alias is defined for
each name whose value is given.
A trailing space in value causes the next word to be
checked for alias substitution when the alias is expanded.
For each name in the argument list for which no value
is supplied, the name and value of the alias is printed.
Alias returns true unless a name is given for which
no alias has been defined.
- bg [jobspec ...]
-
Resume each suspended job jobspec in the background, as if it
had been started with
&.
If
jobspec
is not present, the shell's notion of the current job is used.
bg
jobspec
returns 0 unless run when job control is disabled or, when run with
job control enabled, any specified jobspec was not found
or was started without job control.
- bind [-m keymap] [-lpsvPSVX]
-
- bind [-m keymap] [-q function] [-u function] [-r keyseq]
-
- bind [-m keymap] -f filename
-
- bind [-m keymap] -x keyseq:shell-command
-
- bind [-m keymap] keyseq:function-name
-
- bind readline-command
-
Display current
readline
key and function bindings, bind a key sequence to a
readline
function or macro, or set a
readline
variable.
Each non-option argument is a command as it would appear in
.inputrc,
but each binding or command must be passed as a separate argument;
e.g., '"\C-x\C-r": re-read-init-file'.
Options, if supplied, have the following meanings:
-
- -m keymap
-
Use
keymap
as the keymap to be affected by the subsequent bindings.
Acceptable
keymap
names are
emacs, emacs-standard, emacs-meta, emacs-ctlx, vi,
vi-move, vi-command, and
vi-insert.
vi is equivalent to vi-command; emacs is
equivalent to emacs-standard.
- -l
-
List the names of all readline functions.
- -p
-
Display readline function names and bindings in such a way
that they can be re-read.
- -P
-
List current readline function names and bindings.
- -s
-
Display readline key sequences bound to macros and the strings
they output in such a way that they can be re-read.
- -S
-
Display readline key sequences bound to macros and the strings
they output.
- -v
-
Display readline variable names and values in such a way that they
can be re-read.
- -V
-
List current readline variable names and values.
- -f filename
-
Read key bindings from filename.
- -q function
-
Query about which keys invoke the named function.
- -u function
-
Unbind all keys bound to the named function.
- -r keyseq
-
Remove any current binding for keyseq.
- -x keyseq:shell-command
-
Cause shell-command to be executed whenever keyseq is
entered.
When shell-command is executed, the shell sets the
READLINE_LINE
variable to the contents of the readline line buffer and the
READLINE_POINT
variable to the current location of the insertion point.
If the executed command changes the value of
READLINE_LINE
or
READLINE_POINT,
those new values will be reflected in the editing state.
- -X
-
List all key sequences bound to shell commands and the associated commands
in a format that can be reused as input.
The return value is 0 unless an unrecognized option is given or an
error occurred.
- break [n]
-
Exit from within a
for,
while,
until,
or
select
loop. If n is specified, break n levels.
n
must be >= 1. If
n
is greater than the number of enclosing loops, all enclosing loops
are exited.
The return value is 0 unless n is not greater than or equal to 1.
- builtin shell-builtin [arguments]
-
Execute the specified shell builtin, passing it
arguments,
and return its exit status.
This is useful when defining a
function whose name is the same as a shell builtin,
retaining the functionality of the builtin within the function.
The cd builtin is commonly redefined this way.
The return status is false if
shell-builtin
is not a shell builtin command.
- caller [expr]
-
Returns the context of any active subroutine call (a shell function or
a script executed with the . or source builtins).
Without expr, caller displays the line number and source
filename of the current subroutine call.
If a non-negative integer is supplied as expr, caller
displays the line number, subroutine name, and source file corresponding
to that position in the current execution call stack. This extra
information may be used, for example, to print a stack trace. The
current frame is frame 0.
The return value is 0 unless the shell is not executing a subroutine
call or expr does not correspond to a valid position in the
call stack.
- cd [-L|[-P [-e]] [-@]] [dir]
-
Change the current directory to dir.
if dir is not supplied, the value of the
HOME
shell variable is the default.
Any additional arguments following dir are ignored.
The variable
CDPATH
defines the search path for the directory containing
dir:
each directory name in
CDPATH
is searched for dir.
Alternative directory names in
CDPATH
are separated by a colon (:). A null directory name in
CDPATH
is the same as the current directory, i.e., ``.''. If
dir
begins with a slash (/),
then
CDPATH
is not used. The
-P
option causes cd to use the physical directory structure
by resolving symbolic links while traversing dir and
before processing instances of .. in dir (see also the
-P
option to the
set
builtin command); the
-L
option forces symbolic links to be followed by resolving the link
after processing instances of .. in dir.
If .. appears in dir, it is processed by removing the
immediately previous pathname component from dir, back to a slash
or the beginning of dir.
If the
-e
option is supplied with
-P,
and the current working directory cannot be successfully determined
after a successful directory change, cd will return an unsuccessful
status.
On systems that support it, the -@ option presents the extended
attributes associated with a file as a directory.
An argument of
-
is converted to
$OLDPWD
before the directory change is attempted.
If a non-empty directory name from
CDPATH
is used, or if
- is the first argument, and the directory change is
successful, the absolute pathname of the new working directory is
written to the standard output.
The return value is true if the directory was successfully changed;
false otherwise.
- command [-pVv] command [arg ...]
-
Run
command
with
args
suppressing the normal shell function lookup. Only builtin
commands or commands found in the
PATH
are executed. If the
-p
option is given, the search for
command
is performed using a default value for
PATH
that is guaranteed to find all of the standard utilities.
If either the
-V
or
-v
option is supplied, a description of
command
is printed. The
-v
option causes a single word indicating the command or filename
used to invoke
command
to be displayed; the
-V
option produces a more verbose description.
If the
-V
or
-v
option is supplied, the exit status is 0 if
command
was found, and 1 if not. If neither option is supplied and
an error occurred or
command
cannot be found, the exit status is 127. Otherwise, the exit status of the
command
builtin is the exit status of
command.
- compgen [option] [word]
-
Generate possible completion matches for word according to
the options, which may be any option accepted by the
complete
builtin with the exception of -p and -r, and write
the matches to the standard output.
When using the -F or -C options, the various shell variables
set by the programmable completion facilities, while available, will not
have useful values.
The matches will be generated in the same way as if the programmable
completion code had generated them directly from a completion specification
with the same flags.
If word is specified, only those completions matching word
will be displayed.
The return value is true unless an invalid option is supplied, or no
matches were generated.
- complete [-abcdefgjksuv] [-o comp-option] [-DE] [-A action] [-G globpat] [-W wordlist] [-F function] [-C command]
-
[-X filterpat] [-P prefix] [-S suffix] name [name ...]
- complete -pr [-DE] [name ...]
-
Specify how arguments to each name should be completed.
If the -p option is supplied, or if no options are supplied,
existing completion specifications are printed in a way that allows
them to be reused as input.
The -r option removes a completion specification for
each name, or, if no names are supplied, all
completion specifications.
The -D option indicates that the remaining options and actions should
apply to the ``default'' command completion; that is, completion attempted
on a command for which no completion has previously been defined.
The -E option indicates that the remaining options and actions should
apply to ``empty'' command completion; that is, completion attempted on a
blank line.
The process of applying these completion specifications when word completion
is attempted is described above under Programmable Completion.
Other options, if specified, have the following meanings.
The arguments to the -G, -W, and -X options
(and, if necessary, the -P and -S options)
should be quoted to protect them from expansion before the
complete
builtin is invoked.
-
- -o comp-option
-
The comp-option controls several aspects of the compspec's behavior
beyond the simple generation of completions.
comp-option may be one of:
-
- bashdefault
-
Perform the rest of the default bash completions if the compspec
generates no matches.
- default
-
Use readline's default filename completion if the compspec generates
no matches.
- dirnames
-
Perform directory name completion if the compspec generates no matches.
- filenames
-
Tell readline that the compspec generates filenames, so it can perform any
filename-specific processing (like adding a slash to directory names,
quoting special characters, or suppressing trailing spaces).
Intended to be used with shell functions.
- noquote
-
Tell readline not to quote the completed words if they are filenames
(quoting filenames is the default).
- nospace
-
Tell readline not to append a space (the default) to words completed at
the end of the line.
- plusdirs
-
After any matches defined by the compspec are generated,
directory name completion is attempted and any
matches are added to the results of the other actions.
- -A action
-
The action may be one of the following to generate a list of possible
completions:
-
- alias
-
Alias names. May also be specified as -a.
- arrayvar
-
Array variable names.
- binding
-
Readline key binding names.
- builtin
-
Names of shell builtin commands. May also be specified as -b.
- command
-
Command names. May also be specified as -c.
- directory
-
Directory names. May also be specified as -d.
- disabled
-
Names of disabled shell builtins.
- enabled
-
Names of enabled shell builtins.
- export
-
Names of exported shell variables. May also be specified as -e.
- file
-
File names. May also be specified as -f.
- function
-
Names of shell functions.
- group
-
Group names. May also be specified as -g.
- helptopic
-
Help topics as accepted by the help builtin.
- hostname
-
Hostnames, as taken from the file specified by the
HOSTFILE
shell variable.
- job
-
Job names, if job control is active. May also be specified as -j.
- keyword
-
Shell reserved words. May also be specified as -k.
- running
-
Names of running jobs, if job control is active.
- service
-
Service names. May also be specified as -s.
- setopt
-
Valid arguments for the -o option to the set builtin.
- shopt
-
Shell option names as accepted by the shopt builtin.
- signal
-
Signal names.
- stopped
-
Names of stopped jobs, if job control is active.
- user
-
User names. May also be specified as -u.
- variable
-
Names of all shell variables. May also be specified as -v.
- -C command
-
command is executed in a subshell environment, and its output is
used as the possible completions.
- -F function
-
The shell function function is executed in the current shell
environment.
When the function is executed,
the first argument ($1) is the name of the command whose arguments are
being completed,
the second argument ($2) is the word being completed,
and the third argument ($3) is the word preceding the word being
completed on the current command line.
When it finishes, the possible completions are retrieved from the value
of the
COMPREPLY
array variable.
- -G globpat
-
The pathname expansion pattern globpat is expanded to generate
the possible completions.
- -P prefix
-
prefix is added at the beginning of each possible completion
after all other options have been applied.
- -S suffix
-
suffix is appended to each possible completion
after all other options have been applied.
- -W wordlist
-
The wordlist is split using the characters in the
IFS
special variable as delimiters, and each resultant word is expanded.
The possible completions are the members of the resultant list which
match the word being completed.
- -X filterpat
-
filterpat is a pattern as used for pathname expansion.
It is applied to the list of possible completions generated by the
preceding options and arguments, and each completion matching
filterpat is removed from the list.
A leading ! in filterpat negates the pattern; in this
case, any completion not matching filterpat is removed.
The return value is true unless an invalid option is supplied, an option
other than -p or -r is supplied without a name
argument, an attempt is made to remove a completion specification for
a name for which no specification exists, or
an error occurs adding a completion specification.
- compopt [-o option] [-DE] [+o option] [name]
-
Modify completion options for each name according to the
options, or for the
currently-executing completion if no names are supplied.
If no options are given, display the completion options for each
name or the current completion.
The possible values of option are those valid for the complete
builtin described above.
The -D option indicates that the remaining options should
apply to the ``default'' command completion; that is, completion attempted
on a command for which no completion has previously been defined.
The -E option indicates that the remaining options should
apply to ``empty'' command completion; that is, completion attempted on a
blank line.
The return value is true unless an invalid option is supplied, an attempt
is made to modify the options for a name for which no completion
specification exists, or an output error occurs.
- continue [n]
-
Resume the next iteration of the enclosing
for,
while,
until,
or
select
loop.
If
n
is specified, resume at the nth enclosing loop.
n
must be >= 1. If
n
is greater than the number of enclosing loops, the last enclosing loop
(the ``top-level'' loop) is resumed.
The return value is 0 unless n is not greater than or equal to 1.
- declare [-aAfFgilnrtux] [-p] [name[=value] ...]
-
- typeset [-aAfFgilnrtux] [-p] [name[=value] ...]
-
Declare variables and/or give them attributes.
If no names are given then display the values of variables.
The
-p
option will display the attributes and values of each
name.
When
-p
is used with name arguments, additional options,
other than -f and -F, are ignored.
When
-p
is supplied without name arguments, it will display the attributes
and values of all variables having the attributes specified by the
additional options.
If no other options are supplied with -p, declare will display
the attributes and values of all shell variables. The -f option
will restrict the display to shell functions.
The
-F
option inhibits the display of function definitions; only the
function name and attributes are printed.
If the extdebug shell option is enabled using shopt,
the source file name and line number where the function is defined
are displayed as well. The
-F
option implies
-f.
The
-g
option forces variables to be created or modified at the global scope,
even when declare is executed in a shell function.
It is ignored in all other cases.
The following options can
be used to restrict output to variables with the specified attribute or
to give variables attributes:
-
- -a
-
Each name is an indexed array variable (see
Arrays
above).
- -A
-
Each name is an associative array variable (see
Arrays
above).
- -f
-
Use function names only.
- -i
-
The variable is treated as an integer; arithmetic evaluation (see
ARITHMETIC EVALUATION
above) is performed when the variable is assigned a value.
- -l
-
When the variable is assigned a value, all upper-case characters are
converted to lower-case.
The upper-case attribute is disabled.
- -n
-
Give each name the nameref attribute, making
it a name reference to another variable.
That other variable is defined by the value of name.
All references and assignments to name, except for changing the
-n attribute itself, are performed on the variable referenced by
name's value.
The -n attribute cannot be applied to array variables.
- -r
-
Make names readonly. These names cannot then be assigned values
by subsequent assignment statements or unset.
- -t
-
Give each name the trace attribute.
Traced functions inherit the DEBUG and RETURN traps from
the calling shell.
The trace attribute has no special meaning for variables.
- -u
-
When the variable is assigned a value, all lower-case characters are
converted to upper-case.
The lower-case attribute is disabled.
- -x
-
Mark names for export to subsequent commands via the environment.
Using `+' instead of `-'
turns off the attribute instead,
with the exceptions that +a
may not be used to destroy an array variable and +r will not
remove the readonly attribute.
When used in a function,
declare
and
typeset
make each
name local, as with the
local
command,
unless the -g option is supplied.
If a variable name is followed by =value, the value of
the variable is set to value.
When using -a or -A and the compound assignment syntax to
create array variables, additional attributes do not take effect until
subsequent assignments.
The return value is 0 unless an invalid option is encountered,
an attempt is made to define a function using
-f foo=bar,
an attempt is made to assign a value to a readonly variable,
an attempt is made to assign a value to an array variable without
using the compound assignment syntax (see
Arrays
above), one of the names is not a valid shell variable name,
an attempt is made to turn off readonly status for a readonly variable,
an attempt is made to turn off array status for an array variable,
or an attempt is made to display a non-existent function with -f.
- dirs [-clpv] [+n] [-n]
-
Without options, displays the list of currently remembered directories.
The default display is on a single line with directory names separated
by spaces.
Directories are added to the list with the
pushd
command; the
popd
command removes entries from the list.
-
- -c
-
Clears the directory stack by deleting all of the entries.
- -l
-
Produces a listing using full pathnames;
the default listing format uses a tilde to denote the home directory.
- -p
-
Print the directory stack with one entry per line.
- -v
-
Print the directory stack with one entry per line,
prefixing each entry with its index in the stack.
- +n
-
Displays the nth entry counting from the left of the list
shown by
dirs
when invoked without options, starting with zero.
- -n
-
Displays the nth entry counting from the right of the list
shown by
dirs
when invoked without options, starting with zero.
The return value is 0 unless an
invalid option is supplied or n indexes beyond the end
of the directory stack.
- disown [-ar] [-h] [jobspec ...]
-
Without options, remove each
jobspec
from the table of active jobs.
If
jobspec
is not present, and neither the -a nor the -r option
is supplied, the current job is used.
If the -h option is given, each
jobspec
is not removed from the table, but is marked so that
SIGHUP
is not sent to the job if the shell receives a
SIGHUP.
If no
jobspec
is supplied, the
-a
option means to remove or mark all jobs; the
-r
option without a
jobspec
argument restricts operation to running jobs.
The return value is 0 unless a
jobspec
does not specify a valid job.
- echo [-neE] [arg ...]
-
Output the args, separated by spaces, followed by a newline.
The return status is 0 unless a write error occurs.
If -n is specified, the trailing newline is
suppressed. If the -e option is given, interpretation of
the following backslash-escaped characters is enabled. The
-E
option disables the interpretation of these escape characters,
even on systems where they are interpreted by default.
The xpg_echo shell option may be used to
dynamically determine whether or not echo expands these
escape characters by default.
echo
does not interpret -- to mean the end of options.
echo
interprets the following escape sequences:
-
- \a
-
alert (bell)
- \b
-
backspace
- \c
-
suppress further output
- \e
-
- \E
-
an escape character
- \f
-
form feed
- \n
-
new line
- \r
-
carriage return
- \t
-
horizontal tab
- \v
-
vertical tab
- \\
-
backslash
- \0nnn
-
the eight-bit character whose value is the octal value nnn
(zero to three octal digits)
- \xHH
-
the eight-bit character whose value is the hexadecimal value HH
(one or two hex digits)
- \uHHHH
-
the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
HHHH (one to four hex digits)
- \UHHHHHHHH
-
the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
HHHHHHHH (one to eight hex digits)
- enable [-a] [-dnps] [-f filename] [name ...]
-
Enable and disable builtin shell commands.
Disabling a builtin allows a disk command which has the same name
as a shell builtin to be executed without specifying a full pathname,
even though the shell normally searches for builtins before disk commands.
If -n is used, each name
is disabled; otherwise,
names are enabled. For example, to use the
test
binary found via the
PATH
instead of the shell builtin version, run
enable -n test.
The
-f
option means to load the new builtin command
name
from shared object
filename,
on systems that support dynamic loading. The
-d
option will delete a builtin previously loaded with
-f.
If no name arguments are given, or if the
-p
option is supplied, a list of shell builtins is printed.
With no other option arguments, the list consists of all enabled
shell builtins.
If -n is supplied, only disabled builtins are printed.
If -a is supplied, the list printed includes all builtins, with an
indication of whether or not each is enabled.
If -s is supplied, the output is restricted to the POSIX
special builtins.
The return value is 0 unless a
name
is not a shell builtin or there is an error loading a new builtin
from a shared object.
- eval [arg ...]
-
The args are read and concatenated together into a single
command. This command is then read and executed by the shell, and
its exit status is returned as the value of
eval.
If there are no
args,
or only null arguments,
eval
returns 0.
- exec [-cl] [-a name] [command [arguments]]
-
If
command
is specified, it replaces the shell.
No new process is created. The
arguments
become the arguments to command.
If the
-l
option is supplied,
the shell places a dash at the beginning of the zeroth argument passed to
command.
This is what
login(1)
does. The
-c
option causes
command
to be executed with an empty environment. If
-a
is supplied, the shell passes
name
as the zeroth argument to the executed command.
If
command
cannot be executed for some reason, a non-interactive shell exits,
unless the
execfail
shell option
is enabled. In that case, it returns failure.
An interactive shell returns failure if the file cannot be executed.
If
command
is not specified, any redirections take effect in the current shell,
and the return status is 0. If there is a redirection error, the
return status is 1.
- exit [n]
-
Cause the shell to exit
with a status of n. If
n
is omitted, the exit status
is that of the last command executed.
A trap on
EXIT
is executed before the shell terminates.
- export [-fn] [name[=word]] ...
-
- export -p
-
The supplied
names
are marked for automatic export to the environment of
subsequently executed commands. If the
-f
option is given,
the
names
refer to functions.
If no
names
are given, or if the
-p
option is supplied, a list
of names of all exported variables is printed.
The
-n
option causes the export property to be removed from each
name.
If a variable name is followed by =word, the value of
the variable is set to word.
export
returns an exit status of 0 unless an invalid option is
encountered,
one of the names is not a valid shell variable name, or
-f
is supplied with a
name
that is not a function.
- fc [-e ename] [-lnr] [first] [last]
-
- fc -s [pat=rep] [cmd]
-
The first form selects a range of commands from
first
to
last
from the history list and displays or edits and re-executes them.
First
and
last
may be specified as a string (to locate the last command beginning
with that string) or as a number (an index into the history list,
where a negative number is used as an offset from the current
command number). If
last
is not specified it is set to
the current command for listing (so that
fc -l -10
prints the last 10 commands) and to
first
otherwise.
If
first
is not specified it is set to the previous
command for editing and -16 for listing.
The
-n
option suppresses
the command numbers when listing. The
-r
option reverses the order of
the commands. If the
-l
option is given,
the commands are listed on
standard output. Otherwise, the editor given by
ename
is invoked
on a file containing those commands. If
ename
is not given, the
value of the
FCEDIT
variable is used, and
the value of
EDITOR
if
FCEDIT
is not set. If neither variable is set,
vi
is used. When editing is complete, the edited commands are
echoed and executed.
In the second form, command is re-executed after each instance
of pat is replaced by rep.
Command is intepreted the same as first above.
A useful alias to use with this is
r='fc -s',
so that typing
r cc
runs the last command beginning with
cc
and typing
r
re-executes the last command.
If the first form is used, the return value is 0 unless an invalid
option is encountered or
first
or
last
specify history lines out of range.
If the
-e
option is supplied, the return value is the value of the last
command executed or failure if an error occurs with the temporary
file of commands. If the second form is used, the return status
is that of the command re-executed, unless
cmd
does not specify a valid history line, in which case
fc
returns failure.
- fg [jobspec]
-
Resume
jobspec
in the foreground, and make it the current job.
If
jobspec
is not present, the shell's notion of the current job is used.
The return value is that of the command placed into the foreground,
or failure if run when job control is disabled or, when run with
job control enabled, if
jobspec
does not specify a valid job or
jobspec
specifies a job that was started without job control.
- getopts optstring name [args]
-
getopts
is used by shell procedures to parse positional parameters.
optstring
contains the option characters to be recognized; if a character
is followed by a colon, the option is expected to have an
argument, which should be separated from it by white space.
The colon and question mark characters may not be used as
option characters.
Each time it is invoked,
getopts
places the next option in the shell variable
name,
initializing
name
if it does not exist,
and the index of the next argument to be processed into the
variable
OPTIND.
OPTIND
is initialized to 1 each time the shell or a shell script
is invoked. When an option requires an argument,
getopts
places that argument into the variable
OPTARG.
The shell does not reset
OPTIND
automatically; it must be manually reset between multiple
calls to
getopts
within the same shell invocation if a new set of parameters
is to be used.
When the end of options is encountered, getopts exits with a
return value greater than zero.
OPTIND
is set to the index of the first non-option argument,
and name is set to ?.
getopts
normally parses the positional parameters, but if more arguments are
given in
args,
getopts
parses those instead.
getopts
can report errors in two ways. If the first character of
optstring
is a colon,
silent
error reporting is used. In normal operation, diagnostic messages
are printed when invalid options or missing option arguments are
encountered.
If the variable
OPTERR
is set to 0, no error messages will be displayed, even if the first
character of
optstring
is not a colon.
If an invalid option is seen,
getopts
places ? into
name
and, if not silent,
prints an error message and unsets
OPTARG.
If
getopts
is silent,
the option character found is placed in
OPTARG
and no diagnostic message is printed.
If a required argument is not found, and
getopts
is not silent,
a question mark (?) is placed in
name,
OPTARG
is unset, and a diagnostic message is printed.
If
getopts
is silent, then a colon (:) is placed in
name
and
OPTARG
is set to the option character found.
getopts
returns true if an option, specified or unspecified, is found.
It returns false if the end of options is encountered or an
error occurs.
- hash [-lr] [-p filename] [-dt] [name]
-
Each time hash is invoked,
the full pathname of the command
name
is determined by searching
the directories in
$PATH
and remembered. Any previously-remembered pathname is discarded.
If the
-p
option is supplied, no path search is performed, and
filename
is used as the full filename of the command.
The
-r
option causes the shell to forget all
remembered locations.
The
-d
option causes the shell to forget the remembered location of each name.
If the
-t
option is supplied, the full pathname to which each name corresponds
is printed. If multiple name arguments are supplied with -t,
the name is printed before the hashed full pathname.
The
-l
option causes output to be displayed in a format that may be reused as input.
If no arguments are given, or if only -l is supplied,
information about remembered commands is printed.
The return status is true unless a
name
is not found or an invalid option is supplied.
- help [-dms] [pattern]
-
Display helpful information about builtin commands. If
pattern
is specified,
help
gives detailed help on all commands matching
pattern;
otherwise help for all the builtins and shell control structures
is printed.
-
- -d
-
Display a short description of each pattern
- -m
-
Display the description of each pattern in a manpage-like format
- -s
-
Display only a short usage synopsis for each pattern
The return status is 0 unless no command matches
pattern.
- history [n]
-
- history -c
-
- history -d offset
-
- history -anrw [filename]
-
- history -p arg [arg ...]
-
- history -s arg [arg ...]
-
With no options, display the command
history list with line numbers. Lines listed
with a
*
have been modified. An argument of
n
lists only the last
n
lines.
If the shell variable
HISTTIMEFORMAT
is set and not null,
it is used as a format string for strftime(3) to display
the time stamp associated with each displayed history entry.
No intervening blank is printed between the formatted time stamp
and the history line.
If filename is supplied, it is used as the
name of the history file; if not, the value of
HISTFILE
is used. Options, if supplied, have the following meanings:
-
- -c
-
Clear the history list by deleting all the entries.
- -d offset
-
Delete the history entry at position offset.
- -a
-
Append the ``new'' history lines (history lines entered since the
beginning of the current bash session) to the history file.
- -n
-
Read the history lines not already read from the history
file into the current history list. These are lines
appended to the history file since the beginning of the
current bash session.
- -r
-
Read the contents of the history file
and append them to the current history list.
- -w
-
Write the current history list to the history file, overwriting the
history file's contents.
- -p
-
Perform history substitution on the following args and display
the result on the standard output.
Does not store the results in the history list.
Each arg must be quoted to disable normal history expansion.
- -s
-
Store the
args
in the history list as a single entry. The last command in the
history list is removed before the
args
are added.
If the
HISTTIMEFORMAT
variable is set, the time stamp information
associated with each history entry is written to the history file,
marked with the history comment character.
When the history file is read, lines beginning with the history
comment character followed immediately by a digit are interpreted
as timestamps for the previous history line.
The return value is 0 unless an invalid option is encountered, an
error occurs while reading or writing the history file, an invalid
offset is supplied as an argument to -d, or the
history expansion supplied as an argument to -p fails.
- jobs [-lnprs] [ jobspec ... ]
-
- jobs -x command [ args ... ]
-
The first form lists the active jobs. The options have the following
meanings:
-
- -l
-
List process IDs
in addition to the normal information.
- -n
-
Display information only about jobs that have changed status since
the user was last notified of their status.
- -p
-
List only the process ID of the job's process group
leader.
- -r
-
Display only running jobs.
- -s
-
Display only stopped jobs.
If
jobspec
is given, output is restricted to information about that job.
The return status is 0 unless an invalid option is encountered
or an invalid
jobspec
is supplied.
If the
-x
option is supplied,
jobs
replaces any
jobspec
found in
command
or
args
with the corresponding process group ID, and executes
command
passing it
args,
returning its exit status.
- kill [-s sigspec | -n signum | -sigspec] [pid | jobspec] ...
-
- kill -l [sigspec | exit_status]
-
Send the signal named by
sigspec
or
signum
to the processes named by
pid
or
jobspec.
sigspec
is either a case-insensitive signal name such as
SIGKILL
(with or without the
SIG
prefix) or a signal number;
signum
is a signal number.
If
sigspec
is not present, then
SIGTERM
is assumed.
An argument of
-l
lists the signal names.
If any arguments are supplied when
-l
is given, the names of the signals corresponding to the arguments are
listed, and the return status is 0.
The exit_status argument to
-l
is a number specifying either a signal number or the exit status of
a process terminated by a signal.
kill
returns true if at least one signal was successfully sent, or false
if an error occurs or an invalid option is encountered.
- let arg [arg ...]
-
Each
arg
is an arithmetic expression to be evaluated (see
ARITHMETIC EVALUATION
above).
If the last
arg
evaluates to 0,
let
returns 1; 0 is returned otherwise.
- local [option] [name[=value] ...]
-
For each argument, a local variable named
name
is created, and assigned
value.
The option can be any of the options accepted by declare.
When
local
is used within a function, it causes the variable
name
to have a visible scope restricted to that function and its children.
With no operands,
local
writes a list of local variables to the standard output. It is
an error to use
local
when not within a function. The return status is 0 unless
local
is used outside a function, an invalid
name
is supplied, or
name is a readonly variable.
- logout
-
Exit a login shell.
- mapfile [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback] [-c quantum] [array]
-
- readarray [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback] [-c quantum] [array]
-
Read lines from the standard input into the indexed array variable
array,
or from file descriptor
fd
if the
-u
option is supplied.
The variable
MAPFILE
is the default array.
Options, if supplied, have the following meanings:
-
- -n
-
Copy at most
count
lines. If count is 0, all lines are copied.
- -O
-
Begin assigning to
array
at index
origin.
The default index is 0.
- -s
-
Discard the first count lines read.
- -t
-
Remove a trailing newline from each line read.
- -u
-
Read lines from file descriptor fd instead of the standard input.
- -C
-
Evaluate
callback
each time quantum lines are read. The -c option specifies
quantum.
- -c
-
Specify the number of lines read between each call to
callback.
If
-C
is specified without
-c,
the default quantum is 5000.
When callback is evaluated, it is supplied the index of the next
array element to be assigned and the line to be assigned to that element
as additional arguments.
callback is evaluated after the line is read but before the
array element is assigned.
If not supplied with an explicit origin, mapfile will clear array
before assigning to it.
mapfile returns successfully unless an invalid option or option
argument is supplied, array is invalid or unassignable, or if
array is not an indexed array.
- popd [-n] [+n] [-n]
-
Removes entries from the directory stack. With no arguments,
removes the top directory from the stack, and performs a
cd
to the new top directory.
Arguments, if supplied, have the following meanings:
-
- -n
-
Suppresses the normal change of directory when removing directories
from the stack, so that only the stack is manipulated.
- +n
-
Removes the nth entry counting from the left of the list
shown by
dirs,
starting with zero. For example:
popd +0
removes the first directory,
popd +1
the second.
- -n
-
Removes the nth entry counting from the right of the list
shown by
dirs,
starting with zero. For example:
popd -0
removes the last directory,
popd -1
the next to last.
If the
popd
command is successful, a
dirs
is performed as well, and the return status is 0.
popd
returns false if an invalid option is encountered, the directory stack
is empty, a non-existent directory stack entry is specified, or the
directory change fails.
- printf [-v var] format [arguments]
-
Write the formatted arguments to the standard output under the
control of the format.
The -v option causes the output to be assigned to the variable
var rather than being printed to the standard output.
The format is a character string which contains three types of objects:
plain characters, which are simply copied to standard output, character
escape sequences, which are converted and copied to the standard output, and
format specifications, each of which causes printing of the next successive
argument.
In addition to the standard printf(1) format specifications,
printf interprets the following extensions:
-
- %b
-
causes
printf to expand backslash escape sequences in the corresponding
argument (except that \c terminates output, backslashes in
\aq, \", and \? are not removed, and octal escapes
beginning with \0 may contain up to four digits).
- %q
-
causes printf to output the corresponding
argument in a format that can be reused as shell input.
- %(datefmt)T
-
causes printf to output the date-time string resulting from using
datefmt as a format string for strftime(3).
The corresponding argument is an integer representing the number of
seconds since the epoch.
Two special argument values may be used: -1 represents the current
time, and -2 represents the time the shell was invoked.
If no argument is specified, conversion behaves as if -1 had been given.
This is an exception to the usual printf behavior.
Arguments to non-string format specifiers are treated as C constants,
except that a leading plus or minus sign is allowed, and if the leading
character is a single or double quote, the value is the ASCII value of
the following character.
The format is reused as necessary to consume all of the arguments.
If the format requires more arguments than are supplied, the
extra format specifications behave as if a zero value or null string, as
appropriate, had been supplied.
The return value is zero on success, non-zero on failure.
- pushd [-n] [+n] [-n]
-
- pushd [-n] [dir]
-
Adds a directory to the top of the directory stack, or rotates
the stack, making the new top of the stack the current working
directory. With no arguments, exchanges the top two directories
and returns 0, unless the directory stack is empty.
Arguments, if supplied, have the following meanings:
-
- -n
-
Suppresses the normal change of directory when adding directories
to the stack, so that only the stack is manipulated.
- +n
-
Rotates the stack so that the nth directory
(counting from the left of the list shown by
dirs,
starting with zero)
is at the top.
- -n
-
Rotates the stack so that the nth directory
(counting from the right of the list shown by
dirs,
starting with zero) is at the top.
- dir
-
Adds
dir
to the directory stack at the top, making it the
new current working directory as if it had been supplied as the argument
to the cd builtin.
If the
pushd
command is successful, a
dirs
is performed as well.
If the first form is used,
pushd
returns 0 unless the cd to
dir
fails. With the second form,
pushd
returns 0 unless the directory stack is empty,
a non-existent directory stack element is specified,
or the directory change to the specified new current directory
fails.
- pwd [-LP]
-
Print the absolute pathname of the current working directory.
The pathname printed contains no symbolic links if the
-P
option is supplied or the
-o physical
option to the
set
builtin command is enabled.
If the
-L
option is used, the pathname printed may contain symbolic links.
The return status is 0 unless an error occurs while
reading the name of the current directory or an
invalid option is supplied.
- read [-ers] [-a aname] [-d delim] [-i text] [-n nchars] [-N nchars] [-p prompt] [-t timeout] [-u fd] [name ...]
-
One line is read from the standard input, or from the file descriptor
fd supplied as an argument to the -u option, and the first word
is assigned to the first
name,
the second word to the second
name,
and so on, with leftover words and their intervening separators assigned
to the last
name.
If there are fewer words read from the input stream than names,
the remaining names are assigned empty values.
The characters in
IFS
are used to split the line into words using the same rules the shell
uses for expansion (described above under Word Splitting).
The backslash character (\) may be used to remove any special
meaning for the next character read and for line continuation.
Options, if supplied, have the following meanings:
-
- -a aname
-
The words are assigned to sequential indices
of the array variable
aname,
starting at 0.
aname
is unset before any new values are assigned.
Other name arguments are ignored.
- -d delim
-
The first character of delim is used to terminate the input line,
rather than newline.
- -e
-
If the standard input
is coming from a terminal,
readline
(see
READLINE
above) is used to obtain the line.
Readline uses the current (or default, if line editing was not previously
active) editing settings.
- -i text
-
If
readline
is being used to read the line, text is placed into the editing
buffer before editing begins.
- -n nchars
-
read returns after reading nchars characters rather than
waiting for a complete line of input, but honor a delimiter if fewer
than nchars characters are read before the delimiter.
- -N nchars
-
read returns after reading exactly nchars characters rather
than waiting for a complete line of input, unless EOF is encountered or
read times out.
Delimiter characters encountered in the input are
not treated specially and do not cause read to return until
nchars characters are read.
- -p prompt
-
Display prompt on standard error, without a
trailing newline, before attempting to read any input. The prompt
is displayed only if input is coming from a terminal.
- -r
-
Backslash does not act as an escape character.
The backslash is considered to be part of the line.
In particular, a backslash-newline pair may not be used as a line
continuation.
- -s
-
Silent mode. If input is coming from a terminal, characters are
not echoed.
- -t timeout
-
Cause read to time out and return failure if a complete line of
input (or a specified number of characters)
is not read within timeout seconds.
timeout may be a decimal number with a fractional portion following
the decimal point.
This option is only effective if read is reading input from a
terminal, pipe, or other special file; it has no effect when reading
from regular files.
If read times out, read saves any partial input read into
the specified variable name.
If timeout is 0, read returns immediately, without trying to
read any data. The exit status is 0 if input is available on
the specified file descriptor, non-zero otherwise.
The exit status is greater than 128 if the timeout is exceeded.
- -u fd
-
Read input from file descriptor fd.
If no
names
are supplied, the line read is assigned to the variable
REPLY.
The return code is zero, unless end-of-file is encountered, read
times out (in which case the return code is greater than 128),
a variable assignment error (such as assigning to a readonly variable) occurs,
or an invalid file descriptor is supplied as the argument to -u.
- readonly [-aAf] [-p] [name[=word] ...]
-
The given
names are marked readonly; the values of these
names
may not be changed by subsequent assignment.
If the
-f
option is supplied, the functions corresponding to the
names are so
marked.
The
-a
option restricts the variables to indexed arrays; the
-A
option restricts the variables to associative arrays.
If both options are supplied,
-A
takes precedence.
If no
name
arguments are given, or if the
-p
option is supplied, a list of all readonly names is printed.
The other options may be used to restrict the output to a subset of
the set of readonly names.
The
-p
option causes output to be displayed in a format that
may be reused as input.
If a variable name is followed by =word, the value of
the variable is set to word.
The return status is 0 unless an invalid option is encountered,
one of the
names
is not a valid shell variable name, or
-f
is supplied with a
name
that is not a function.
- return [n]
-
Causes a function to stop executing and return the value specified by
n
to its caller.
If
n
is omitted, the return status is that of the last command
executed in the function body. If
return
is used outside a function,
but during execution of a script by the
.
(source) command, it causes the shell to stop executing
that script and return either
n
or the exit status of the last command executed within the
script as the exit status of the script.
If n is supplied, the return value is its least significant
8 bits.
The return status is non-zero if
return
is supplied a non-numeric argument, or
is used outside a
function and not during execution of a script by . or source.
Any command associated with the RETURN trap is executed
before execution resumes after the function or script.
- set [--abefhkmnptuvxBCEHPT] [-o option-name] [arg ...]
-
- set [+abefhkmnptuvxBCEHPT] [+o option-name] [arg ...]
-
Without options, the name and value of each shell variable are displayed
in a format that can be reused as input
for setting or resetting the currently-set variables.
Read-only variables cannot be reset.
In posix mode, only shell variables are listed.
The output is sorted according to the current locale.
When options are specified, they set or unset shell attributes.
Any arguments remaining after option processing are treated
as values for the positional parameters and are assigned, in order, to
$1,
$2,
...
$n.
Options, if specified, have the following meanings:
-
- -a
-
Automatically mark variables and functions which are modified or
created for export to the environment of subsequent commands.
- -b
-
Report the status of terminated background jobs
immediately, rather than before the next primary prompt. This is
effective only when job control is enabled.
- -e
-
Exit immediately if a
pipeline (which may consist of a single simple command),
a list,
or a compound command
(see
SHELL GRAMMAR
above), exits with a non-zero status.
The shell does not exit if the
command that fails is part of the command list immediately following a
while
or
until
keyword,
part of the test following the
if
or
elif
reserved words, part of any command executed in a
&&
or
||
list except the command following the final && or ||,
any command in a pipeline but the last,
or if the command's return value is
being inverted with
!.
If a compound command other than a subshell
returns a non-zero status because a command failed
while -e was being ignored, the shell does not exit.
A trap on ERR, if set, is executed before the shell exits.
This option applies to the shell environment and each subshell environment
separately (see
COMMAND EXECUTION ENVIRONMENT
above), and may cause
subshells to exit before executing all the commands in the subshell.
If a compound command or shell function executes in a context
where -e is being ignored,
none of the commands executed within the compound command or function body
will be affected by the -e setting, even if -e is set
and a command returns a failure status.
If a compound command or shell function sets -e while executing in
a context where -e is ignored, that setting will not have any
effect until the compound command or the command containing the function
call completes.
- -f
-
Disable pathname expansion.
- -h
-
Remember the location of commands as they are looked up for execution.
This is enabled by default.
- -k
-
All arguments in the form of assignment statements
are placed in the environment for a command, not just
those that precede the command name.
- -m
-
Monitor mode. Job control is enabled. This option is on
by default for interactive shells on systems that support
it (see
JOB CONTROL
above).
All processes run in a separate process group.
When a background job completes, the shell prints a line
containing its exit status.
- -n
-
Read commands but do not execute them. This may be used to
check a shell script for syntax errors. This is ignored by
interactive shells.
- -o option-name
-
The option-name can be one of the following:
-
- allexport
-
Same as
-a.
- braceexpand
-
Same as
-B.
- emacs
-
Use an emacs-style command line editing interface. This is enabled
by default when the shell is interactive, unless the shell is started
with the
--noediting
option.
This also affects the editing interface used for read -e.
- errexit
-
Same as
-e.
- errtrace
-
Same as
-E.
- functrace
-
Same as
-T.
- hashall
-
Same as
-h.
- histexpand
-
Same as
-H.
- history
-
Enable command history, as described above under
HISTORY.
This option is on by default in interactive shells.
- ignoreeof
-
The effect is as if the shell command
IGNOREEOF=10
had been executed
(see
Shell Variables
above).
- keyword
-
Same as
-k.
- monitor
-
Same as
-m.
- noclobber
-
Same as
-C.
- noexec
-
Same as
-n.
- noglob
-
Same as
-f.
- nolog
-
Currently ignored.
- notify
-
Same as
-b.
- nounset
-
Same as
-u.
- onecmd
-
Same as
-t.
- physical
-
Same as
-P.
- pipefail
-
If set, the return value of a pipeline is the value of the last
(rightmost) command to exit with a non-zero status, or zero if all
commands in the pipeline exit successfully.
This option is disabled by default.
- posix
-
Change the behavior of
bash
where the default operation differs
from the POSIX standard to match the standard (posix mode).
See
SEE ALSO
below for a reference to a document that details how posix mode affects
bash's behavior.
- privileged
-
Same as
-p.
- verbose
-
Same as
-v.
- vi
-
Use a vi-style command line editing interface.
This also affects the editing interface used for read -e.
- xtrace
-
Same as
-x.
If
-o
is supplied with no option-name, the values of the current options are
printed.
If
+o
is supplied with no option-name, a series of
set
commands to recreate the current option settings is displayed on
the standard output.
- -p
-
Turn on
privileged
mode. In this mode, the
$ENV
and
$BASH_ENV
files are not processed, shell functions are not inherited from the
environment, and the
SHELLOPTS,
BASHOPTS,
CDPATH,
and
GLOBIGNORE
variables, if they appear in the environment, are ignored.
If the shell is started with the effective user (group) id not equal to the
real user (group) id, and the -p option is not supplied, these actions
are taken and the effective user id is set to the real user id.
If the -p option is supplied at startup, the effective user id is
not reset.
Turning this option off causes the effective user
and group ids to be set to the real user and group ids.
- -t
-
Exit after reading and executing one command.
- -u
-
Treat unset variables and parameters other than the special
parameters "@" and "*" as an error when performing
parameter expansion. If expansion is attempted on an
unset variable or parameter, the shell prints an error message, and,
if not interactive, exits with a non-zero status.
- -v
-
Print shell input lines as they are read.
- -x
-
After expanding each simple command,
for command, case command, select command, or
arithmetic for command, display the expanded value of
PS4,
followed by the command and its expanded arguments
or associated word list.
- -B
-
The shell performs brace expansion (see
Brace Expansion
above). This is on by default.
- -C
-
If set,
bash
does not overwrite an existing file with the
>,
>&,
and
<>
redirection operators. This may be overridden when
creating output files by using the redirection operator
>|
instead of
>.
- -E
-
If set, any trap on ERR is inherited by shell functions, command
substitutions, and commands executed in a subshell environment.
The ERR trap is normally not inherited in such cases.
- -H
-
Enable
!
style history substitution. This option is on by
default when the shell is interactive.
- -P
-
If set, the shell does not resolve symbolic links when executing
commands such as
cd
that change the current working directory. It uses the
physical directory structure instead. By default,
bash
follows the logical chain of directories when performing commands
which change the current directory.
- -T
-
If set, any traps on DEBUG and RETURN are inherited by shell
functions, command substitutions, and commands executed in a
subshell environment.
The DEBUG and RETURN traps are normally not inherited
in such cases.
- --
-
If no arguments follow this option, then the positional parameters are
unset. Otherwise, the positional parameters are set to the
args, even if some of them begin with a
-.
- -
-
Signal the end of options, cause all remaining args to be
assigned to the positional parameters. The
-x
and
-v
options are turned off.
If there are no args,
the positional parameters remain unchanged.
The options are off by default unless otherwise noted.
Using + rather than - causes these options to be turned off.
The options can also be specified as arguments to an invocation of
the shell.
The current set of options may be found in
$-.
The return status is always true unless an invalid option is encountered.
- shift [n]
-
The positional parameters from n+1 ... are renamed to
$1
....
Parameters represented by the numbers $#
down to $#-n+1 are unset.
n
must be a non-negative number less than or equal to $#.
If
n
is 0, no parameters are changed.
If
n
is not given, it is assumed to be 1.
If
n
is greater than $#, the positional parameters are not changed.
The return status is greater than zero if
n
is greater than
$#
or less than zero; otherwise 0.
- shopt [-pqsu] [-o] [optname ...]
-
Toggle the values of settings controlling optional shell behavior.
The settings can be either those listed below, or, if the
-o
option is used, those available with the
-o
option to the set builtin command.
With no options, or with the
-p
option, a list of all settable options is displayed, with
an indication of whether or not each is set.
The -p option causes output to be displayed in a form that
may be reused as input.
Other options have the following meanings:
-
- -s
-
Enable (set) each optname.
- -u
-
Disable (unset) each optname.
- -q
-
Suppresses normal output (quiet mode); the return status indicates
whether the optname is set or unset.
If multiple optname arguments are given with
-q,
the return status is zero if all optnames are enabled; non-zero
otherwise.
- -o
-
Restricts the values of optname to be those defined for the
-o
option to the
set
builtin.
If either
-s
or
-u
is used with no optname arguments,
shopt
shows only those options which are set or unset, respectively.
Unless otherwise noted, the shopt options are disabled (unset)
by default.
The return status when listing options is zero if all optnames
are enabled, non-zero otherwise. When setting or unsetting options,
the return status is zero unless an optname is not a valid shell
option.
The list of shopt options is:
- autocd
-
If set, a command name that is the name of a directory is executed as if
it were the argument to the cd command.
This option is only used by interactive shells.
- cdable_vars
-
If set, an argument to the
cd
builtin command that
is not a directory is assumed to be the name of a variable whose
value is the directory to change to.
- cdspell
-
If set, minor errors in the spelling of a directory component in a
cd
command will be corrected.
The errors checked for are transposed characters,
a missing character, and one character too many.
If a correction is found, the corrected filename is printed,
and the command proceeds.
This option is only used by interactive shells.
- checkhash
-
If set, bash checks that a command found in the hash
table exists before trying to execute it. If a hashed command no
longer exists, a normal path search is performed.
- checkjobs
-
If set, bash lists the status of any stopped and running jobs before
exiting an interactive shell. If any jobs are running, this causes
the exit to be deferred until a second exit is attempted without an
intervening command (see
JOB CONTROL
above). The shell always
postpones exiting if any jobs are stopped.
- checkwinsize
-
If set, bash checks the window size after each command
and, if necessary, updates the values of
LINES
and
COLUMNS.
- cmdhist
-
If set,
bash
attempts to save all lines of a multiple-line
command in the same history entry. This allows
easy re-editing of multi-line commands.
- compat31
-
If set,
bash
changes its behavior to that of version 3.1 with respect to quoted
arguments to the [[ conditional command's =~ operator
and locale-specific string comparison when using the [[
conditional command's < and > operators.
Bash versions prior to bash-4.1 use ASCII collation and
strcmp(3);
bash-4.1 and later use the current locale's collation sequence and
strcoll(3).
- compat32
-
If set,
bash
changes its behavior to that of version 3.2 with respect to
locale-specific string comparison when using the [[
conditional command's < and > operators (see previous item).
- compat40
-
If set,
bash
changes its behavior to that of version 4.0 with respect to locale-specific
string comparison when using the [[
conditional command's < and > operators (see description of
compat31)
and the effect of interrupting a command list.
Bash versions 4.0 and later interrupt the list as if the shell received the
interrupt; previous versions continue with the next command in the list.
- compat41
-
If set,
bash,
when in posix mode, treats a single quote in a double-quoted
parameter expansion as a special character. The single quotes must match
(an even number) and the characters between the single quotes are considered
quoted. This is the behavior of posix mode through version 4.1.
The default bash behavior remains as in previous versions.
- compat42
-
If set,
bash
does not process the replacement string in the pattern substitution word
expansion using quote removal.
- complete_fullquote
-
If set,
bash
quotes all shell metacharacters in filenames and directory names when
performing completion.
If not set,
bash
removes metacharacters such as the dollar sign from the set of
characters that will be quoted in completed filenames
when these metacharacters appear in shell variable references in words to be
completed.
This means that dollar signs in variable names that expand to directories
will not be quoted;
however, any dollar signs appearing in filenames will not be quoted, either.
This is active only when bash is using backslashes to quote completed
filenames.
This variable is set by default, which is the default bash behavior in
versions through 4.2.
- direxpand
-
If set,
bash
replaces directory names with the results of word expansion when performing
filename completion. This changes the contents of the readline editing
buffer.
If not set,
bash
attempts to preserve what the user typed.
- dirspell
-
If set,
bash
attempts spelling correction on directory names during word completion
if the directory name initially supplied does not exist.
- dotglob
-
If set,
bash
includes filenames beginning with a `.' in the results of pathname
expansion.
- execfail
-
If set, a non-interactive shell will not exit if
it cannot execute the file specified as an argument to the
exec
builtin command. An interactive shell does not exit if
exec
fails.
- expand_aliases
-
If set, aliases are expanded as described above under
ALIASES.
This option is enabled by default for interactive shells.
- extdebug
-
If set, behavior intended for use by debuggers is enabled:
-
- 1.
-
The -F option to the declare builtin displays the source
file name and line number corresponding to each function name supplied
as an argument.
- 2.
-
If the command run by the DEBUG trap returns a non-zero value, the
next command is skipped and not executed.
- 3.
-
If the command run by the DEBUG trap returns a value of 2, and the
shell is executing in a subroutine (a shell function or a shell script
executed by the . or source builtins), a call to
return is simulated.
- 4.
-
BASH_ARGC
and
BASH_ARGV
are updated as described in their descriptions above.
- 5.
-
Function tracing is enabled: command substitution, shell functions, and
subshells invoked with ( command ) inherit the
DEBUG and RETURN traps.
- 6.
-
Error tracing is enabled: command substitution, shell functions, and
subshells invoked with ( command ) inherit the
ERR trap.
- extglob
-
If set, the extended pattern matching features described above under
Pathname Expansion are enabled.
- extquote
-
If set, $aqstringaq and $"string" quoting is
performed within ${parameter} expansions
enclosed in double quotes. This option is enabled by default.
- failglob
-
If set, patterns which fail to match filenames during pathname expansion
result in an expansion error.
- force_fignore
-
If set, the suffixes specified by the
FIGNORE
shell variable
cause words to be ignored when performing word completion even if
the ignored words are the only possible completions.
See
SHELL VARIABLES
above for a description of
FIGNORE.
This option is enabled by default.
- globasciiranges
-
If set, range expressions used in pattern matching bracket expressions (see
Pattern Matching
above) behave as if in the traditional C locale when performing
comparisons. That is, the current locale's collating sequence
is not taken into account, so
b
will not collate between
A
and
B,
and upper-case and lower-case ASCII characters will collate together.
- globstar
-
If set, the pattern ** used in a pathname expansion context will
match all files and zero or more directories and subdirectories.
If the pattern is followed by a /, only directories and
subdirectories match.
- gnu_errfmt
-
If set, shell error messages are written in the standard GNU error
message format.
- histappend
-
If set, the history list is appended to the file named by the value
of the
HISTFILE
variable when the shell exits, rather than overwriting the file.
- histreedit
-
If set, and
readline
is being used, a user is given the opportunity to re-edit a
failed history substitution.
- histverify
-
If set, and
readline
is being used, the results of history substitution are not immediately
passed to the shell parser. Instead, the resulting line is loaded into
the readline editing buffer, allowing further modification.
- hostcomplete
-
If set, and
readline
is being used, bash will attempt to perform hostname completion when a
word containing a @ is being completed (see
Completing
under
READLINE
above).
This is enabled by default.
- huponexit
-
If set, bash will send
SIGHUP
to all jobs when an interactive login shell exits.
- interactive_comments
-
If set, allow a word beginning with
#
to cause that word and all remaining characters on that
line to be ignored in an interactive shell (see
COMMENTS
above). This option is enabled by default.
- lastpipe
-
If set, and job control is not active, the shell runs the last command of
a pipeline not executed in the background in the current shell environment.
- lithist
-
If set, and the
cmdhist
option is enabled, multi-line commands are saved to the history with
embedded newlines rather than using semicolon separators where possible.
- login_shell
-
The shell sets this option if it is started as a login shell (see
INVOCATION
above).
The value may not be changed.
- mailwarn
-
If set, and a file that bash is checking for mail has been
accessed since the last time it was checked, the message ``The mail in
mailfile has been read'' is displayed.
- no_empty_cmd_completion
-
If set, and
readline
is being used,
bash
will not attempt to search the
PATH
for possible completions when
completion is attempted on an empty line.
- nocaseglob
-
If set,
bash
matches filenames in a case-insensitive fashion when performing pathname
expansion (see
Pathname Expansion
above).
- nocasematch
-
If set,
bash
matches patterns in a case-insensitive fashion when performing matching
while executing case or [[ conditional commands.
- nullglob
-
If set,
bash
allows patterns which match no
files (see
Pathname Expansion
above)
to expand to a null string, rather than themselves.
- progcomp
-
If set, the programmable completion facilities (see
Programmable Completion above) are enabled.
This option is enabled by default.
- promptvars
-
If set, prompt strings undergo
parameter expansion, command substitution, arithmetic
expansion, and quote removal after being expanded as described in
PROMPTING
above. This option is enabled by default.
- restricted_shell
-
The shell sets this option if it is started in restricted mode (see
RESTRICTED SHELL
below).
The value may not be changed.
This is not reset when the startup files are executed, allowing
the startup files to discover whether or not a shell is restricted.
- shift_verbose
-
If set, the
shift
builtin prints an error message when the shift count exceeds the
number of positional parameters.
- sourcepath
-
If set, the
source (.) builtin uses the value of
PATH
to find the directory containing the file supplied as an argument.
This option is enabled by default.
- xpg_echo
-
If set, the echo builtin expands backslash-escape sequences
by default.
- suspend [-f]
-
Suspend the execution of this shell until it receives a
SIGCONT
signal. A login shell cannot be suspended; the
-f
option can be used to override this and force the suspension.
The return status is 0 unless the shell is a login shell and
-f
is not supplied, or if job control is not enabled.
- test expr
-
- [ expr ]
-
Return a status of 0 (true) or 1 (false) depending on
the evaluation of the conditional expression
expr.
Each operator and operand must be a separate argument.
Expressions are composed of the primaries described above under
CONDITIONAL EXPRESSIONS.
test does not accept any options, nor does it accept and ignore
an argument of -- as signifying the end of options.
Expressions may be combined using the following operators, listed
in decreasing order of precedence.
The evaluation depends on the number of arguments; see below.
Operator precedence is used when there are five or more arguments.
-
- ! expr
-
True if
expr
is false.
- ( expr )
-
Returns the value of expr.
This may be used to override the normal precedence of operators.
- expr1 -a expr2
-
True if both
expr1
and
expr2
are true.
- expr1 -o expr2
-
True if either
expr1
or
expr2
is true.
test and [ evaluate conditional
expressions using a set of rules based on the number of arguments.
- 0 arguments
-
The expression is false.
- 1 argument
-
The expression is true if and only if the argument is not null.
- 2 arguments
-
If the first argument is !, the expression is true if and
only if the second argument is null.
If the first argument is one of the unary conditional operators listed above
under
CONDITIONAL EXPRESSIONS,
the expression is true if the unary test is true.
If the first argument is not a valid unary conditional operator, the expression
is false.
- 3 arguments
-
The following conditions are applied in the order listed.
If the second argument is one of the binary conditional operators listed above
under
CONDITIONAL EXPRESSIONS,
the result of the expression is the result of the binary test using
the first and third arguments as operands.
The -a and -o operators are considered binary operators
when there are three arguments.
If the first argument is !, the value is the negation of
the two-argument test using the second and third arguments.
If the first argument is exactly ( and the third argument is
exactly ), the result is the one-argument test of the second
argument.
Otherwise, the expression is false.
- 4 arguments
-
If the first argument is !, the result is the negation of
the three-argument expression composed of the remaining arguments.
Otherwise, the expression is parsed and evaluated according to
precedence using the rules listed above.
- 5 or more arguments
-
The expression is parsed and evaluated according to precedence
using the rules listed above.
When used with test or [, the < and > operators
sort lexicographically using ASCII ordering.
- times
-
Print the accumulated user and system times for the shell and
for processes run from the shell. The return status is 0.
- trap [-lp] [[arg] sigspec ...]
-
The command
arg
is to be read and executed when the shell receives
signal(s)
sigspec.
If
arg
is absent (and there is a single sigspec) or
-,
each specified signal is
reset to its original disposition (the value it had
upon entrance to the shell).
If
arg
is the null string the signal specified by each
sigspec
is ignored by the shell and by the commands it invokes.
If
arg
is not present and
-p
has been supplied, then the trap commands associated with each
sigspec
are displayed.
If no arguments are supplied or if only
-p
is given,
trap
prints the list of commands associated with each signal.
The
-l
option causes the shell to print a list of signal names and
their corresponding numbers.
Each
sigspec
is either
a signal name defined in <signal.h>, or a signal number.
Signal names are case insensitive and the
SIG
prefix is optional.
If a
sigspec
is
EXIT
(0) the command
arg
is executed on exit from the shell.
If a
sigspec
is
DEBUG,
the command
arg
is executed before every simple command, for command,
case command, select command, every arithmetic for
command, and before the first command executes in a shell function (see
SHELL GRAMMAR
above).
Refer to the description of the extdebug option to the
shopt builtin for details of its effect on the DEBUG trap.
If a
sigspec
is
RETURN,
the command
arg
is executed each time a shell function or a script executed with
the . or source builtins finishes executing.
If a
sigspec
is
ERR,
the command
arg
is executed whenever a
a pipeline (which may consist of a single simple
command), a list, or a compound command returns a
non-zero exit status,
subject to the following conditions.
The
ERR
trap is not executed if the failed
command is part of the command list immediately following a
while
or
until
keyword,
part of the test in an
if
statement, part of a command executed in a
&&
or
||
list except the command following the final && or ||,
any command in a pipeline but the last,
or if the command's return value is
being inverted using
!.
These are the same conditions obeyed by the errexit (-e) option.
Signals ignored upon entry to the shell cannot be trapped or reset.
Trapped signals that are not being ignored are reset to their original
values in a subshell or subshell environment when one is created.
The return status is false if any
sigspec
is invalid; otherwise
trap
returns true.
- type [-aftpP] name [name ...]
-
With no options,
indicate how each
name
would be interpreted if used as a command name.
If the
-t
option is used,
type
prints a string which is one of
alias,
keyword,
function,
builtin,
or
file
if
name
is an alias, shell reserved word, function, builtin, or disk file,
respectively.
If the
name
is not found, then nothing is printed, and an exit status of false
is returned.
If the
-p
option is used,
type
either returns the name of the disk file
that would be executed if
name
were specified as a command name,
or nothing if
type -t name
would not return
file.
The
-P
option forces a
PATH
search for each name, even if
type -t name
would not return
file.
If a command is hashed,
-p
and
-P
print the hashed value, which is not necessarily the file that appears
first in
PATH.
If the
-a
option is used,
type
prints all of the places that contain
an executable named
name.
This includes aliases and functions,
if and only if the
-p
option is not also used.
The table of hashed commands is not consulted
when using
-a.
The
-f
option suppresses shell function lookup, as with the command builtin.
type
returns true if all of the arguments are found, false if
any are not found.
- ulimit [-HSTabcdefilmnpqrstuvx [limit]]
-
Provides control over the resources available to the shell and to
processes started by it, on systems that allow such control.
The -H and -S options specify that the hard or soft limit is
set for the given resource.
A hard limit cannot be increased by a non-root user once it is set;
a soft limit may be increased up to the value of the hard limit.
If neither -H nor -S is specified, both the soft and hard
limits are set.
The value of
limit
can be a number in the unit specified for the resource
or one of the special values
hard,
soft,
or
unlimited,
which stand for the current hard limit, the current soft limit, and
no limit, respectively.
If
limit
is omitted, the current value of the soft limit of the resource is
printed, unless the -H option is given. When more than one
resource is specified, the limit name and unit are printed before the value.
Other options are interpreted as follows:
-
- -a
-
All current limits are reported
- -b
-
The maximum socket buffer size
- -c
-
The maximum size of core files created
- -d
-
The maximum size of a process's data segment
- -e
-
The maximum scheduling priority ("nice")
- -f
-
The maximum size of files written by the shell and its children
- -i
-
The maximum number of pending signals
- -l
-
The maximum size that may be locked into memory
- -m
-
The maximum resident set size (many systems do not honor this limit)
- -n
-
The maximum number of open file descriptors (most systems do not
allow this value to be set)
- -p
-
The pipe size in 512-byte blocks (this may not be set)
- -q
-
The maximum number of bytes in POSIX message queues
- -r
-
The maximum real-time scheduling priority
- -s
-
The maximum stack size
- -t
-
The maximum amount of cpu time in seconds
- -u
-
The maximum number of processes available to a single user
- -v
-
The maximum amount of virtual memory available to the shell and, on
some systems, to its children
- -x
-
The maximum number of file locks
- -T
-
The maximum number of threads
If
limit
is given, and the
-a
option is not used,
limit is the new value of the specified resource.
If no option is given, then
-f
is assumed. Values are in 1024-byte increments, except for
-t,
which is in seconds;
-p,
which is in units of 512-byte blocks;
and
-T,
-b,
-n,
and
-u,
which are unscaled values.
The return status is 0 unless an invalid option or argument is supplied,
or an error occurs while setting a new limit.
- umask [-p] [-S] [mode]
-
The user file-creation mask is set to
mode.
If
mode
begins with a digit, it
is interpreted as an octal number; otherwise
it is interpreted as a symbolic mode mask similar
to that accepted by
chmod(1).
If
mode
is omitted, the current value of the mask is printed.
The
-S
option causes the mask to be printed in symbolic form; the
default output is an octal number.
If the
-p
option is supplied, and
mode
is omitted, the output is in a form that may be reused as input.
The return status is 0 if the mode was successfully changed or if
no mode argument was supplied, and false otherwise.
- unalias [-a] [name ...]
-
Remove each name from the list of defined aliases. If
-a
is supplied, all alias definitions are removed. The return
value is true unless a supplied
name
is not a defined alias.
- unset [-fv] [-n] [name ...]
-
For each
name,
remove the corresponding variable or function.
If the
-v
option is given, each
name
refers to a shell variable, and that variable is removed.
Read-only variables may not be unset.
If
-f
is specified, each
name
refers to a shell function, and the function definition
is removed.
If the
-n
option is supplied, and name is a variable with the nameref
attribute, name will be unset rather than the variable it
references.
-n has no effect if the -f option is supplied.
If no options are supplied, each name refers to a variable; if
there is no variable by that name, any function with that name is
unset.
Each unset variable or function is removed from the environment
passed to subsequent commands.
If any of
COMP_WORDBREAKS,
RANDOM,
SECONDS,
LINENO,
HISTCMD,
FUNCNAME,
GROUPS,
or
DIRSTACK
are unset, they lose their special properties, even if they are
subsequently reset. The exit status is true unless a
name
is readonly.
- wait [-n] [n ...]
-
Wait for each specified child process and return its termination status.
Each
n
may be a process
ID or a job specification; if a job spec is given, all processes
in that job's pipeline are waited for. If
n
is not given, all currently active child processes
are waited for, and the return status is zero.
If the -n option is supplied, wait waits for any job to
terminate and returns its exit status.
If
n
specifies a non-existent process or job, the return status is
127. Otherwise, the return status is the exit status of the last
process or job waited for.
RESTRICTED SHELL
If
bash
is started with the name
rbash,
or the
-r
option is supplied at invocation,
the shell becomes restricted.
A restricted shell is used to
set up an environment more controlled than the standard shell.
It behaves identically to
bash
with the exception that the following are disallowed or not performed:
- *
-
changing directories with cd
- *
-
setting or unsetting the values of
SHELL,
PATH,
ENV,
or
BASH_ENV
- *
-
specifying command names containing
/
- *
-
specifying a filename containing a
/
as an argument to the
.
builtin command
- *
-
specifying a filename containing a slash as an argument to the
-p
option to the
hash
builtin command
- *
-
importing function definitions from the shell environment at startup
- *
-
parsing the value of
SHELLOPTS
from the shell environment at startup
- *
-
redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
- *
-
using the
exec
builtin command to replace the shell with another command
- *
-
adding or deleting builtin commands with the
-f
and
-d
options to the
enable
builtin command
- *
-
using the enable builtin command to enable disabled shell builtins
- *
-
specifying the
-p
option to the
command
builtin command
- *
-
turning off restricted mode with
set +r or set +o restricted.
These restrictions are enforced after any startup files are read.
When a command that is found to be a shell script is executed
(see
COMMAND EXECUTION
above),
rbash
turns off any restrictions in the shell spawned to execute the
script.
SEE ALSO
- Bash Reference Manual, Brian Fox and Chet Ramey
-
- The Gnu Readline Library, Brian Fox and Chet Ramey
-
- The Gnu History Library, Brian Fox and Chet Ramey
-
- Portable Operating System Interface (POSIX) Part 2: Shell and Utilities, IEEE --
-
http://pubs.opengroup.org/onlinepubs/9699919799/
- http://tiswww.case.edu/~chet/bash/POSIX -- a description of posix mode
-
- sh(1), ksh(1), csh(1)
-
- emacs(1), vi(1)
-
- readline(3)
-
FILES
-
/bin/bash
-
The bash executable
-
/etc/profile
-
The systemwide initialization file, executed for login shells
-
~/.bash_profile
-
The personal initialization file, executed for login shells
-
~/.bashrc
-
The individual per-interactive-shell startup file
-
~/.bash_logout
-
The individual login shell cleanup file, executed when a login shell exits
-
~/.inputrc
-
Individual readline initialization file
AUTHORS
Brian Fox, Free Software Foundation
bfox@gnu.org
Chet Ramey, Case Western Reserve University
chet.ramey@case.edu
BUG REPORTS
If you find a bug in
bash,
you should report it. But first, you should
make sure that it really is a bug, and that it appears in the latest
version of
bash.
The latest version is always available from
ftp://ftp.gnu.org/pub/gnu/bash/.
Once you have determined that a bug actually exists, use the
bashbug
command to submit a bug report.
If you have a fix, you are encouraged to mail that as well!
Suggestions and `philosophical' bug reports may be mailed
to bug-bash@gnu.org or posted to the Usenet
newsgroup
gnu.bash.bug.
ALL bug reports should include:
- The version number of bash
-
- The hardware and operating system
-
- The compiler used to compile
-
- A description of the bug behaviour
-
- A short script or `recipe' which exercises the bug
-
bashbug
inserts the first three items automatically into the template
it provides for filing a bug report.
Comments and bug reports concerning
this manual page should be directed to
chet.ramey@case.edu.
BUGS
It's too big and too slow.
There are some subtle differences between
bash
and traditional versions of
sh,
mostly because of the
POSIX
specification.
Aliases are confusing in some uses.
Shell builtin commands and functions are not stoppable/restartable.
Compound commands and command sequences of the form `a ; b ; c'
are not handled gracefully when process suspension is attempted.
When a process is stopped, the shell immediately executes the next
command in the sequence.
It suffices to place the sequence of commands between
parentheses to force it into a subshell, which may be stopped as
a unit.
Array variables may not (yet) be exported.
There may be only one active coprocess at a time.
GNU Bash 4.3 | 2014 February 2 | BASH(1)
|
Index
- NAME
-
- SYNOPSIS
-
- COPYRIGHT
-
- DESCRIPTION
-
- OPTIONS
-
- ARGUMENTS
-
- INVOCATION
-
- DEFINITIONS
-
- RESERVED WORDS
-
- SHELL GRAMMAR
-
- Simple Commands
-
- Pipelines
-
- Lists
-
- Compound Commands
-
- Coprocesses
-
- Shell Function Definitions
-
- COMMENTS
-
- QUOTING
-
- PARAMETERS
-
- Positional Parameters
-
- Special Parameters
-
- Shell Variables
-
- Arrays
-
- EXPANSION
-
- Brace Expansion
-
- Tilde Expansion
-
- Parameter Expansion
-
- Command Substitution
-
- Arithmetic Expansion
-
- Process Substitution
-
- Word Splitting
-
- Pathname Expansion
-
- Quote Removal
-
- REDIRECTION
-
- Redirecting Input
-
- Redirecting Output
-
- Appending Redirected Output
-
- Redirecting Standard Output and Standard Error
-
- Appending Standard Output and Standard Error
-
- Here Documents
-
- Here Strings
-
- Duplicating File Descriptors
-
- Moving File Descriptors
-
- Opening File Descriptors for Reading and Writing
-
- ALIASES
-
- FUNCTIONS
-
- ARITHMETIC EVALUATION
-
- CONDITIONAL EXPRESSIONS
-
- SIMPLE COMMAND EXPANSION
-
- COMMAND EXECUTION
-
- COMMAND EXECUTION ENVIRONMENT
-
- ENVIRONMENT
-
- EXIT STATUS
-
- SIGNALS
-
- JOB CONTROL
-
- PROMPTING
-
- READLINE
-
- Readline Notation
-
- Readline Initialization
-
- Readline Key Bindings
-
- Readline Variables
-
- Readline Conditional Constructs
-
- Searching
-
- Readline Command Names
-
- Commands for Moving
-
- Commands for Manipulating the History
-
- Commands for Changing Text
-
- Killing and Yanking
-
- Numeric Arguments
-
- Completing
-
- Keyboard Macros
-
- Miscellaneous
-
- Programmable Completion
-
- HISTORY
-
- HISTORY EXPANSION
-
- Event Designators
-
- Word Designators
-
- Modifiers
-
- SHELL BUILTIN COMMANDS
-
- RESTRICTED SHELL
-
- SEE ALSO
-
- FILES
-
- AUTHORS
-
- BUG REPORTS
-
- BUGS
-
This document was created by man2html from bash.1.
Time: 24 February 2014 08:28:34 EST
0707010007eb37000081a40000000000000000000000015428b7350000243f00000100000100b5ffffffffffffffff0000002400000000root/usr/local/share/doc/bash/POSIX 6.11 Bash POSIX Mode
====================
Starting Bash with the `--posix' command-line option or executing `set
-o posix' while Bash is running will cause Bash to conform more closely
to the POSIX standard by changing the behavior to match that specified
by POSIX in areas where the Bash default differs.
When invoked as `sh', Bash enters POSIX mode after reading the startup
files.
The following list is what's changed when `POSIX mode' is in effect:
1. When a command in the hash table no longer exists, Bash will
re-search `$PATH' to find the new location. This is also
available with `shopt -s checkhash'.
2. The message printed by the job control code and builtins when a job
exits with a non-zero status is `Done(status)'.
3. The message printed by the job control code and builtins when a job
is stopped is `Stopped(SIGNAME)', where SIGNAME is, for example,
`SIGTSTP'.
4. The `bg' builtin uses the required format to describe each job
placed in the background, which does not include an indication of
whether the job is the current or previous job.
5. Reserved words appearing in a context where reserved words are
recognized do not undergo alias expansion.
6. The POSIX `PS1' and `PS2' expansions of `!' to the history number
and `!!' to `!' are enabled, and parameter expansion is performed
on the values of `PS1' and `PS2' regardless of the setting of the
`promptvars' option.
7. The POSIX startup files are executed (`$ENV') rather than the
normal Bash files.
8. Tilde expansion is only performed on assignments preceding a
command name, rather than on all assignment statements on the line.
9. The `command' builtin does not prevent builtins that take
assignment statements as arguments from expanding them as
assignment statements; when not in POSIX mode, assignment builtins
lose their assignment statement expansion properties when preceded
by `command'.
10. The default history file is `~/.sh_history' (this is the default
value of `$HISTFILE').
11. The output of `kill -l' prints all the signal names on a single
line, separated by spaces, without the `SIG' prefix.
12. The `kill' builtin does not accept signal names with a `SIG'
prefix.
13. Non-interactive shells exit if FILENAME in `.' FILENAME is not
found.
14. Non-interactive shells exit if a syntax error in an arithmetic
expansion results in an invalid expression.
15. Non-interactive shells exit if there is a syntax error in a script
read with the `.' or `source' builtins, or in a string processed by
the `eval' builtin.
16. Redirection operators do not perform filename expansion on the word
in the redirection unless the shell is interactive.
17. Redirection operators do not perform word splitting on the word in
the redirection.
18. Function names must be valid shell `name's. That is, they may not
contain characters other than letters, digits, and underscores, and
may not start with a digit. Declaring a function with an invalid
name causes a fatal syntax error in non-interactive shells.
19. Function names may not be the same as one of the POSIX special
builtins.
20. POSIX special builtins are found before shell functions during
command lookup.
21. The `time' reserved word may be used by itself as a command. When
used in this way, it displays timing statistics for the shell and
its completed children. The `TIMEFORMAT' variable controls the
format of the timing information.
22. When parsing and expanding a ${...} expansion that appears within
double quotes, single quotes are no longer special and cannot be
used to quote a closing brace or other special character, unless
the operator is one of those defined to perform pattern removal.
In this case, they do not have to appear as matched pairs.
23. The parser does not recognize `time' as a reserved word if the next
token begins with a `-'.
24. If a POSIX special builtin returns an error status, a
non-interactive shell exits. The fatal errors are those listed in
the POSIX standard, and include things like passing incorrect
options, redirection errors, variable assignment errors for
assignments preceding the command name, and so on.
25. A non-interactive shell exits with an error status if a variable
assignment error occurs when no command name follows the assignment
statements. A variable assignment error occurs, for example, when
trying to assign a value to a readonly variable.
26. A non-interactive shell exits with an error status if a variable
assignment error occurs in an assignment statement preceding a
special builtin, but not with any other simple command.
27. A non-interactive shell exits with an error status if the iteration
variable in a `for' statement or the selection variable in a
`select' statement is a readonly variable.
28. Process substitution is not available.
29. While variable indirection is available, it may not be applied to
the `#' and `?' special parameters.
30. Assignment statements preceding POSIX special builtins persist in
the shell environment after the builtin completes.
31. Assignment statements preceding shell function calls persist in the
shell environment after the function returns, as if a POSIX
special builtin command had been executed.
32. The `export' and `readonly' builtin commands display their output
in the format required by POSIX.
33. The `trap' builtin displays signal names without the leading `SIG'.
34. The `trap' builtin doesn't check the first argument for a possible
signal specification and revert the signal handling to the original
disposition if it is, unless that argument consists solely of
digits and is a valid signal number. If users want to reset the
handler for a given signal to the original disposition, they
should use `-' as the first argument.
35. The `.' and `source' builtins do not search the current directory
for the filename argument if it is not found by searching `PATH'.
36. Subshells spawned to execute command substitutions inherit the
value of the `-e' option from the parent shell. When not in POSIX
mode, Bash clears the `-e' option in such subshells.
37. Alias expansion is always enabled, even in non-interactive shells.
38. When the `alias' builtin displays alias definitions, it does not
display them with a leading `alias ' unless the `-p' option is
supplied.
39. When the `set' builtin is invoked without options, it does not
display shell function names and definitions.
40. When the `set' builtin is invoked without options, it displays
variable values without quotes, unless they contain shell
metacharacters, even if the result contains nonprinting characters.
41. When the `cd' builtin is invoked in LOGICAL mode, and the pathname
constructed from `$PWD' and the directory name supplied as an
argument does not refer to an existing directory, `cd' will fail
instead of falling back to PHYSICAL mode.
42. The `pwd' builtin verifies that the value it prints is the same as
the current directory, even if it is not asked to check the file
system with the `-P' option.
43. When listing the history, the `fc' builtin does not include an
indication of whether or not a history entry has been modified.
44. The default editor used by `fc' is `ed'.
45. The `type' and `command' builtins will not report a non-executable
file as having been found, though the shell will attempt to
execute such a file if it is the only so-named file found in
`$PATH'.
46. The `vi' editing mode will invoke the `vi' editor directly when
the `v' command is run, instead of checking `$VISUAL' and
`$EDITOR'.
47. When the `xpg_echo' option is enabled, Bash does not attempt to
interpret any arguments to `echo' as options. Each argument is
displayed, after escape characters are converted.
48. The `ulimit' builtin uses a block size of 512 bytes for the `-c'
and `-f' options.
49. The arrival of `SIGCHLD' when a trap is set on `SIGCHLD' does not
interrupt the `wait' builtin and cause it to return immediately.
The trap command is run once for each child that exits.
50. The `read' builtin may be interrupted by a signal for which a trap
has been set. If Bash receives a trapped signal while executing
`read', the trap handler executes and `read' returns an exit
status greater than 128.
There is other POSIX behavior that Bash does not implement by default
even when in POSIX mode. Specifically:
1. The `fc' builtin checks `$EDITOR' as a program to edit history
entries if `FCEDIT' is unset, rather than defaulting directly to
`ed'. `fc' uses `ed' if `EDITOR' is unset.
2. As noted above, Bash requires the `xpg_echo' option to be enabled
for the `echo' builtin to be fully conformant.
Bash can be configured to be POSIX-conformant by default, by specifying
the `--enable-strict-posix-default' to `configure' when building (*note
Optional Features::).
0707010007eb3b000081a40000000000000000000000015428b735000cd94400000100000100b5ffffffffffffffff0000002b00000000root/usr/local/share/doc/bash/bashref.html
Bash Reference Manual:
Bash Reference Manual
This text is a brief description of the features that are present in
the Bash shell (version 4.3, 2 February 2014).
The Bash home page is http://www.gnu.org/software/bash/.
This is Edition 4.3, last updated 2 February 2014,
of The GNU Bash Reference Manual,
for Bash
, Version 4.3.
Bash contains features that appear in other popular shells, and some
features that only appear in Bash. Some of the shells that Bash has
borrowed concepts from are the Bourne Shell (`sh'), the Korn Shell
(`ksh'), and the C-shell (`csh' and its successor,
`tcsh'). The following menu breaks the features up into
categories, noting which features were inspired by other shells and
which are specific to Bash.
This manual is meant as a brief introduction to features found in
Bash. The Bash manual page should be used as the definitive
reference on shell behavior.
1. Introduction
1.1 What is Bash?
Bash is the shell, or command language interpreter,
for the GNU operating system.
The name is an acronym for the `Bourne-Again SHell',
a pun on Stephen Bourne, the author of the direct ancestor of
the current Unix shell sh
,
which appeared in the Seventh Edition Bell Labs Research version
of Unix.
Bash is largely compatible with sh
and incorporates useful
features from the Korn shell ksh
and the C shell csh
.
It is intended to be a conformant implementation of the IEEE
POSIX Shell and Tools portion of the IEEE POSIX
specification (IEEE Standard 1003.1).
It offers functional improvements over sh
for both interactive and
programming use.
While the GNU operating system provides other shells, including
a version of csh
, Bash is the default shell.
Like other GNU software, Bash is quite portable. It currently runs
on nearly every version of Unix and a few other operating systems -
independently-supported ports exist for MS-DOS, OS/2,
and Windows platforms.
1.2 What is a shell?
At its base, a shell is simply a macro processor that executes
commands. The term macro processor means functionality where text
and symbols are expanded to create larger expressions.
A Unix shell is both a command interpreter and a programming
language. As a command interpreter, the shell provides the user
interface to the rich set of GNU utilities. The programming
language features allow these utilities to be combined.
Files containing commands can be created, and become
commands themselves. These new commands have the same status as
system commands in directories such as `/bin', allowing users
or groups to establish custom environments to automate their common
tasks.
Shells may be used interactively or non-interactively. In
interactive mode, they accept input typed from the keyboard.
When executing non-interactively, shells execute commands read
from a file.
A shell allows execution of GNU commands, both synchronously and
asynchronously.
The shell waits for synchronous commands to complete before accepting
more input; asynchronous commands continue to execute in parallel
with the shell while it reads and executes additional commands.
The redirection constructs permit
fine-grained control of the input and output of those commands.
Moreover, the shell allows control over the contents of commands'
environments.
Shells also provide a small set of built-in
commands (builtins) implementing functionality impossible
or inconvenient to obtain via separate utilities.
For example, cd
, break
, continue
, and
exec
cannot be implemented outside of the shell because
they directly manipulate the shell itself.
The history
, getopts
, kill
, or pwd
builtins, among others, could be implemented in separate utilities,
but they are more convenient to use as builtin commands.
All of the shell builtins are described in
subsequent sections.
While executing commands is essential, most of the power (and
complexity) of shells is due to their embedded programming
languages. Like any high-level language, the shell provides
variables, flow control constructs, quoting, and functions.
Shells offer features geared specifically for
interactive use rather than to augment the programming language.
These interactive features include job control, command line
editing, command history and aliases. Each of these features is
described in this manual.
2. Definitions
These definitions are used throughout the remainder of this manual.
POSIX
-
A family of open system standards based on Unix. Bash
is primarily concerned with the Shell and Utilities portion of the
POSIX 1003.1 standard.
blank
- A space or tab character.
builtin
-
A command that is implemented internally by the shell itself, rather
than by an executable program somewhere in the file system.
control operator
-
A
token
that performs a control function. It is a newline
or one of the following:
`||', `&&', `&', `;', `;;',
`|', `|&', `(', or `)'.
exit status
-
The value returned by a command to its caller. The value is restricted
to eight bits, so the maximum value is 255.
field
-
A unit of text that is the result of one of the shell expansions. After
expansion, when executing a command, the resulting fields are used as
the command name and arguments.
filename
-
A string of characters used to identify a file.
job
-
A set of processes comprising a pipeline, and any processes descended
from it, that are all in the same process group.
job control
-
A mechanism by which users can selectively stop (suspend) and restart
(resume) execution of processes.
metacharacter
-
A character that, when unquoted, separates words. A metacharacter is
a
blank
or one of the following characters:
`|', `&', `;', `(', `)', `<', or
`>'.
name
-
A
word
consisting solely of letters, numbers, and underscores,
and beginning with a letter or underscore. Name
s are used as
shell variable and function names.
Also referred to as an identifier
.
operator
-
A
control operator
or a redirection operator
.
See section 3.6 Redirections, for a list of redirection operators.
Operators contain at least one unquoted metacharacter
.
process group
-
A collection of related processes each having the same process
group ID.
process group ID
-
A unique identifier that represents a
process group
during its lifetime.
reserved word
-
A
word
that has a special meaning to the shell. Most reserved
words introduce shell flow control constructs, such as for
and
while
.
return status
-
A synonym for
exit status
.
signal
-
A mechanism by which a process may be notified by the kernel
of an event occurring in the system.
special builtin
-
A shell builtin command that has been classified as special by the
POSIX standard.
token
-
A sequence of characters considered a single unit by the shell.
It is either a
word
or an operator
.
word
-
A sequence of characters treated as a unit by the shell.
Words may not include unquoted
metacharacters
.
3. Basic Shell Features
Bash is an acronym for `Bourne-Again SHell'.
The Bourne shell is
the traditional Unix shell originally written by Stephen Bourne.
All of the Bourne shell builtin commands are available in Bash,
The rules for evaluation and quoting are taken from the POSIX
specification for the `standard' Unix shell.
This chapter briefly summarizes the shell's `building blocks':
commands, control structures, shell functions, shell parameters,
shell expansions,
redirections, which are a way to direct input and output from
and to named files, and how the shell executes commands.
3.1 Shell Syntax
When the shell reads input, it proceeds through a
sequence of operations. If the input indicates the beginning of a
comment, the shell ignores the comment symbol (`#'), and the rest
of that line.
Otherwise, roughly speaking, the shell reads its input and
divides the input into words and operators, employing the quoting rules
to select which meanings to assign various words and characters.
The shell then parses these tokens into commands and other constructs,
removes the special meaning of certain words or characters, expands
others, redirects input and output as needed, executes the specified
command, waits for the command's exit status, and makes that exit status
available for further inspection or processing.
3.1.1 Shell Operation
The following is a brief description of the shell's operation when it
reads and executes a command. Basically, the shell does the
following:
-
Reads its input from a file (see section 3.8 Shell Scripts), from a string
supplied as an argument to the `-c' invocation option
(see section 6.1 Invoking Bash), or from the user's terminal.
-
Breaks the input into words and operators, obeying the quoting rules
described in 3.1.2 Quoting. These tokens are separated by
metacharacters
. Alias expansion is performed by this step
(see section 6.6 Aliases).
-
Parses the tokens into simple and compound commands
(see section 3.2 Shell Commands).
-
Performs the various shell expansions (see section 3.5 Shell Expansions), breaking
the expanded tokens into lists of filenames (see section 3.5.8 Filename Expansion)
and commands and arguments.
-
Performs any necessary redirections (see section 3.6 Redirections) and removes
the redirection operators and their operands from the argument list.
-
Executes the command (see section 3.7 Executing Commands).
-
Optionally waits for the command to complete and collects its exit
status (see section 3.7.5 Exit Status).
3.1.2 Quoting
Quoting is used to remove the special meaning of certain
characters or words to the shell. Quoting can be used to
disable special treatment for special characters, to prevent
reserved words from being recognized as such, and to prevent
parameter expansion.
Each of the shell metacharacters (see section 2. Definitions)
has special meaning to the shell and must be quoted if it is to
represent itself.
When the command history expansion facilities are being used
(see section 9.3 History Expansion), the
history expansion character, usually `!', must be quoted
to prevent history expansion. See section 9.1 Bash History Facilities, for
more details concerning history expansion.
There are three quoting mechanisms: the
escape character, single quotes, and double quotes.
3.1.2.1 Escape Character
A non-quoted backslash `\' is the Bash escape character.
It preserves the literal value of the next character that follows,
with the exception of newline
. If a \newline
pair
appears, and the backslash itself is not quoted, the \newline
is treated as a line continuation (that is, it is removed from
the input stream and effectively ignored).
3.1.2.2 Single Quotes
Enclosing characters in single quotes (`'') preserves the literal value
of each character within the quotes. A single quote may not occur
between single quotes, even when preceded by a backslash.
3.1.2.3 Double Quotes
Enclosing characters in double quotes (`"') preserves the literal value
of all characters within the quotes, with the exception of
`$', ``', `\',
and, when history expansion is enabled, `!'.
The characters `$' and ``'
retain their special meaning within double quotes (see section 3.5 Shell Expansions).
The backslash retains its special meaning only when followed by one of
the following characters:
`$', ``', `"', `\', or newline
.
Within double quotes, backslashes that are followed by one of these
characters are removed. Backslashes preceding characters without a
special meaning are left unmodified.
A double quote may be quoted within double quotes by preceding it with
a backslash.
If enabled, history expansion will be performed unless an `!'
appearing in double quotes is escaped using a backslash.
The backslash preceding the `!' is not removed.
The special parameters `*' and `@' have special meaning
when in double quotes (see section 3.5.3 Shell Parameter Expansion).
3.1.2.4 ANSI-C Quoting
Words of the form $'string'
are treated specially. The
word expands to string, with backslash-escaped characters replaced
as specified by the ANSI C standard. Backslash escape sequences, if
present, are decoded as follows:
\a
- alert (bell)
\b
- backspace
\e
\E
- an escape character (not ANSI C)
\f
- form feed
\n
- newline
\r
- carriage return
\t
- horizontal tab
\v
- vertical tab
\\
- backslash
\'
- single quote
\"
- double quote
\nnn
- the eight-bit character whose value is the octal value nnn
(one to three digits)
\xHH
- the eight-bit character whose value is the hexadecimal value HH
(one or two hex digits)
\uHHHH
- the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
HHHH (one to four hex digits)
\UHHHHHHHH
- the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
HHHHHHHH (one to eight hex digits)
\cx
- a control-x character
The expanded result is single-quoted, as if the dollar sign had not
been present.
3.1.2.5 Locale-Specific Translation
A double-quoted string preceded by a dollar sign (`$') will cause
the string to be translated according to the current locale.
If the current locale is C
or POSIX
, the dollar sign
is ignored.
If the string is translated and replaced, the replacement is
double-quoted.
Some systems use the message catalog selected by the LC_MESSAGES
shell variable. Others create the name of the message catalog from the
value of the TEXTDOMAIN
shell variable, possibly adding a
suffix of `.mo'. If you use the TEXTDOMAIN
variable, you
may need to set the TEXTDOMAINDIR
variable to the location of
the message catalog files. Still others use both variables in this
fashion:
TEXTDOMAINDIR
/LC_MESSAGES
/LC_MESSAGES/TEXTDOMAIN
.mo.
3.1.3 Comments
In a non-interactive shell, or an interactive shell in which the
interactive_comments
option to the shopt
builtin is enabled (see section 4.3.2 The Shopt Builtin),
a word beginning with `#'
causes that word and all remaining characters on that line to
be ignored. An interactive shell without the interactive_comments
option enabled does not allow comments. The interactive_comments
option is on by default in interactive shells.
See section 6.3 Interactive Shells, for a description of what makes
a shell interactive.
3.2 Shell Commands
A simple shell command such as echo a b c
consists of the command
itself followed by arguments, separated by spaces.
More complex shell commands are composed of simple commands arranged together
in a variety of ways: in a pipeline in which the output of one command
becomes the input of a second, in a loop or conditional construct, or in
some other grouping.
3.2.1 Simple Commands
A simple command is the kind of command encountered most often.
It's just a sequence of words separated by blank
s, terminated
by one of the shell's control operators (see section 2. Definitions). The
first word generally specifies a command to be executed, with the
rest of the words being that command's arguments.
The return status (see section 3.7.5 Exit Status) of a simple command is
its exit status as provided
by the POSIX 1003.1 waitpid
function, or 128+n if
the command was terminated by signal n.
3.2.2 Pipelines
A pipeline
is a sequence of simple commands separated by one of
the control operators `|' or `|&'.
The format for a pipeline is
| [time [-p]] [!] command1 [ | or |& command2 ] ...
|
The output of each command in the pipeline is connected via a pipe
to the input of the next command.
That is, each command reads the previous command's output. This
connection is performed before any redirections specified by the
command.
If `|&' is used, command1's standard error, in addition to
its standard output, is connected to
command2's standard input through the pipe;
it is shorthand for 2>&1 |
.
This implicit redirection of the standard error to the standard output is
performed after any redirections specified by the command.
The reserved word time
causes timing statistics
to be printed for the pipeline once it finishes.
The statistics currently consist of elapsed (wall-clock) time and
user and system time consumed by the command's execution.
The `-p' option changes the output format to that specified
by POSIX.
When the shell is in POSIX mode (see section 6.11 Bash POSIX Mode),
it does not recognize time
as a reserved word if the next
token begins with a `-'.
The TIMEFORMAT
variable may be set to a format string that
specifies how the timing information should be displayed.
See section 5.2 Bash Variables, for a description of the available formats.
The use of time
as a reserved word permits the timing of
shell builtins, shell functions, and pipelines. An external
time
command cannot time these easily.
When the shell is in POSIX mode (see section 6.11 Bash POSIX Mode), time
may be followed by a newline. In this case, the shell displays the
total user and system time consumed by the shell and its children.
The TIMEFORMAT
variable may be used to specify the format of
the time information.
If the pipeline is not executed asynchronously (see section 3.2.3 Lists of Commands), the
shell waits for all commands in the pipeline to complete.
Each command in a pipeline is executed in its own subshell
(see section 3.7.3 Command Execution Environment). The exit
status of a pipeline is the exit status of the last command in the
pipeline, unless the pipefail
option is enabled
(see section 4.3.1 The Set Builtin).
If pipefail
is enabled, the pipeline's return status is the
value of the last (rightmost) command to exit with a non-zero status,
or zero if all commands exit successfully.
If the reserved word `!' precedes the pipeline, the
exit status is the logical negation of the exit status as described
above.
The shell waits for all commands in the pipeline to terminate before
returning a value.
3.2.3 Lists of Commands
A list
is a sequence of one or more pipelines separated by one
of the operators `;', `&', `&&', or `||',
and optionally terminated by one of `;', `&', or a
newline
.
Of these list operators, `&&' and `||'
have equal precedence, followed by `;' and `&',
which have equal precedence.
A sequence of one or more newlines may appear in a list
to delimit commands, equivalent to a semicolon.
If a command is terminated by the control operator `&',
the shell executes the command asynchronously in a subshell.
This is known as executing the command in the background.
The shell does not wait for the command to finish, and the return
status is 0 (true).
When job control is not active (see section 7. Job Control),
the standard input for asynchronous commands, in the absence of any
explicit redirections, is redirected from /dev/null
.
Commands separated by a `;' are executed sequentially; the shell
waits for each command to terminate in turn. The return status is the
exit status of the last command executed.
AND and OR lists are sequences of one or more pipelines
separated by the control operators `&&' and `||',
respectively. AND and OR lists are executed with left
associativity.
An AND list has the form
command2 is executed if, and only if, command1
returns an exit status of zero.
An OR list has the form
command2 is executed if, and only if, command1
returns a non-zero exit status.
The return status of
AND and OR lists is the exit status of the last command
executed in the list.
3.2.4 Compound Commands
Compound commands are the shell programming constructs.
Each construct begins with a reserved word or control operator and is
terminated by a corresponding reserved word or operator.
Any redirections (see section 3.6 Redirections) associated with a compound command
apply to all commands within that compound command unless explicitly overridden.
In most cases a list of commands in a compound command's description may be
separated from the rest of the command by one or more newlines, and may be
followed by a newline in place of a semicolon.
Bash provides looping constructs, conditional commands, and mechanisms
to group commands and execute them as a unit.
3.2.4.1 Looping Constructs
Bash supports the following looping constructs.
Note that wherever a `;' appears in the description of a
command's syntax, it may be replaced with one or more newlines.
until
-
The syntax of the
until
command is:
| until test-commands; do consequent-commands; done
|
Execute consequent-commands as long as
test-commands has an exit status which is not zero.
The return status is the exit status of the last command executed
in consequent-commands, or zero if none was executed.
while
-
The syntax of the
while
command is:
| while test-commands; do consequent-commands; done
|
Execute consequent-commands as long as
test-commands has an exit status of zero.
The return status is the exit status of the last command executed
in consequent-commands, or zero if none was executed.
for
-
The syntax of the
for
command is:
| for name [ [in [words ...] ] ; ] do commands; done
|
Expand words, and execute commands once for each member
in the resultant list, with name bound to the current member.
If `in words' is not present, the for
command
executes the commands once for each positional parameter that is
set, as if `in "$@"' had been specified
(see section 3.4.2 Special Parameters).
The return status is the exit status of the last command that executes.
If there are no items in the expansion of words, no commands are
executed, and the return status is zero.
An alternate form of the for
command is also supported:
| for (( expr1 ; expr2 ; expr3 )) ; do commands ; done
|
First, the arithmetic expression expr1 is evaluated according
to the rules described below (see section 6.5 Shell Arithmetic).
The arithmetic expression expr2 is then evaluated repeatedly
until it evaluates to zero.
Each time expr2 evaluates to a non-zero value, commands are
executed and the arithmetic expression expr3 is evaluated.
If any expression is omitted, it behaves as if it evaluates to 1.
The return value is the exit status of the last command in commands
that is executed, or false if any of the expressions is invalid.
The break
and continue
builtins (see section 4.1 Bourne Shell Builtins)
may be used to control loop execution.
3.2.4.2 Conditional Constructs
if
-
The syntax of the
if
command is:
| if test-commands; then
consequent-commands;
[elif more-test-commands; then
more-consequents;]
[else alternate-consequents;]
fi
|
The test-commands list is executed, and if its return status is zero,
the consequent-commands list is executed.
If test-commands returns a non-zero status, each elif
list
is executed in turn, and if its exit status is zero,
the corresponding more-consequents is executed and the
command completes.
If `else alternate-consequents' is present, and
the final command in the final if
or elif
clause
has a non-zero exit status, then alternate-consequents is executed.
The return status is the exit status of the last command executed, or
zero if no condition tested true.
case
-
The syntax of the
case
command is:
| case word in [ [(] pattern [| pattern]...) command-list ;;]... esac
|
case
will selectively execute the command-list corresponding to
the first pattern that matches word.
If the shell option nocasematch
(see the description of shopt
in 4.3.2 The Shopt Builtin)
is enabled, the match is performed without regard to the case
of alphabetic characters.
The `|' is used to separate multiple patterns, and the `)'
operator terminates a pattern list.
A list of patterns and an associated command-list is known
as a clause.
Each clause must be terminated with `;;', `;&', or `;;&'.
The word undergoes tilde expansion, parameter expansion, command
substitution, arithmetic expansion, and quote removal before matching is
attempted. Each pattern undergoes tilde expansion, parameter
expansion, command substitution, and arithmetic expansion.
There may be an arbitrary number of case
clauses, each terminated
by a `;;', `;&', or `;;&'.
The first pattern that matches determines the
command-list that is executed.
It's a common idiom to use `*' as the final pattern to define the
default case, since that pattern will always match.
Here is an example using case
in a script that could be used to
describe one interesting feature of an animal:
| echo -n "Enter the name of an animal: "
read ANIMAL
echo -n "The $ANIMAL has "
case $ANIMAL in
horse | dog | cat) echo -n "four";;
man | kangaroo ) echo -n "two";;
*) echo -n "an unknown number of";;
esac
echo " legs."
|
If the `;;' operator is used, no subsequent matches are attempted after
the first pattern match.
Using `;&' in place of `;;' causes execution to continue with
the command-list associated with the next clause, if any.
Using `;;&' in place of `;;' causes the shell to test the patterns
in the next clause, if any, and execute any associated command-list
on a successful match.
The return status is zero if no pattern is matched. Otherwise, the
return status is the exit status of the command-list executed.
select
-
The select
construct allows the easy generation of menus.
It has almost the same syntax as the for
command:
| select name [in words ...]; do commands; done
|
The list of words following in
is expanded, generating a list
of items. The set of expanded words is printed on the standard
error output stream, each preceded by a number. If the
`in words' is omitted, the positional parameters are printed,
as if `in "$@"' had been specified.
The PS3
prompt is then displayed and a line is read from the
standard input.
If the line consists of a number corresponding to one of the displayed
words, then the value of name is set to that word.
If the line is empty, the words and prompt are displayed again.
If EOF
is read, the select
command completes.
Any other value read causes name to be set to null.
The line read is saved in the variable REPLY
.
The commands are executed after each selection until a
break
command is executed, at which
point the select
command completes.
Here is an example that allows the user to pick a filename from the
current directory, and displays the name and index of the file
selected.
| select fname in *;
do
echo you picked $fname \($REPLY\)
break;
done
|
((...))
The arithmetic expression is evaluated according to the rules
described below (see section 6.5 Shell Arithmetic).
If the value of the expression is non-zero, the return status is 0;
otherwise the return status is 1. This is exactly equivalent to
See section 4.2 Bash Builtin Commands, for a full description of the let
builtin.
[[...]]
-
Return a status of 0 or 1 depending on the evaluation of
the conditional expression expression.
Expressions are composed of the primaries described below in
6.4 Bash Conditional Expressions.
Word splitting and filename expansion are not performed on the words
between the [[
and ]]
; tilde expansion, parameter and
variable expansion, arithmetic expansion, command substitution, process
substitution, and quote removal are performed.
Conditional operators such as `-f' must be unquoted to be recognized
as primaries.
When used with [[
, the `<' and `>' operators sort
lexicographically using the current locale.
When the `==' and `!=' operators are used, the string to the
right of the operator is considered a pattern and matched according
to the rules described below in 3.5.8.1 Pattern Matching,
as if the extglob
shell option were enabled.
The `=' operator is identical to `=='.
If the shell option nocasematch
(see the description of shopt
in 4.3.2 The Shopt Builtin)
is enabled, the match is performed without regard to the case
of alphabetic characters.
The return value is 0 if the string matches (`==') or does not
match (`!=')the pattern, and 1 otherwise.
Any part of the pattern may be quoted to force the quoted portion
to be matched as a string.
An additional binary operator, `=~', is available, with the same
precedence as `==' and `!='.
When it is used, the string to the right of the operator is considered
an extended regular expression and matched accordingly (as in regex3)).
The return value is 0 if the string matches
the pattern, and 1 otherwise.
If the regular expression is syntactically incorrect, the conditional
expression's return value is 2.
If the shell option nocasematch
(see the description of shopt
in 4.3.2 The Shopt Builtin)
is enabled, the match is performed without regard to the case
of alphabetic characters.
Any part of the pattern may be quoted to force the quoted portion
to be matched as a string.
Bracket expressions in regular expressions must be treated carefully,
since normal quoting characters lose their meanings between brackets.
If the pattern is stored in a shell variable, quoting the variable
expansion forces the entire pattern to be matched as a string.
Substrings matched by parenthesized subexpressions within the regular
expression are saved in the array variable BASH_REMATCH
.
The element of BASH_REMATCH
with index 0 is the portion of the string
matching the entire regular expression.
The element of BASH_REMATCH
with index n is the portion of the
string matching the nth parenthesized subexpression.
For example, the following will match a line
(stored in the shell variable line)
if there is a sequence of characters in the value consisting of
any number, including zero, of
space characters, zero or one instances of `a', then a `b':
| [[ $line =~ [[:space:]]*(a)?b ]]
|
That means values like `aab' and ` aaaaaab' will match, as
will a line containing a `b' anywhere in its value.
Storing the regular expression in a shell variable is often a useful
way to avoid problems with quoting characters that are special to the
shell.
It is sometimes difficult to specify a regular expression literally
without using quotes, or to keep track of the quoting used by regular
expressions while paying attention to the shell's quote removal.
Using a shell variable to store the pattern decreases these problems.
For example, the following is equivalent to the above:
| pattern='[[:space:]]*(a)?b'
[[ $line =~ $pattern ]]
|
If you want to match a character that's special to the regular expression
grammar, it has to be quoted to remove its special meaning.
This means that in the pattern `xxx.txt', the `.' matches any
character in the string (its usual regular expression meaning), but in the
pattern `"xxx.txt"' it can only match a literal `.'.
Shell programmers should take special care with backslashes, since backslashes
are used both by the shell and regular expressions to remove the special
meaning from the following character.
The following two sets of commands are not equivalent:
| pattern='\.'
[[ . =~ $pattern ]]
[[ . =~ \. ]]
[[ . =~ "$pattern" ]]
[[ . =~ '\.' ]]
|
The first two matches will succeed, but the second two will not, because
in the second two the backslash will be part of the pattern to be matched.
In the first two examples, the backslash removes the special meaning from
`.', so the literal `.' matches.
If the string in the first examples were anything other than `.', say
`a', the pattern would not match, because the quoted `.' in the
pattern loses its special meaning of matching any single character.
Expressions may be combined using the following operators, listed
in decreasing order of precedence:
( expression )
- Returns the value of expression.
This may be used to override the normal precedence of operators.
! expression
- True if expression is false.
expression1 && expression2
- True if both expression1 and expression2 are true.
expression1 || expression2
- True if either expression1 or expression2 is true.
The &&
and ||
operators do not evaluate expression2 if the
value of expression1 is sufficient to determine the return
value of the entire conditional expression.
3.2.4.3 Grouping Commands
Bash provides two ways to group a list of commands to be executed
as a unit. When commands are grouped, redirections may be applied
to the entire command list. For example, the output of all the
commands in the list may be redirected to a single stream.
()
Placing a list of commands between parentheses causes a subshell
environment to be created (see section 3.7.3 Command Execution Environment), and each
of the commands in list to be executed in that subshell. Since the
list is executed in a subshell, variable assignments do not remain in
effect after the subshell completes.
{}
-
Placing a list of commands between curly braces causes the list to
be executed in the current shell context. No subshell is created.
The semicolon (or newline) following list is required.
In addition to the creation of a subshell, there is a subtle difference
between these two constructs due to historical reasons. The braces
are reserved words
, so they must be separated from the list
by blank
s or other shell metacharacters.
The parentheses are operators
, and are
recognized as separate tokens by the shell even if they are not separated
from the list by whitespace.
The exit status of both of these constructs is the exit status of
list.
3.2.5 Coprocesses
A coprocess
is a shell command preceded by the coproc
reserved word.
A coprocess is executed asynchronously in a subshell, as if the command
had been terminated with the `&' control operator, with a two-way pipe
established between the executing shell and the coprocess.
The format for a coprocess is:
| coproc [NAME] command [redirections]
|
This creates a coprocess named NAME.
If NAME is not supplied, the default name is COPROC.
NAME must not be supplied if command is a simple
command (see section 3.2.1 Simple Commands); otherwise, it is interpreted as
the first word of the simple command.
When the coprocess is executed, the shell creates an array variable
(see section 6.7 Arrays)
named NAME
in the context of the executing shell.
The standard output of command
is connected via a pipe to a file descriptor in the executing shell,
and that file descriptor is assigned to NAME
[0].
The standard input of command
is connected via a pipe to a file descriptor in the executing shell,
and that file descriptor is assigned to NAME
[1].
This pipe is established before any redirections specified by the
command (see section 3.6 Redirections).
The file descriptors can be utilized as arguments to shell commands
and redirections using standard word expansions.
The file descriptors are not available in subshells.
The process ID of the shell spawned to execute the coprocess is
available as the value of the variable NAME
_PID.
The wait
builtin command may be used to wait for the coprocess to terminate.
Since the coprocess is created as an asynchronous command,
the coproc
command always returns success.
The return status of a coprocess is the exit status of command.
3.2.6 GNU Parallel
There are ways to run commands in parallel that are not built into Bash.
GNU Parallel is a tool to do just that.
GNU Parallel, as its name suggests, can be used to build and run commands
in parallel. You may run the same command with different arguments, whether
they are filenames, usernames, hostnames, or lines read from files. GNU
Parallel provides shorthand references to many of the most common operations
(input lines, various portions of the input line, different ways to specify
the input source, and so on). Parallel can replace xargs
or feed
commands from its input sources to several different instances of Bash.
For a complete description, refer to the GNU Parallel documentation. A few
examples should provide a brief introduction to its use.
For example, it is easy to replace xargs
to gzip all html files in the
current directory and its subdirectories:
| find . -type f -name '*.html' -print | parallel gzip
|
If you need to protect special characters such as newlines in file names,
use find's `-print0' option and parallel's `-0' option.
You can use Parallel to move files from the current directory when the
number of files is too large to process with one mv
invocation:
| ls | parallel mv {} destdir
|
As you can see, the {} is replaced with each line read from standard input.
While using ls
will work in most instances, it is not sufficient to
deal with all filenames.
If you need to accommodate special characters in filenames, you can use
| find . -depth 1 \! -name '.*' -print0 | parallel -0 mv {} destdir
|
as alluded to above.
This will run as many mv
commands as there are files in the current
directory.
You can emulate a parallel xargs
by adding the `-X' option:
| find . -depth 1 \! -name '.*' -print0 | parallel -0 -X mv {} destdir
|
GNU Parallel can replace certain common idioms that operate on lines read
from a file (in this case, filenames listed one per line):
| while IFS= read -r x; do
do-something1 "$x" "config-$x"
do-something2 < "$x"
done < file | process-output
|
with a more compact syntax reminiscent of lambdas:
| cat list | parallel "do-something1 {} config-{} ; do-something2 < {}" | process-output
|
Parallel provides a built-in mechanism to remove filename extensions, which
lends itself to batch file transformations or renaming:
| ls *.gz | parallel -j+0 "zcat {} | bzip2 >{.}.bz2 && rm {}"
|
This will recompress all files in the current directory with names ending
in .gz using bzip2, running one job per CPU (-j+0) in parallel.
(We use ls
for brevity here; using find
as above is more
robust in the face of filenames containing unexpected characters.)
Parallel can take arguments from the command line; the above can also be
written as
| parallel "zcat {} | bzip2 >{.}.bz2 && rm {}" ::: *.gz
|
If a command generates output, you may want to preserve the input order in
the output. For instance, the following command
| { echo foss.org.my ; echo debian.org; echo freenetproject.org; } | parallel traceroute
|
will display as output the traceroute invocation that finishes first.
Adding the `-k' option
| { echo foss.org.my ; echo debian.org; echo freenetproject.org; } | parallel -k traceroute
|
will ensure that the output of traceroute foss.org.my
is displayed first.
Finally, Parallel can be used to run a sequence of shell commands in parallel,
similar to `cat file | bash'.
It is not uncommon to take a list of filenames, create a series of shell
commands to operate on them, and feed that list of commnds to a shell.
Parallel can speed this up. Assuming that `file' contains a list of
shell commands, one per line,
will evaluate the commands using the shell (since no explicit command is
supplied as an argument), in blocks of ten shell jobs at a time.
3.3 Shell Functions
Shell functions are a way to group commands for later execution
using a single name for the group. They are executed just like
a "regular" command.
When the name of a shell function is used as a simple command name,
the list of commands associated with that function name is executed.
Shell functions are executed in the current
shell context; no new process is created to interpret them.
Functions are declared using this syntax:
| name () compound-command [ redirections ]
|
or
| function name [()] compound-command [ redirections ]
|
This defines a shell function named name. The reserved
word function
is optional.
If the function
reserved
word is supplied, the parentheses are optional.
The body of the function is the compound command
compound-command (see section 3.2.4 Compound Commands).
That command is usually a list enclosed between { and }, but
may be any compound command listed above.
compound-command is executed whenever name is specified as the
name of a command.
When the shell is in POSIX mode (see section 6.11 Bash POSIX Mode),
name may not be the same as one of the special builtins
(see section 4.4 Special Builtins).
Any redirections (see section 3.6 Redirections) associated with the shell function
are performed when the function is executed.
A function definition may be deleted using the `-f' option to the
unset
builtin (see section 4.1 Bourne Shell Builtins).
The exit status of a function definition is zero unless a syntax error
occurs or a readonly function with the same name already exists.
When executed, the exit status of a function is the exit status of the
last command executed in the body.
Note that for historical reasons, in the most common usage the curly braces
that surround the body of the function must be separated from the body by
blank
s or newlines.
This is because the braces are reserved words and are only recognized
as such when they are separated from the command list
by whitespace or another shell metacharacter.
Also, when using the braces, the list must be terminated by a semicolon,
a `&', or a newline.
When a function is executed, the arguments to the
function become the positional parameters
during its execution (see section 3.4.1 Positional Parameters).
The special parameter `#' that expands to the number of
positional parameters is updated to reflect the change.
Special parameter 0
is unchanged.
The first element of the FUNCNAME
variable is set to the
name of the function while the function is executing.
All other aspects of the shell execution
environment are identical between a function and its caller
with these exceptions:
the DEBUG
and RETURN
traps
are not inherited unless the function has been given the
trace
attribute using the declare
builtin or
the -o functrace
option has been enabled with
the set
builtin,
(in which case all functions inherit the DEBUG
and RETURN
traps),
and the ERR
trap is not inherited unless the -o errtrace
shell option has been enabled.
See section 4.1 Bourne Shell Builtins, for the description of the
trap
builtin.
The FUNCNEST
variable, if set to a numeric value greater
than 0, defines a maximum function nesting level. Function
invocations that exceed the limit cause the entire command to
abort.
If the builtin command return
is executed in a function, the function completes and
execution resumes with the next command after the function
call.
Any command associated with the RETURN
trap is executed
before execution resumes.
When a function completes, the values of the
positional parameters and the special parameter `#'
are restored to the values they had prior to the function's
execution. If a numeric argument is given to return
,
that is the function's return status; otherwise the function's
return status is the exit status of the last command executed
before the return
.
Variables local to the function may be declared with the
local
builtin. These variables are visible only to
the function and the commands it invokes.
Function names and definitions may be listed with the
`-f' option to the declare
(typeset
)
builtin command (see section 4.2 Bash Builtin Commands).
The `-F' option to declare
or typeset
will list the function names only
(and optionally the source file and line number, if the extdebug
shell option is enabled).
Functions may be exported so that subshells
automatically have them defined with the
`-f' option to the export
builtin
(see section 4.1 Bourne Shell Builtins).
Note that shell functions and variables with the same name may result
in multiple identically-named entries in the environment passed to the
shell's children.
Care should be taken in cases where this may cause a problem.
Functions may be recursive.
The FUNCNEST
variable may be used to limit the depth of the
function call stack and restrict the number of function invocations.
By default, no limit is placed on the number of recursive calls.
3.4 Shell Parameters
A parameter is an entity that stores values.
It can be a name
, a number, or one of the special characters
listed below.
A variable is a parameter denoted by a name
.
A variable has a value and zero or more attributes.
Attributes are assigned using the declare
builtin command
(see the description of the declare
builtin in 4.2 Bash Builtin Commands).
A parameter is set if it has been assigned a value. The null string is
a valid value. Once a variable is set, it may be unset only by using
the unset
builtin command.
A variable may be assigned to by a statement of the form
If value
is not given, the variable is assigned the null string. All
values undergo tilde expansion, parameter and variable expansion,
command substitution, arithmetic expansion, and quote
removal (detailed below). If the variable has its integer
attribute set, then value
is evaluated as an arithmetic expression even if the $((...))
expansion is not used (see section 3.5.5 Arithmetic Expansion).
Word splitting is not performed, with the exception
of "$@"
as explained below.
Filename expansion is not performed.
Assignment statements may also appear as arguments to the
alias
,
declare
, typeset
, export
, readonly
,
and local
builtin commands.
When in POSIX mode (see section 6.11 Bash POSIX Mode), these builtins may appear
in a command after one or more instances of the command
builtin
and retain these assignment statement properties.
In the context where an assignment statement is assigning a value
to a shell variable or array index (see section 6.7 Arrays), the `+='
operator can be used to
append to or add to the variable's previous value.
When `+=' is applied to a variable for which the integer attribute
has been set, value is evaluated as an arithmetic expression and
added to the variable's current value, which is also evaluated.
When `+=' is applied to an array variable using compound assignment
(see section 6.7 Arrays), the
variable's value is not unset (as it is when using `='), and new
values are appended to the array beginning at one greater than the array's
maximum index (for indexed arrays), or added as additional key-value pairs
in an associative array.
When applied to a string-valued variable, value is expanded and
appended to the variable's value.
A variable can be assigned the nameref attribute using the
`-n' option to the \fBdeclare\fP or \fBlocal\fP builtin commands
(see section 4.2 Bash Builtin Commands)
to create a nameref, or a reference to another variable.
This allows variables to be manipulated indirectly.
Whenever the nameref variable is referenced or assigned to, the operation
is actually performed on the variable specified by the nameref variable's
value.
A nameref is commonly used within shell functions to refer to a variable
whose name is passed as an argument to the function.
For instance, if a variable name is passed to a shell function as its first
argument, running
inside the function creates a nameref variable ref whose value is
the variable name passed as the first argument.
References and assignments to ref are treated as references and
assignments to the variable whose name was passed as $1
.
If the control variable in a for
loop has the nameref attribute,
the list of words can be a list of shell variables, and a name reference
will be established for each word in the list, in turn, when the loop is
executed.
Array variables cannot be given the `-n' attribute.
However, nameref variables can reference array variables and subscripted
array variables.
Namerefs can be unset using the `-n' option to the unset
builtin
(see section 4.1 Bourne Shell Builtins).
Otherwise, if unset
is executed with the name of a nameref variable
as an argument, the variable referenced by the nameref variable will be unset.
3.4.1 Positional Parameters
A positional parameter is a parameter denoted by one or more
digits, other than the single digit 0
. Positional parameters are
assigned from the shell's arguments when it is invoked,
and may be reassigned using the set
builtin command.
Positional parameter N
may be referenced as ${N}
, or
as $N
when N
consists of a single digit.
Positional parameters may not be assigned to with assignment statements.
The set
and shift
builtins are used to set and
unset them (see section 4. Shell Builtin Commands).
The positional parameters are
temporarily replaced when a shell function is executed
(see section 3.3 Shell Functions).
When a positional parameter consisting of more than a single
digit is expanded, it must be enclosed in braces.
3.4.2 Special Parameters
The shell treats several parameters specially. These parameters may
only be referenced; assignment to them is not allowed.
*
-
($*) Expands to the positional parameters, starting from one.
When the expansion is not within double quotes, each positional parameter
expands to a separate word.
In contexts where it is performed, those words
are subject to further word splitting and pathname expansion.
When the expansion occurs within double quotes, it expands to a single word
with the value of each parameter separated by the first character
of the
IFS
special variable. That is, "$*"
is equivalent
to "$1c$2c..."
, where c
is the first character of the value of the IFS
variable.
If IFS
is unset, the parameters are separated by spaces.
If IFS
is null, the parameters are joined without intervening
separators.
@
-
($@) Expands to the positional parameters, starting from one. When the
expansion occurs within double quotes, each parameter expands to a
separate word. That is,
"$@"
is equivalent to
"$1" "$2" ...
.
If the double-quoted expansion occurs within a word, the expansion of
the first parameter is joined with the beginning part of the original
word, and the expansion of the last parameter is joined with the last
part of the original word.
When there are no positional parameters, "$@"
and
$@
expand to nothing (i.e., they are removed).
#
-
($#) Expands to the number of positional parameters in decimal.
?
-
($?) Expands to the exit status of the most recently executed foreground
pipeline.
-
-
($-, a hyphen.) Expands to the current option flags as specified upon
invocation, by the
set
builtin command, or those set by the shell itself
(such as the `-i' option).
$
-
($$) Expands to the process ID of the shell. In a
()
subshell, it
expands to the process ID of the invoking shell, not the subshell.
!
-
($!) Expands to the process ID of the job most recently placed into the
background, whether executed as an asynchronous command or using
the
bg
builtin (see section 7.2 Job Control Builtins).
0
-
($0) Expands to the name of the shell or shell script. This is set at
shell initialization. If Bash is invoked with a file of commands
(see section 3.8 Shell Scripts),
$0
is set to the name of that file.
If Bash is started with the `-c' option (see section 6.1 Invoking Bash),
then $0
is set to the first argument after the string to be
executed, if one is present. Otherwise, it is set
to the filename used to invoke Bash, as given by argument zero.
_
-
($_, an underscore.)
At shell startup, set to the absolute pathname used to invoke the
shell or shell script being executed as passed in the environment
or argument list.
Subsequently, expands to the last argument to the previous command,
after expansion.
Also set to the full pathname used to invoke each command executed
and placed in the environment exported to that command.
When checking mail, this parameter holds the name of the mail file.
3.5 Shell Expansions
Expansion is performed on the command line after it has been split into
token
s. There are seven kinds of expansion performed:
- brace expansion
- tilde expansion
- parameter and variable expansion
- command substitution
- arithmetic expansion
- word splitting
- filename expansion
The order of expansions is:
brace expansion;
tilde expansion, parameter and variable expansion, arithmetic expansion,
and command substitution (done in a left-to-right fashion);
word splitting;
and filename expansion.
On systems that can support it, there is an additional expansion
available: process substitution.
This is performed at the
same time as tilde, parameter, variable, and arithmetic expansion and
command substitution.
Only brace expansion, word splitting, and filename expansion
can change the number of words of the expansion; other expansions
expand a single word to a single word.
The only exceptions to this are the expansions of
"$@"
(see section 3.4.2 Special Parameters) and "${name[@]}"
(see section 6.7 Arrays).
After all expansions, quote removal
(see section 3.5.9 Quote Removal)
is performed.
3.5.1 Brace Expansion
Brace expansion is a mechanism by which arbitrary strings may be generated.
This mechanism is similar to
filename expansion (see section 3.5.8 Filename Expansion),
but the filenames generated need not exist.
Patterns to be brace expanded take the form of an optional preamble,
followed by either a series of comma-separated strings or a sequence expression
between a pair of braces,
followed by an optional postscript.
The preamble is prefixed to each string contained within the braces, and
the postscript is then appended to each resulting string, expanding left
to right.
Brace expansions may be nested.
The results of each expanded string are not sorted; left to right order
is preserved.
For example,
| bash$ echo a{d,c,b}e
ade ace abe
|
A sequence expression takes the form {x..y[..incr]}
,
where x and y are either integers or single characters,
and incr, an optional increment, is an integer.
When integers are supplied, the expression expands to each number between
x and y, inclusive.
Supplied integers may be prefixed with `0' to force each term to have the
same width.
When either x or y begins with a zero, the shell
attempts to force all generated terms to contain the same number of digits,
zero-padding where necessary.
When characters are supplied, the expression expands to each character
lexicographically between x and y, inclusive,
using the default C locale.
Note that both x and y must be of the same type.
When the increment is supplied, it is used as the difference between
each term. The default increment is 1 or -1 as appropriate.
Brace expansion is performed before any other expansions,
and any characters special to other expansions are preserved
in the result. It is strictly textual. Bash
does not apply any syntactic interpretation to the context of the
expansion or the text between the braces.
To avoid conflicts with parameter expansion, the string `${'
is not considered eligible for brace expansion.
A correctly-formed brace expansion must contain unquoted opening
and closing braces, and at least one unquoted comma or a valid
sequence expression.
Any incorrectly formed brace expansion is left unchanged.
A { or `,' may be quoted with a backslash to prevent its
being considered part of a brace expression.
To avoid conflicts with parameter expansion, the string `${'
is not considered eligible for brace expansion.
This construct is typically used as shorthand when the common
prefix of the strings to be generated is longer than in the
above example:
| mkdir /usr/local/src/bash/{old,new,dist,bugs}
|
or
| chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
|
3.5.2 Tilde Expansion
If a word begins with an unquoted tilde character (`~'), all of the
characters up to the first unquoted slash (or all characters,
if there is no unquoted slash) are considered a tilde-prefix.
If none of the characters in the tilde-prefix are quoted, the
characters in the tilde-prefix following the tilde are treated as a
possible login name.
If this login name is the null string, the tilde is replaced with the
value of the HOME
shell variable.
If HOME
is unset, the home directory of the user executing the
shell is substituted instead.
Otherwise, the tilde-prefix is replaced with the home directory
associated with the specified login name.
If the tilde-prefix is `~+', the value of
the shell variable PWD
replaces the tilde-prefix.
If the tilde-prefix is `~-', the value of the shell variable
OLDPWD
, if it is set, is substituted.
If the characters following the tilde in the tilde-prefix consist of a
number N, optionally prefixed by a `+' or a `-',
the tilde-prefix is replaced with the
corresponding element from the directory stack, as it would be displayed
by the dirs
builtin invoked with the characters following tilde
in the tilde-prefix as an argument (see section 6.8 The Directory Stack).
If the tilde-prefix, sans the tilde, consists of a number without a
leading `+' or `-', `+' is assumed.
If the login name is invalid, or the tilde expansion fails, the word is
left unchanged.
Each variable assignment is checked for unquoted tilde-prefixes immediately
following a `:' or the first `='.
In these cases, tilde expansion is also performed.
Consequently, one may use filenames with tildes in assignments to
PATH
, MAILPATH
, and CDPATH
,
and the shell assigns the expanded value.
The following table shows how Bash treats unquoted tilde-prefixes:
~
- The value of
$HOME
~/foo
- `$HOME/foo'
~fred/foo
- The subdirectory
foo
of the home directory of the user
fred
~+/foo
- `$PWD/foo'
~-/foo
- `${OLDPWD-'~-'}/foo'
~N
- The string that would be displayed by `dirs +N'
~+N
- The string that would be displayed by `dirs +N'
~-N
- The string that would be displayed by `dirs -N'
3.5.3 Shell Parameter Expansion
The `$' character introduces parameter expansion,
command substitution, or arithmetic expansion. The parameter name
or symbol to be expanded may be enclosed in braces, which
are optional but serve to protect the variable to be expanded from
characters immediately following it which could be
interpreted as part of the name.
When braces are used, the matching ending brace is the first `}'
not escaped by a backslash or within a quoted string, and not within an
embedded arithmetic expansion, command substitution, or parameter
expansion.
The basic form of parameter expansion is ${parameter}.
The value of parameter is substituted.
The parameter is a shell parameter as described above
(see section 3.4 Shell Parameters) or an array reference (see section 6.7 Arrays).
The braces are required when parameter
is a positional parameter with more than one digit,
or when parameter is followed by a character that is not to be
interpreted as part of its name.
If the first character of parameter is an exclamation point (!),
it introduces a level of variable indirection.
Bash uses the value of the variable formed from the rest of
parameter as the name of the variable; this variable is then
expanded and that value is used in the rest of the substitution, rather
than the value of parameter itself.
This is known as indirect expansion
.
The exceptions to this are the expansions of ${!prefix*}
and ${!name[@]}
described below.
The exclamation point must immediately follow the left brace in order to
introduce indirection.
In each of the cases below, word is subject to tilde expansion,
parameter expansion, command substitution, and arithmetic expansion.
When not performing substring expansion, using the form described
below (e.g., `:-'), Bash tests for a parameter that is unset or null.
Omitting the colon results in a test only for a parameter that is unset.
Put another way, if the colon is included,
the operator tests for both parameter's existence and that its value
is not null; if the colon is omitted, the operator tests only for existence.
${parameter:-word}
- If parameter is unset or null, the expansion of
word is substituted. Otherwise, the value of
parameter is substituted.
${parameter:=word}
- If parameter
is unset or null, the expansion of word
is assigned to parameter.
The value of parameter is then substituted.
Positional parameters and special parameters may not be assigned to
in this way.
${parameter:?word}
- If parameter
is null or unset, the expansion of word (or a message
to that effect if word
is not present) is written to the standard error and the shell, if it
is not interactive, exits. Otherwise, the value of parameter is
substituted.
${parameter:+word}
- If parameter
is null or unset, nothing is substituted, otherwise the expansion of
word is substituted.
${parameter:offset}
${parameter:offset:length}
- This is referred to as Substring Expansion.
It expands to up to length characters of the value of parameter
starting at the character specified by offset.
If parameter is `@', an indexed array subscripted by
`@' or `*', or an associative array name, the results differ as
described below.
If length is omitted, it expands to the substring of the value of
parameter starting at the character specified by offset
and extending to the end of the value.
length and offset are arithmetic expressions
(see section 6.5 Shell Arithmetic).
If offset evaluates to a number less than zero, the value
is used as an offset in characters
from the end of the value of parameter.
If length evaluates to a number less than zero,
it is interpreted as an offset in characters
from the end of the value of parameter rather than
a number of characters, and the expansion is the characters between
offset and that result.
Note that a negative offset must be separated from the colon by at least
one space to avoid being confused with the `:-' expansion.
Here are some examples illustrating substring expansion on parameters and
subscripted arrays:
@verbatim
$ string=01234567890abcdefgh
$ echo ${string:7}
7890abcdefgh
$ echo ${string:7:0}
$ echo ${string:7:2}
78
$ echo ${string:7:-2}
7890abcdef
$ echo ${string: -7}
bcdefgh
$ echo ${string: -7:0}
$ echo ${string: -7:2}
bc
$ echo ${string: -7:-2}
bcdef
$ set -- 01234567890abcdefgh
$ echo ${1:7}
7890abcdefgh
$ echo ${1:7:0}
$ echo ${1:7:2}
78
$ echo ${1:7:-2}
7890abcdef
$ echo ${1: -7}
bcdefgh
$ echo ${1: -7:0}
$ echo ${1: -7:2}
bc
$ echo ${1: -7:-2}
bcdef
$ array[0]=01234567890abcdefgh
$ echo ${array[0]:7}
7890abcdefgh
$ echo ${array[0]:7:0}
$ echo ${array[0]:7:2}
78
$ echo ${array[0]:7:-2}
7890abcdef
$ echo ${array[0]: -7}
bcdefgh
$ echo ${array[0]: -7:0}
$ echo ${array[0]: -7:2}
bc
$ echo ${array[0]: -7:-2}
bcdef
If parameter is `@', the result is length positional
parameters beginning at offset.
A negative offset is taken relative to one greater than the greatest
positional parameter, so an offset of -1 evaluates to the last positional
parameter.
It is an expansion error if length evaluates to a number less than zero.
The following examples illustrate substring expansion using positional
parameters:
@verbatim
$ set -- 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
$ echo ${7}
7 8 9 0 a b c d e f g h
$ echo ${7:0}
$ echo ${7:2}
7 8
$ echo ${7:-2}
bash: -2: substring expression < 0
$ echo ${ -7:2}
b c
$ echo ${0}
./bash 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
$ echo ${0:2}
./bash 1
$ echo ${ -7:0}
If parameter is an indexed array name subscripted
by `@' or `*', the result is the length
members of the array beginning with ${parameter[offset]}
.
A negative offset is taken relative to one greater than the maximum
index of the specified array.
It is an expansion error if length evaluates to a number less than zero.
These examples show how you can use substring expansion with indexed
arrays:
@verbatim
$ array=(0 1 2 3 4 5 6 7 8 9 0 a b c d e f g h)
$ echo ${array[@]:7}
7 8 9 0 a b c d e f g h
$ echo ${array[@]:7:2}
7 8
$ echo ${array[@]: -7:2}
b c
$ echo ${array[@]: -7:-2}
bash: -2: substring expression < 0
$ echo ${array[@]:0}
0 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
$ echo ${array[@]:0:2}
0 1
$ echo ${array[@]: -7:0}
Substring expansion applied to an associative array produces undefined
results.
Substring indexing is zero-based unless the positional parameters
are used, in which case the indexing starts at 1 by default.
If offset is 0, and the positional parameters are used, $@
is
prefixed to the list.
${!prefix*}
${!prefix@}
- Expands to the names of variables whose names begin with prefix,
separated by the first character of the
IFS
special variable.
When `@' is used and the expansion appears within double quotes, each
variable name expands to a separate word.
${!name[@]}
${!name[*]}
- If name is an array variable, expands to the list of array indices
(keys) assigned in name.
If name is not an array, expands to 0 if name is set and null
otherwise.
When `@' is used and the expansion appears within double quotes, each
key expands to a separate word.
${#parameter}
- The length in characters of the expanded value of parameter is
substituted.
If parameter is `*' or `@', the value substituted
is the number of positional parameters.
If parameter is an array name subscripted by `*' or `@',
the value substituted is the number of elements in the array.
If parameter
is an indexed array name subscripted by a negative number, that number is
interpreted as relative to one greater than the maximum index of
parameter, so negative indices count back from the end of the
array, and an index of -1 references the last element.
${parameter#word}
${parameter##word}
- The word
is expanded to produce a pattern just as in filename
expansion (see section 3.5.8 Filename Expansion). If the pattern matches
the beginning of the expanded value of parameter,
then the result of the expansion is the expanded value of parameter
with the shortest matching pattern (the `#' case) or the
longest matching pattern (the `##' case) deleted.
If parameter is `@' or `*',
the pattern removal operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If parameter is an array variable subscripted with
`@' or `*',
the pattern removal operation is applied to each member of the
array in turn, and the expansion is the resultant list.
${parameter%word}
${parameter%%word}
- The word is expanded to produce a pattern just as in
filename expansion.
If the pattern matches a trailing portion of the expanded value of
parameter, then the result of the expansion is the value of
parameter with the shortest matching pattern (the `%' case)
or the longest matching pattern (the `%%' case) deleted.
If parameter is `@' or `*',
the pattern removal operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If parameter
is an array variable subscripted with `@' or `*',
the pattern removal operation is applied to each member of the
array in turn, and the expansion is the resultant list.
${parameter/pattern/string}
The pattern is expanded to produce a pattern just as in
filename expansion.
Parameter is expanded and the longest match of pattern
against its value is replaced with string.
If pattern begins with `/', all matches of pattern are
replaced with string. Normally only the first match is replaced.
If pattern begins with `#', it must match at the beginning
of the expanded value of parameter.
If pattern begins with `%', it must match at the end
of the expanded value of parameter.
If string is null, matches of pattern are deleted
and the /
following pattern may be omitted.
If parameter is `@' or `*',
the substitution operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If parameter
is an array variable subscripted with `@' or `*',
the substitution operation is applied to each member of the
array in turn, and the expansion is the resultant list.
${parameter^pattern}
${parameter^^pattern}
${parameter,pattern}
${parameter,,pattern}
- This expansion modifies the case of alphabetic characters in parameter.
The pattern is expanded to produce a pattern just as in
filename expansion.
Each character in the expanded value of parameter is tested against
pattern, and, if it matches the pattern, its case is converted.
The pattern should not attempt to match more than one character.
The `^' operator converts lowercase letters matching pattern
to uppercase; the `,' operator converts matching uppercase letters
to lowercase.
The `^^' and `,,' expansions convert each matched character in the
expanded value; the `^' and `,' expansions match and convert only
the first character in the expanded value.
If pattern is omitted, it is treated like a `?', which matches
every character.
If parameter is `@' or `*',
the case modification operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If parameter
is an array variable subscripted with `@' or `*',
the case modification operation is applied to each member of the
array in turn, and the expansion is the resultant list.
3.5.4 Command Substitution
Command substitution allows the output of a command to replace
the command itself.
Command substitution occurs when a command is enclosed as follows:
or
Bash performs the expansion by executing command and
replacing the command substitution with the standard output of the
command, with any trailing newlines deleted.
Embedded newlines are not deleted, but they may be removed during
word splitting.
The command substitution $(cat file)
can be
replaced by the equivalent but faster $(< file)
.
When the old-style backquote form of substitution is used,
backslash retains its literal meaning except when followed by
`$', ``', or `\'.
The first backquote not preceded by a backslash terminates the
command substitution.
When using the $(command)
form, all characters between
the parentheses make up the command; none are treated specially.
Command substitutions may be nested. To nest when using the backquoted
form, escape the inner backquotes with backslashes.
If the substitution appears within double quotes, word splitting and
filename expansion are not performed on the results.
3.5.5 Arithmetic Expansion
Arithmetic expansion allows the evaluation of an arithmetic expression
and the substitution of the result. The format for arithmetic expansion is:
The expression is treated as if it were within double quotes, but
a double quote inside the parentheses is not treated specially.
All tokens in the expression undergo parameter and variable expansion,
command substitution, and quote removal.
The result is treated as the arithmetic expression to be evaluated.
Arithmetic expansions may be nested.
The evaluation is performed according to the rules listed below
(see section 6.5 Shell Arithmetic).
If the expression is invalid, Bash prints a message indicating
failure to the standard error and no substitution occurs.
3.5.6 Process Substitution
Process substitution is supported on systems that support named
pipes (FIFOs) or the `/dev/fd' method of naming open files.
It takes the form of
or
The process list is run with its input or output connected to a
FIFO or some file in `/dev/fd'. The name of this file is
passed as an argument to the current command as the result of the
expansion. If the >(list)
form is used, writing to
the file will provide input for list. If the
<(list)
form is used, the file passed as an
argument should be read to obtain the output of list.
Note that no space may appear between the <
or >
and the left parenthesis, otherwise the construct would be interpreted
as a redirection.
When available, process substitution is performed simultaneously with
parameter and variable expansion, command substitution, and arithmetic
expansion.
3.5.7 Word Splitting
The shell scans the results of parameter expansion, command substitution,
and arithmetic expansion that did not occur within double quotes for
word splitting.
The shell treats each character of $IFS
as a delimiter, and splits
the results of the other expansions into words using these characters
as field terminators.
If IFS
is unset, or its value is exactly <space><tab><newline>
,
the default, then sequences of
<space>
, <tab>
, and <newline>
at the beginning and end of the results of the previous
expansions are ignored, and any sequence of IFS
characters not at the beginning or end serves to delimit words.
If IFS
has a value other than the default, then sequences of
the whitespace characters space
and tab
are ignored at the beginning and end of the
word, as long as the whitespace character is in the
value of IFS
(an IFS
whitespace character).
Any character in IFS
that is not IFS
whitespace, along with any adjacent IFS
whitespace characters, delimits a field. A sequence of IFS
whitespace characters is also treated as a delimiter.
If the value of IFS
is null, no word splitting occurs.
Explicit null arguments (""
or "
) are retained.
Unquoted implicit null arguments, resulting from the expansion of
parameters that have no values, are removed.
If a parameter with no value is expanded within double quotes, a
null argument results and is retained.
Note that if no expansion occurs, no splitting
is performed.
3.5.8 Filename Expansion
After word splitting, unless the `-f' option has been set
(see section 4.3.1 The Set Builtin), Bash scans each word for the characters
`*', `?', and `['.
If one of these characters appears, then the word is
regarded as a pattern,
and replaced with an alphabetically sorted list of
filenames matching the pattern (see section 3.5.8.1 Pattern Matching).
If no matching filenames are found,
and the shell option nullglob
is disabled, the word is left
unchanged.
If the nullglob
option is set, and no matches are found, the word
is removed.
If the failglob
shell option is set, and no matches are found,
an error message is printed and the command is not executed.
If the shell option nocaseglob
is enabled, the match is performed
without regard to the case of alphabetic characters.
When a pattern is used for filename expansion, the character `.'
at the start of a filename or immediately following a slash
must be matched explicitly, unless the shell option dotglob
is set.
When matching a filename, the slash character must always be
matched explicitly.
In other cases, the `.' character is not treated specially.
See the description of shopt
in 4.3.2 The Shopt Builtin,
for a description of the nocaseglob
, nullglob
,
failglob
, and dotglob
options.
The GLOBIGNORE
shell variable may be used to restrict the set of filenames matching a
pattern. If GLOBIGNORE
is set, each matching filename that also matches one of the patterns in
GLOBIGNORE
is removed from the list of matches. The filenames
`.' and `..'
are always ignored when GLOBIGNORE
is set and not null.
However, setting GLOBIGNORE
to a non-null value has the effect of
enabling the dotglob
shell option, so all other filenames beginning with a
`.' will match.
To get the old behavior of ignoring filenames beginning with a
`.', make `.*' one of the patterns in GLOBIGNORE
.
The dotglob
option is disabled when GLOBIGNORE
is unset.
3.5.8.1 Pattern Matching
Any character that appears in a pattern, other than the special pattern
characters described below, matches itself.
The NUL character may not occur in a pattern.
A backslash escapes the following character; the
escaping backslash is discarded when matching.
The special pattern characters must be quoted if they are to be matched
literally.
The special pattern characters have the following meanings:
*
- Matches any string, including the null string.
When the
globstar
shell option is enabled, and `*' is used in
a filename expansion context, two adjacent `*'s used as a single
pattern will match all files and zero or more directories and
subdirectories.
If followed by a `/', two adjacent `*'s will match only
directories and subdirectories.
?
- Matches any single character.
[...]
- Matches any one of the enclosed characters. A pair of characters
separated by a hyphen denotes a range expression;
any character that falls between those two characters, inclusive,
using the current locale's collating sequence and character set,
is matched. If the first character following the
`[' is a `!' or a `^'
then any character not enclosed is matched. A `-'
may be matched by including it as the first or last character
in the set. A `]' may be matched by including it as the first
character in the set.
The sorting order of characters in range expressions is determined by
the current locale and the values of the
LC_COLLATE
and LC_ALL
shell variables, if set.
For example, in the default C locale, `[a-dx-z]' is equivalent to
`[abcdxyz]'. Many locales sort characters in dictionary order, and in
these locales `[a-dx-z]' is typically not equivalent to `[abcdxyz]';
it might be equivalent to `[aBbCcDdxXyYz]', for example. To obtain
the traditional interpretation of ranges in bracket expressions, you can
force the use of the C locale by setting the LC_COLLATE
or
LC_ALL
environment variable to the value `C', or enable the
globasciiranges
shell option.
Within `[' and `]', character classes can be specified
using the syntax
[:
class:]
, where class is one of the
following classes defined in the POSIX standard:
| alnum alpha ascii blank cntrl digit graph lower
print punct space upper word xdigit
|
A character class matches any character belonging to that class.
The word
character class matches letters, digits, and the character
`_'.
Within `[' and `]', an equivalence class can be
specified using the syntax [=
c=]
, which
matches all characters with the same collation weight (as defined
by the current locale) as the character c.
Within `[' and `]', the syntax [.
symbol.]
matches the collating symbol symbol.
If the extglob
shell option is enabled using the shopt
builtin, several extended pattern matching operators are recognized.
In the following description, a pattern-list is a list of one
or more patterns separated by a `|'.
Composite patterns may be formed using one or more of the following
sub-patterns:
?(pattern-list)
- Matches zero or one occurrence of the given patterns.
*(pattern-list)
- Matches zero or more occurrences of the given patterns.
+(pattern-list)
- Matches one or more occurrences of the given patterns.
@(pattern-list)
- Matches one of the given patterns.
!(pattern-list)
- Matches anything except one of the given patterns.
3.5.9 Quote Removal
After the preceding expansions, all unquoted occurrences of the
characters `\', `'', and `"' that did not
result from one of the above expansions are removed.
3.6 Redirections
Before a command is executed, its input and output
may be redirected
using a special notation interpreted by the shell.
Redirection allows commands' file handles to be
duplicated, opened, closed,
made to refer to different files,
and can change the files the command reads from and writes to.
Redirection may also be used to modify file handles in the
current shell execution environment. The following redirection
operators may precede or appear anywhere within a
simple command or may follow a command.
Redirections are processed in the order they appear, from
left to right.
Each redirection that may be preceded by a file descriptor number
may instead be preceded by a word of the form {varname}.
In this case, for each redirection operator except
>&- and <&-, the shell will allocate a file descriptor greater
than 10 and assign it to {varname}. If >&- or <&- is preceded
by {varname}, the value of varname defines the file
descriptor to close.
In the following descriptions, if the file descriptor number is
omitted, and the first character of the redirection operator is
`<', the redirection refers to the standard input (file
descriptor 0). If the first character of the redirection operator
is `>', the redirection refers to the standard output (file
descriptor 1).
The word following the redirection operator in the following
descriptions, unless otherwise noted, is subjected to brace expansion,
tilde expansion, parameter expansion, command substitution, arithmetic
expansion, quote removal, filename expansion, and word splitting.
If it expands to more than one word, Bash reports an error.
Note that the order of redirections is significant. For example,
the command
directs both standard output (file descriptor 1) and standard error
(file descriptor 2) to the file dirlist, while the command
directs only the standard output to file dirlist,
because the standard error was made a copy of the standard output
before the standard output was redirected to dirlist.
Bash handles several filenames specially when they are used in
redirections, as described in the following table:
/dev/fd/fd
- If fd is a valid integer, file descriptor fd is duplicated.
/dev/stdin
- File descriptor 0 is duplicated.
/dev/stdout
- File descriptor 1 is duplicated.
/dev/stderr
- File descriptor 2 is duplicated.
/dev/tcp/host/port
- If host is a valid hostname or Internet address, and port
is an integer port number or service name, Bash attempts to open
the corresponding TCP socket.
/dev/udp/host/port
- If host is a valid hostname or Internet address, and port
is an integer port number or service name, Bash attempts to open
the corresponding UDP socket.
A failure to open or create a file causes the redirection to fail.
Redirections using file descriptors greater than 9 should be used with
care, as they may conflict with file descriptors the shell uses
internally.
3.6.1 Redirecting Input
Redirection of input causes the file whose name results from
the expansion of word
to be opened for reading on file descriptor n
,
or the standard input (file descriptor 0) if n
is not specified.
The general format for redirecting input is:
3.6.2 Redirecting Output
Redirection of output causes the file whose name results from
the expansion of word
to be opened for writing on file descriptor n,
or the standard output (file descriptor 1) if n
is not specified. If the file does not exist it is created;
if it does exist it is truncated to zero size.
The general format for redirecting output is:
If the redirection operator is `>', and the noclobber
option to the set
builtin has been enabled, the redirection
will fail if the file whose name results from the expansion of
word exists and is a regular file.
If the redirection operator is `>|', or the redirection operator is
`>' and the noclobber
option is not enabled, the redirection
is attempted even if the file named by word exists.
3.6.3 Appending Redirected Output
Redirection of output in this fashion
causes the file whose name results from
the expansion of word
to be opened for appending on file descriptor n,
or the standard output (file descriptor 1) if n
is not specified. If the file does not exist it is created.
The general format for appending output is:
3.6.4 Redirecting Standard Output and Standard Error
This construct allows both the
standard output (file descriptor 1) and
the standard error output (file descriptor 2)
to be redirected to the file whose name is the
expansion of word.
There are two formats for redirecting standard output and
standard error:
and
Of the two forms, the first is preferred.
This is semantically equivalent to
When using the second form, word may not expand to a number or
`-'. If it does, other redirection operators apply
(see Duplicating File Descriptors below) for compatibility reasons.
3.6.5 Appending Standard Output and Standard Error
This construct allows both the
standard output (file descriptor 1) and
the standard error output (file descriptor 2)
to be appended to the file whose name is the
expansion of word.
The format for appending standard output and standard error is:
This is semantically equivalent to
(see Duplicating File Descriptors below).
3.6.6 Here Documents
This type of redirection instructs the shell to read input from the
current source until a line containing only word
(with no trailing blanks) is seen. All of
the lines read up to that point are then used as the standard
input for a command.
The format of here-documents is:
| <<[-]word
here-document
delimiter
|
No parameter and variable expansion, command substitution,
arithmetic expansion, or filename expansion is performed on
word. If any characters in word are quoted, the
delimiter is the result of quote removal on word,
and the lines in the here-document are not expanded.
If word is unquoted,
all lines of the here-document are subjected to
parameter expansion, command substitution, and arithmetic expansion,
the character sequence \newline
is ignored, and `\'
must be used to quote the characters
`\', `$', and ``'.
If the redirection operator is `<<-',
then all leading tab characters are stripped from input lines and the
line containing delimiter.
This allows here-documents within shell scripts to be indented in a
natural fashion.
3.6.7 Here Strings
A variant of here documents, the format is:
The word undergoes
brace expansion, tilde expansion, parameter and variable expansion,
command substitution, arithmetic expansion, and quote removal.
Pathname expansion and word splitting are not performed.
The result is supplied as a single string to the command on its
standard input.
3.6.8 Duplicating File Descriptors
The redirection operator
is used to duplicate input file descriptors.
If word
expands to one or more digits, the file descriptor denoted by n
is made to be a copy of that file descriptor.
If the digits in word do not specify a file descriptor open for
input, a redirection error occurs.
If word
evaluates to `-', file descriptor n is closed.
If n is not specified, the standard input (file descriptor 0) is used.
The operator
is used similarly to duplicate output file descriptors. If
n is not specified, the standard output (file descriptor 1) is used.
If the digits in word do not specify a file descriptor open for
output, a redirection error occurs.
If word
evaluates to `-', file descriptor n is closed.
As a special case, if n is omitted, and word does not
expand to one or more digits or `-', the standard output and standard
error are redirected as described previously.
3.6.9 Moving File Descriptors
The redirection operator
moves the file descriptor digit to file descriptor n,
or the standard input (file descriptor 0) if n is not specified.
digit is closed after being duplicated to n.
Similarly, the redirection operator
moves the file descriptor digit to file descriptor n,
or the standard output (file descriptor 1) if n is not specified.
3.6.10 Opening File Descriptors for Reading and Writing
The redirection operator
causes the file whose name is the expansion of word
to be opened for both reading and writing on file descriptor
n, or on file descriptor 0 if n
is not specified. If the file does not exist, it is created.
3.7 Executing Commands
3.7.1 Simple Command Expansion
When a simple command is executed, the shell performs the following
expansions, assignments, and redirections, from left to right.
-
The words that the parser has marked as variable assignments (those
preceding the command name) and redirections are saved for later
processing.
-
The words that are not variable assignments or redirections are
expanded (see section 3.5 Shell Expansions).
If any words remain after expansion, the first word
is taken to be the name of the command and the remaining words are
the arguments.
-
Redirections are performed as described above (see section 3.6 Redirections).
-
The text after the `=' in each variable assignment undergoes tilde
expansion, parameter expansion, command substitution, arithmetic expansion,
and quote removal before being assigned to the variable.
If no command name results, the variable assignments affect the current
shell environment. Otherwise, the variables are added to the environment
of the executed command and do not affect the current shell environment.
If any of the assignments attempts to assign a value to a readonly variable,
an error occurs, and the command exits with a non-zero status.
If no command name results, redirections are performed, but do not
affect the current shell environment. A redirection error causes the
command to exit with a non-zero status.
If there is a command name left after expansion, execution proceeds as
described below. Otherwise, the command exits. If one of the expansions
contained a command substitution, the exit status of the command is
the exit status of the last command substitution performed. If there
were no command substitutions, the command exits with a status of zero.
3.7.2 Command Search and Execution
After a command has been split into words, if it results in a
simple command and an optional list of arguments, the following
actions are taken.
-
If the command name contains no slashes, the shell attempts to
locate it. If there exists a shell function by that name, that
function is invoked as described in 3.3 Shell Functions.
-
If the name does not match a function, the shell searches for
it in the list of shell builtins. If a match is found, that
builtin is invoked.
-
If the name is neither a shell function nor a builtin,
and contains no slashes, Bash searches each element of
$PATH
for a directory containing an executable file
by that name. Bash uses a hash table to remember the full
pathnames of executable files to avoid multiple PATH
searches
(see the description of hash
in 4.1 Bourne Shell Builtins).
A full search of the directories in $PATH
is performed only if the command is not found in the hash table.
If the search is unsuccessful, the shell searches for a defined shell
function named command_not_found_handle
.
If that function exists, it is invoked with the original command and
the original command's arguments as its arguments, and the function's
exit status becomes the exit status of the shell.
If that function is not defined, the shell prints an error
message and returns an exit status of 127.
-
If the search is successful, or if the command name contains
one or more slashes, the shell executes the named program in
a separate execution environment.
Argument 0 is set to the name given, and the remaining arguments
to the command are set to the arguments supplied, if any.
-
If this execution fails because the file is not in executable
format, and the file is not a directory, it is assumed to be a
shell script and the shell executes it as described in
3.8 Shell Scripts.
-
If the command was not begun asynchronously, the shell waits for
the command to complete and collects its exit status.
3.7.3 Command Execution Environment
The shell has an execution environment, which consists of the
following:
-
open files inherited by the shell at invocation, as modified by
redirections supplied to the
exec
builtin
-
the current working directory as set by
cd
, pushd
, or
popd
, or inherited by the shell at invocation
-
the file creation mode mask as set by
umask
or inherited from
the shell's parent
-
current traps set by
trap
-
shell parameters that are set by variable assignment or with
set
or inherited from the shell's parent in the environment
-
shell functions defined during execution or inherited from the shell's
parent in the environment
-
options enabled at invocation (either by default or with command-line
arguments) or by
set
-
options enabled by
shopt
(see section 4.3.2 The Shopt Builtin)
-
shell aliases defined with
alias
(see section 6.6 Aliases)
-
various process IDs, including those of background jobs
(see section 3.2.3 Lists of Commands), the value of
$$
, and the value of
$PPID
When a simple command other than a builtin or shell function
is to be executed, it
is invoked in a separate execution environment that consists of
the following. Unless otherwise noted, the values are inherited
from the shell.
-
the shell's open files, plus any modifications and additions specified
by redirections to the command
-
the current working directory
-
the file creation mode mask
-
shell variables and functions marked for export, along with variables
exported for the command, passed in the environment (see section 3.7.4 Environment)
-
traps caught by the shell are reset to the values inherited from the
shell's parent, and traps ignored by the shell are ignored
A command invoked in this separate environment cannot affect the
shell's execution environment.
Command substitution, commands grouped with parentheses,
and asynchronous commands are invoked in a
subshell environment that is a duplicate of the shell environment,
except that traps caught by the shell are reset to the values
that the shell inherited from its parent at invocation. Builtin
commands that are invoked as part of a pipeline are also executed
in a subshell environment. Changes made to the subshell environment
cannot affect the shell's execution environment.
Subshells spawned to execute command substitutions inherit the value of
the `-e' option from the parent shell. When not in POSIX mode,
Bash clears the `-e' option in such subshells.
If a command is followed by a `&' and job control is not active, the
default standard input for the command is the empty file `/dev/null'.
Otherwise, the invoked command inherits the file descriptors of the calling
shell as modified by redirections.
3.7.4 Environment
When a program is invoked it is given an array of strings
called the environment.
This is a list of name-value pairs, of the form name=value
.
Bash provides several ways to manipulate the environment.
On invocation, the shell scans its own environment and
creates a parameter for each name found, automatically marking
it for export
to child processes. Executed commands inherit the environment.
The export
and `declare -x'
commands allow parameters and functions to be added to and
deleted from the environment. If the value of a parameter
in the environment is modified, the new value becomes part
of the environment, replacing the old. The environment
inherited by any executed command consists of the shell's
initial environment, whose values may be modified in the shell,
less any pairs removed by the unset
and `export -n'
commands, plus any additions via the export
and
`declare -x' commands.
The environment for any simple command
or function may be augmented temporarily by prefixing it with
parameter assignments, as described in 3.4 Shell Parameters.
These assignment statements affect only the environment seen
by that command.
If the `-k' option is set (see section 4.3.1 The Set Builtin), then all
parameter assignments are placed in the environment for a command,
not just those that precede the command name.
When Bash invokes an external command, the variable `$_'
is set to the full pathname of the command and passed to that
command in its environment.
3.7.5 Exit Status
The exit status of an executed command is the value returned by the
waitpid system call or equivalent function. Exit statuses
fall between 0 and 255, though, as explained below, the shell may
use values above 125 specially. Exit statuses from shell builtins and
compound commands are also limited to this range. Under certain
circumstances, the shell will use special values to indicate specific
failure modes.
For the shell's purposes, a command which exits with a
zero exit status has succeeded.
A non-zero exit status indicates failure.
This seemingly counter-intuitive scheme is used so there
is one well-defined way to indicate success and a variety of
ways to indicate various failure modes.
When a command terminates on a fatal signal whose number is N,
Bash uses the value 128+N as the exit status.
If a command is not found, the child process created to
execute it returns a status of 127. If a command is found
but is not executable, the return status is 126.
If a command fails because of an error during expansion or redirection,
the exit status is greater than zero.
The exit status is used by the Bash conditional commands
(see section 3.2.4.2 Conditional Constructs) and some of the list
constructs (see section 3.2.3 Lists of Commands).
All of the Bash builtins return an exit status of zero if they succeed
and a non-zero status on failure, so they may be used by the
conditional and list constructs.
All builtins return an exit status of 2 to indicate incorrect usage.
3.7.6 Signals
When Bash is interactive, in the absence of any traps, it ignores
SIGTERM
(so that `kill 0' does not kill an interactive shell),
and SIGINT
is caught and handled (so that the wait
builtin is interruptible).
When Bash receives a SIGINT
, it breaks out of any executing loops.
In all cases, Bash ignores SIGQUIT
.
If job control is in effect (see section 7. Job Control), Bash
ignores SIGTTIN
, SIGTTOU
, and SIGTSTP
.
Non-builtin commands started by Bash have signal handlers set to the
values inherited by the shell from its parent.
When job control is not in effect, asynchronous commands
ignore SIGINT
and SIGQUIT
in addition to these inherited
handlers.
Commands run as a result of
command substitution ignore the keyboard-generated job control signals
SIGTTIN
, SIGTTOU
, and SIGTSTP
.
The shell exits by default upon receipt of a SIGHUP
.
Before exiting, an interactive shell resends the SIGHUP
to
all jobs, running or stopped.
Stopped jobs are sent SIGCONT
to ensure that they receive
the SIGHUP
.
To prevent the shell from sending the SIGHUP
signal to a
particular job, it should be removed
from the jobs table with the disown
builtin (see section 7.2 Job Control Builtins) or marked
to not receive SIGHUP
using disown -h
.
If the huponexit
shell option has been set with shopt
(see section 4.3.2 The Shopt Builtin), Bash sends a SIGHUP
to all jobs when
an interactive login shell exits.
If Bash is waiting for a command to complete and receives a signal
for which a trap has been set, the trap will not be executed until
the command completes.
When Bash is waiting for an asynchronous
command via the wait
builtin, the reception of a signal for
which a trap has been set will cause the wait
builtin to return
immediately with an exit status greater than 128, immediately after
which the trap is executed.
3.8 Shell Scripts
A shell script is a text file containing shell commands. When such
a file is used as the first non-option argument when invoking Bash,
and neither the `-c' nor `-s' option is supplied
(see section 6.1 Invoking Bash),
Bash reads and executes commands from the file, then exits. This
mode of operation creates a non-interactive shell. The shell first
searches for the file in the current directory, and looks in the
directories in $PATH
if not found there.
When Bash runs
a shell script, it sets the special parameter 0
to the name
of the file, rather than the name of the shell, and the positional
parameters are set to the remaining arguments, if any are given.
If no additional arguments are supplied, the positional parameters
are unset.
A shell script may be made executable by using the chmod
command
to turn on the execute bit. When Bash finds such a file while
searching the $PATH
for a command, it spawns a subshell to
execute it. In other words, executing
is equivalent to executing
if filename
is an executable shell script.
This subshell reinitializes itself, so that the effect is as if a
new shell had been invoked to interpret the script, with the
exception that the locations of commands remembered by the parent
(see the description of hash
in 4.1 Bourne Shell Builtins)
are retained by the child.
Most versions of Unix make this a part of the operating system's command
execution mechanism. If the first line of a script begins with
the two characters `#!', the remainder of the line specifies
an interpreter for the program.
Thus, you can specify Bash, awk
, Perl, or some other
interpreter and write the rest of the script file in that language.
The arguments to the interpreter
consist of a single optional argument following the interpreter
name on the first line of the script file, followed by the name of
the script file, followed by the rest of the arguments. Bash
will perform this action on operating systems that do not handle it
themselves. Note that some older versions of Unix limit the interpreter
name and argument to a maximum of 32 characters.
Bash scripts often begin with #! /bin/bash
(assuming that
Bash has been installed in `/bin'), since this ensures that
Bash will be used to interpret the script, even if it is executed
under another shell.
4. Shell Builtin Commands
Builtin commands are contained within the shell itself.
When the name of a builtin command is used as the first word of
a simple command (see section 3.2.1 Simple Commands), the shell executes
the command directly, without invoking another program.
Builtin commands are necessary to implement functionality impossible
or inconvenient to obtain with separate utilities.
This section briefly describes the builtins which Bash inherits from
the Bourne Shell, as well as the builtin commands which are unique
to or have been extended in Bash.
Several builtin commands are described in other chapters: builtin
commands which provide the Bash interface to the job control
facilities (see section 7.2 Job Control Builtins), the directory stack
(see section 6.8.1 Directory Stack Builtins), the command history
(see section 9.2 Bash History Builtins), and the programmable completion
facilities (see section 8.7 Programmable Completion Builtins).
Many of the builtins have been extended by POSIX or Bash.
Unless otherwise noted, each builtin command documented as accepting
options preceded by `-' accepts `--'
to signify the end of the options.
The :
, true
, false
, and test
builtins do not accept options and do not treat `--' specially.
The exit
, logout
, break
, continue
, let
,
and shift
builtins accept and process arguments beginning
with `-' without requiring `--'.
Other builtins that accept arguments but are not specified as accepting
options interpret arguments beginning with `-' as invalid options and
require `--' to prevent this interpretation.
4.1 Bourne Shell Builtins
The following shell builtin commands are inherited from the Bourne Shell.
These commands are implemented as specified by the POSIX standard.
: (a colon)
-
Do nothing beyond expanding arguments and performing redirections.
The return status is zero.
. (a period)
-
Read and execute commands from the filename argument in the
current shell context. If filename does not contain a slash,
the PATH
variable is used to find filename.
When Bash is not in POSIX mode, the current directory is searched
if filename is not found in $PATH
.
If any arguments are supplied, they become the positional
parameters when filename is executed. Otherwise the positional
parameters are unchanged.
The return status is the exit status of the last command executed, or
zero if no commands are executed. If filename is not found, or
cannot be read, the return status is non-zero.
This builtin is equivalent to source
.
break
-
Exit from a for
, while
, until
, or select
loop.
If n is supplied, the nth enclosing loop is exited.
n must be greater than or equal to 1.
The return status is zero unless n is not greater than or equal to 1.
cd
-
| cd [-L|[-P [-e]] [-@] [directory]
|
Change the current working directory to directory.
If directory is not supplied, the value of the HOME
shell variable is used.
Any additional arguments following directory are ignored.
If the shell variable
CDPATH
exists, it is used as a search path:
each directory name in CDPATH
is searched for
directory, with alternative directory names in CDPATH
separated by a colon (`:').
If directory begins with a slash, CDPATH
is not used.
The `-P' option means to not follow symbolic links: symbolic links
are resolved while cd
is traversing directory and before
processing an instance of `..' in directory.
By default, or when the `-L' option is supplied, symbolic links
in directory are resolved after cd
processes an instance
of `..' in directory.
If `..' appears in directory, it is processed by removing the
immediately preceding pathname component, back to a slash or the beginning
of directory.
If the `-e' option is supplied with `-P'
and the current working directory cannot be successfully determined
after a successful directory change, cd
will return an unsuccessful
status.
On systems that support it, the `-@' option presents the extended
attributes associated with a file as a directory.
If directory is `-', it is converted to $OLDPWD
before the directory change is attempted.
If a non-empty directory name from CDPATH
is used, or if
`-' is the first argument, and the directory change is
successful, the absolute pathname of the new working directory is
written to the standard output.
The return status is zero if the directory is successfully changed,
non-zero otherwise.
continue
-
Resume the next iteration of an enclosing for
, while
,
until
, or select
loop.
If n is supplied, the execution of the nth enclosing loop
is resumed.
n must be greater than or equal to 1.
The return status is zero unless n is not greater than or equal to 1.
eval
-
The arguments are concatenated together into a single command, which is
then read and executed, and its exit status returned as the exit status
of eval
.
If there are no arguments or only empty arguments, the return status is
zero.
exec
-
| exec [-cl] [-a name] [command [arguments]]
|
If command
is supplied, it replaces the shell without creating a new process.
If the `-l' option is supplied, the shell places a dash at the
beginning of the zeroth argument passed to command.
This is what the login
program does.
The `-c' option causes command to be executed with an empty
environment.
If `-a' is supplied, the shell passes name as the zeroth
argument to command.
If command
cannot be executed for some reason, a non-interactive shell exits,
unless the execfail
shell option
is enabled. In that case, it returns failure.
An interactive shell returns failure if the file cannot be executed.
If no command is specified, redirections may be used to affect
the current shell environment. If there are no redirection errors, the
return status is zero; otherwise the return status is non-zero.
exit
-
Exit the shell, returning a status of n to the shell's parent.
If n is omitted, the exit status is that of the last command executed.
Any trap on EXIT
is executed before the shell terminates.
export
-
| export [-fn] [-p] [name[=value]]
|
Mark each name to be passed to child processes
in the environment. If the `-f' option is supplied, the names
refer to shell functions; otherwise the names refer to shell variables.
The `-n' option means to no longer mark each name for export.
If no names are supplied, or if the `-p' option is given, a
list of names of all exported variables is displayed.
The `-p' option displays output in a form that may be reused as input.
If a variable name is followed by =value, the value of
the variable is set to value.
The return status is zero unless an invalid option is supplied, one of
the names is not a valid shell variable name, or `-f' is supplied
with a name that is not a shell function.
getopts
-
| getopts optstring name [args]
|
getopts
is used by shell scripts to parse positional parameters.
optstring contains the option characters to be recognized; if a
character is followed by a colon, the option is expected to have an
argument, which should be separated from it by whitespace.
The colon (`:') and question mark (`?') may not be
used as option characters.
Each time it is invoked, getopts
places the next option in the shell variable name, initializing
name if it does not exist,
and the index of the next argument to be processed into the
variable OPTIND
.
OPTIND
is initialized to 1 each time the shell or a shell script
is invoked.
When an option requires an argument,
getopts
places that argument into the variable OPTARG
.
The shell does not reset OPTIND
automatically; it must be manually
reset between multiple calls to getopts
within the same shell
invocation if a new set of parameters is to be used.
When the end of options is encountered, getopts
exits with a
return value greater than zero.
OPTIND
is set to the index of the first non-option argument,
and name is set to `?'.
getopts
normally parses the positional parameters, but if more arguments are
given in args, getopts
parses those instead.
getopts
can report errors in two ways. If the first character of
optstring is a colon, silent
error reporting is used. In normal operation, diagnostic messages
are printed when invalid options or missing option arguments are
encountered.
If the variable OPTERR
is set to 0, no error messages will be displayed, even if the first
character of optstring
is not a colon.
If an invalid option is seen,
getopts
places `?' into name and, if not silent,
prints an error message and unsets OPTARG
.
If getopts
is silent, the option character found is placed in
OPTARG
and no diagnostic message is printed.
If a required argument is not found, and getopts
is not silent, a question mark (`?') is placed in name,
OPTARG
is unset, and a diagnostic message is printed.
If getopts
is silent, then a colon (`:') is placed in
name and OPTARG
is set to the option character found.
hash
-
| hash [-r] [-p filename] [-dt] [name]
|
Each time hash
is invoked, it remembers the full pathnames of the
commands specified as name arguments,
so they need not be searched for on subsequent invocations.
The commands are found by searching through the directories listed in
$PATH
.
Any previously-remembered pathname is discarded.
The `-p' option inhibits the path search, and filename is
used as the location of name.
The `-r' option causes the shell to forget all remembered locations.
The `-d' option causes the shell to forget the remembered location
of each name.
If the `-t' option is supplied, the full pathname to which each
name corresponds is printed. If multiple name arguments are
supplied with `-t' the name is printed before the hashed
full pathname.
The `-l' option causes output to be displayed in a format
that may be reused as input.
If no arguments are given, or if only `-l' is supplied,
information about remembered commands is printed.
The return status is zero unless a name is not found or an invalid
option is supplied.
pwd
-
Print the absolute pathname of the current working directory.
If the `-P' option is supplied, the pathname printed will not
contain symbolic links.
If the `-L' option is supplied, the pathname printed may contain
symbolic links.
The return status is zero unless an error is encountered while
determining the name of the current directory or an invalid option
is supplied.
readonly
-
| readonly [-aAf] [-p] [name[=value]] ...
|
Mark each name as readonly.
The values of these names may not be changed by subsequent assignment.
If the `-f' option is supplied, each name refers to a shell
function.
The `-a' option means each name refers to an indexed
array variable; the `-A' option means each name refers
to an associative array variable.
If both options are supplied, `-A' takes precedence.
If no name arguments are given, or if the `-p'
option is supplied, a list of all readonly names is printed.
The other options may be used to restrict the output to a subset of
the set of readonly names.
The `-p' option causes output to be displayed in a format that
may be reused as input.
If a variable name is followed by =value, the value of
the variable is set to value.
The return status is zero unless an invalid option is supplied, one of
the name arguments is not a valid shell variable or function name,
or the `-f' option is supplied with a name that is not a shell function.
return
-
Cause a shell function to stop executing and return the value n
to its caller.
If n is not supplied, the return value is the exit status of the
last command executed in the function.
return
may also be used to terminate execution of a script
being executed with the .
(source
) builtin,
returning either n or
the exit status of the last command executed within the script as the exit
status of the script.
If n is supplied, the return value is its least significant
8 bits.
Any command associated with the RETURN
trap is executed
before execution resumes after the function or script.
The return status is non-zero if return
is supplied a non-numeric
argument or is used outside a function
and not during the execution of a script by .
or source
.
shift
-
Shift the positional parameters to the left by n.
The positional parameters from n+1 ... $#
are
renamed to $1
... $#
-n.
Parameters represented by the numbers $#
to $#
-n+1
are unset.
n must be a non-negative number less than or equal to $#
.
If n is zero or greater than $#
, the positional parameters
are not changed.
If n is not supplied, it is assumed to be 1.
The return status is zero unless n is greater than $#
or
less than zero, non-zero otherwise.
test
[
-
Evaluate a conditional express
ion expr and return a status of 0
(true) or 1 (false).
Each operator and operand must be a separate argument.
Expressions are composed of the primaries described below in
6.4 Bash Conditional Expressions.
test
does not accept any options, nor does it accept and ignore
an argument of `--' as signifying the end of options.
When the [
form is used, the last argument to the command must
be a ]
.
Expressions may be combined using the following operators, listed in
decreasing order of precedence.
The evaluation depends on the number of arguments; see below.
Operator precedence is used when there are five or more arguments.
! expr
- True if expr is false.
( expr )
- Returns the value of expr.
This may be used to override the normal precedence of operators.
expr1 -a expr2
- True if both expr1 and expr2 are true.
expr1 -o expr2
- True if either expr1 or expr2 is true.
The test
and [
builtins evaluate conditional
expressions using a set of rules based on the number of arguments.
- 0 arguments
- The expression is false.
- 1 argument
- The expression is true if and only if the argument is not null.
- 2 arguments
- If the first argument is `!', the expression is true if and
only if the second argument is null.
If the first argument is one of the unary conditional operators
(see section 6.4 Bash Conditional Expressions), the expression
is true if the unary test is true.
If the first argument is not a valid unary operator, the expression is
false.
- 3 arguments
- The following conditions are applied in the order listed.
If the second argument is one of the binary conditional
operators (see section 6.4 Bash Conditional Expressions), the
result of the expression is the result of the binary test using the
first and third arguments as operands.
The `-a' and `-o' operators are considered binary operators
when there are three arguments.
If the first argument is `!', the value is the negation of
the two-argument test using the second and third arguments.
If the first argument is exactly `(' and the third argument is
exactly `)', the result is the one-argument test of the second
argument.
Otherwise, the expression is false.
- 4 arguments
- If the first argument is `!', the result is the negation of
the three-argument expression composed of the remaining arguments.
Otherwise, the expression is parsed and evaluated according to
precedence using the rules listed above.
- 5 or more arguments
- The expression is parsed and evaluated according to precedence
using the rules listed above.
When used with test
or `[', the `<' and `>'
operators sort lexicographically using ASCII ordering.
times
-
Print out the user and system times used by the shell and its children.
The return status is zero.
trap
-
| trap [-lp] [arg] [sigspec ...]
|
The commands in arg are to be read and executed when the
shell receives signal sigspec. If arg is absent (and
there is a single sigspec) or
equal to `-', each specified signal's disposition is reset
to the value it had when the shell was started.
If arg is the null string, then the signal specified by
each sigspec is ignored by the shell and commands it invokes.
If arg is not present and `-p' has been supplied,
the shell displays the trap commands associated with each sigspec.
If no arguments are supplied, or
only `-p' is given, trap
prints the list of commands
associated with each signal number in a form that may be reused as
shell input.
The `-l' option causes the shell to print a list of signal names
and their corresponding numbers.
Each sigspec is either a signal name or a signal number.
Signal names are case insensitive and the SIG
prefix is optional.
If a sigspec
is 0
or EXIT
, arg is executed when the shell exits.
If a sigspec is DEBUG
, the command arg is executed
before every simple command, for
command, case
command,
select
command, every arithmetic for
command, and before
the first command executes in a shell function.
Refer to the description of the extdebug
option to the
shopt
builtin (see section 4.3.2 The Shopt Builtin) for details of its
effect on the DEBUG
trap.
If a sigspec is RETURN
, the command arg is executed
each time a shell function or a script executed with the .
or
source
builtins finishes executing.
If a sigspec is ERR
, the command arg
is executed whenever
a pipeline (which may consist of a single simple
command), a list, or a compound command returns a
non-zero exit status,
subject to the following conditions.
The ERR
trap is not executed if the failed command is part of the
command list immediately following an until
or while
keyword,
part of the test following the if
or elif
reserved words,
part of a command executed in a &&
or ||
list
except the command following the final &&
or ||
,
any command in a pipeline but the last,
or if the command's return
status is being inverted using !
.
These are the same conditions obeyed by the errexit
(`-e')
option.
Signals ignored upon entry to the shell cannot be trapped or reset.
Trapped signals that are not being ignored are reset to their original
values in a subshell or subshell environment when one is created.
The return status is zero unless a sigspec does not specify a
valid signal.
umask
-
Set the shell process's file creation mask to mode. If
mode begins with a digit, it is interpreted as an octal number;
if not, it is interpreted as a symbolic mode mask similar
to that accepted by the chmod
command. If mode is
omitted, the current value of the mask is printed. If the `-S'
option is supplied without a mode argument, the mask is printed
in a symbolic format.
If the `-p' option is supplied, and mode
is omitted, the output is in a form that may be reused as input.
The return status is zero if the mode is successfully changed or if
no mode argument is supplied, and non-zero otherwise.
Note that when the mode is interpreted as an octal number, each number
of the umask is subtracted from 7
. Thus, a umask of 022
results in permissions of 755
.
unset
-
Remove each variable or function name.
If the `-v' option is given, each
name refers to a shell variable and that variable is remvoved.
If the `-f' option is given, the names refer to shell
functions, and the function definition is removed.
If the `-n' option is supplied, and name is a variable with
the nameref attribute, name will be unset rather than the
variable it references.
`-n' has no effect if the `-f' option is supplied.
If no options are supplied, each name refers to a variable; if
there is no variable by that name, any function with that name is
unset.
Readonly variables and functions may not be unset.
The return status is zero unless a name is readonly.
4.2 Bash Builtin Commands
This section describes builtin commands which are unique to
or have been extended in Bash.
Some of these commands are specified in the POSIX standard.
alias
-
| alias [-p] [name[=value] ...]
|
Without arguments or with the `-p' option, alias
prints
the list of aliases on the standard output in a form that allows
them to be reused as input.
If arguments are supplied, an alias is defined for each name
whose value is given. If no value is given, the name
and value of the alias is printed.
Aliases are described in 6.6 Aliases.
bind
-
| bind [-m keymap] [-lpsvPSVX]
bind [-m keymap] [-q function] [-u function] [-r keyseq]
bind [-m keymap] -f filename
bind [-m keymap] -x keyseq:shell-command
bind [-m keymap] keyseq:function-name
bind readline-command
|
Display current Readline (see section 8. Command Line Editing)
key and function bindings,
bind a key sequence to a Readline function or macro,
or set a Readline variable.
Each non-option argument is a command as it would appear in a
Readline initialization file (see section 8.3 Readline Init File),
but each binding or command must be passed as a separate argument; e.g.,
`"\C-x\C-r":re-read-init-file'.
Options, if supplied, have the following meanings:
-m keymap
- Use keymap as the keymap to be affected by
the subsequent bindings. Acceptable keymap
names are
emacs
,
emacs-standard
,
emacs-meta
,
emacs-ctlx
,
vi
,
vi-move
,
vi-command
, and
vi-insert
.
vi
is equivalent to vi-command
;
emacs
is equivalent to emacs-standard
.
-l
- List the names of all Readline functions.
-p
- Display Readline function names and bindings in such a way that they
can be used as input or in a Readline initialization file.
-P
- List current Readline function names and bindings.
-v
- Display Readline variable names and values in such a way that they
can be used as input or in a Readline initialization file.
-V
- List current Readline variable names and values.
-s
- Display Readline key sequences bound to macros and the strings they output
in such a way that they can be used as input or in a Readline
initialization file.
-S
- Display Readline key sequences bound to macros and the strings they output.
-f filename
- Read key bindings from filename.
-q function
- Query about which keys invoke the named function.
-u function
- Unbind all keys bound to the named function.
-r keyseq
- Remove any current binding for keyseq.
-x keyseq:shell-command
- Cause shell-command to be executed whenever keyseq is
entered.
When shell-command is executed, the shell sets the
READLINE_LINE
variable to the contents of the Readline line
buffer and the READLINE_POINT
variable to the current location
of the insertion point.
If the executed command changes the value of READLINE_LINE
or
READLINE_POINT
, those new values will be reflected in the
editing state.
-X
- List all key sequences bound to shell commands and the associated commands
in a format that can be reused as input.
The return status is zero unless an invalid option is supplied or an
error occurs.
builtin
-
| builtin [shell-builtin [args]]
|
Run a shell builtin, passing it args, and return its exit status.
This is useful when defining a shell function with the same
name as a shell builtin, retaining the functionality of the builtin within
the function.
The return status is non-zero if shell-builtin is not a shell
builtin command.
caller
-
Returns the context of any active subroutine call (a shell function or
a script executed with the .
or source
builtins).
Without expr, caller
displays the line number and source
filename of the current subroutine call.
If a non-negative integer is supplied as expr, caller
displays the line number, subroutine name, and source file corresponding
to that position in the current execution call stack. This extra
information may be used, for example, to print a stack trace. The
current frame is frame 0.
The return value is 0 unless the shell is not executing a subroutine
call or expr does not correspond to a valid position in the
call stack.
command
-
| command [-pVv] command [arguments ...]
|
Runs command with arguments ignoring any shell function
named command.
Only shell builtin commands or commands found by searching the
PATH
are executed.
If there is a shell function named ls
, running `command ls'
within the function will execute the external command ls
instead of calling the function recursively.
The `-p' option means to use a default value for PATH
that is guaranteed to find all of the standard utilities.
The return status in this case is 127 if command cannot be
found or an error occurred, and the exit status of command
otherwise.
If either the `-V' or `-v' option is supplied, a
description of command is printed. The `-v' option
causes a single word indicating the command or file name used to
invoke command to be displayed; the `-V' option produces
a more verbose description. In this case, the return status is
zero if command is found, and non-zero if not.
declare
-
| declare [-aAfFgilnrtux] [-p] [name[=value] ...]
|
Declare variables and give them attributes. If no names
are given, then display the values of variables instead.
The `-p' option will display the attributes and values of each
name.
When `-p' is used with name arguments, additional options,
other than `-f' and `-F', are ignored.
When `-p' is supplied without name arguments, declare
will display the attributes and values of all variables having the
attributes specified by the additional options.
If no other options are supplied with `-p', declare
will
display the attributes and values of all shell variables. The `-f'
option will restrict the display to shell functions.
The `-F' option inhibits the display of function definitions;
only the function name and attributes are printed.
If the extdebug
shell option is enabled using shopt
(see section 4.3.2 The Shopt Builtin), the source file name and line number where
the function is defined are displayed as well.
`-F' implies `-f'.
The `-g' option forces variables to be created or modified at
the global scope, even when declare
is executed in a shell function.
It is ignored in all other cases.
The following options can be used to restrict output to variables with
the specified attributes or to give variables attributes:
-a
- Each name is an indexed array variable (see section 6.7 Arrays).
-A
- Each name is an associative array variable (see section 6.7 Arrays).
-f
- Use function names only.
-i
- The variable is to be treated as
an integer; arithmetic evaluation (see section 6.5 Shell Arithmetic) is
performed when the variable is assigned a value.
-l
- When the variable is assigned a value, all upper-case characters are
converted to lower-case.
The upper-case attribute is disabled.
-n
- Give each name the nameref attribute, making
it a name reference to another variable.
That other variable is defined by the value of name.
All references and assignments to name, except for changing the
`-n' attribute itself, are performed on the variable referenced by
name's value.
The `-n' attribute cannot be applied to array variables.
-r
- Make names readonly. These names cannot then be assigned values
by subsequent assignment statements or unset.
-t
- Give each name the
trace
attribute.
Traced functions inherit the DEBUG
and RETURN
traps from
the calling shell.
The trace attribute has no special meaning for variables.
-u
- When the variable is assigned a value, all lower-case characters are
converted to upper-case.
The lower-case attribute is disabled.
-x
- Mark each name for export to subsequent commands via
the environment.
Using `+' instead of `-' turns off the attribute instead,
with the exceptions that `+a'
may not be used to destroy an array variable and `+r' will not
remove the readonly attribute.
When used in a function, declare
makes each name local,
as with the local
command, unless the `-g' option is used.
If a variable name is followed by =value, the value of the variable
is set to value.
When using `-a' or `-A' and the compound assignment syntax to
create array variables, additional attributes do not take effect until
subsequent assignments.
The return status is zero unless an invalid option is encountered,
an attempt is made to define a function using `-f foo=bar',
an attempt is made to assign a value to a readonly variable,
an attempt is made to assign a value to an array variable without
using the compound assignment syntax (see section 6.7 Arrays),
one of the names is not a valid shell variable name,
an attempt is made to turn off readonly status for a readonly variable,
an attempt is made to turn off array status for an array variable,
or an attempt is made to display a non-existent function with `-f'.
echo
-
Output the args, separated by spaces, terminated with a
newline.
The return status is 0 unless a write error occurs.
If `-n' is specified, the trailing newline is suppressed.
If the `-e' option is given, interpretation of the following
backslash-escaped characters is enabled.
The `-E' option disables the interpretation of these escape characters,
even on systems where they are interpreted by default.
The xpg_echo
shell option may be used to
dynamically determine whether or not echo
expands these
escape characters by default.
echo
does not interpret `--' to mean the end of options.
echo
interprets the following escape sequences:
\a
- alert (bell)
\b
- backspace
\c
- suppress further output
\e
\E
- escape
\f
- form feed
\n
- new line
\r
- carriage return
\t
- horizontal tab
\v
- vertical tab
\\
- backslash
\0nnn
- the eight-bit character whose value is the octal value nnn
(zero to three octal digits)
\xHH
- the eight-bit character whose value is the hexadecimal value HH
(one or two hex digits)
\uHHHH
- the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
HHHH (one to four hex digits)
\UHHHHHHHH
- the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
HHHHHHHH (one to eight hex digits)
enable
-
| enable [-a] [-dnps] [-f filename] [name ...]
|
Enable and disable builtin shell commands.
Disabling a builtin allows a disk command which has the same name
as a shell builtin to be executed without specifying a full pathname,
even though the shell normally searches for builtins before disk commands.
If `-n' is used, the names become disabled. Otherwise
names are enabled. For example, to use the test
binary
found via $PATH
instead of the shell builtin version, type
`enable -n test'.
If the `-p' option is supplied, or no name arguments appear,
a list of shell builtins is printed. With no other arguments, the list
consists of all enabled shell builtins.
The `-a' option means to list
each builtin with an indication of whether or not it is enabled.
The `-f' option means to load the new builtin command name
from shared object filename, on systems that support dynamic loading.
The `-d' option will delete a builtin loaded with `-f'.
If there are no options, a list of the shell builtins is displayed.
The `-s' option restricts enable
to the POSIX special
builtins. If `-s' is used with `-f', the new builtin becomes
a special builtin (see section 4.4 Special Builtins).
The return status is zero unless a name is not a shell builtin
or there is an error loading a new builtin from a shared object.
help
-
Display helpful information about builtin commands.
If pattern is specified, help
gives detailed help
on all commands matching pattern, otherwise a list of
the builtins is printed.
Options, if supplied, have the following meanings:
-d
- Display a short description of each pattern
-m
- Display the description of each pattern in a manpage-like format
-s
- Display only a short usage synopsis for each pattern
The return status is zero unless no command matches pattern.
let
-
| let expression [expression ...]
|
The let
builtin allows arithmetic to be performed on shell
variables. Each expression is evaluated according to the
rules given below in 6.5 Shell Arithmetic. If the
last expression evaluates to 0, let
returns 1;
otherwise 0 is returned.
local
-
| local [option] name[=value] ...
|
For each argument, a local variable named name is created,
and assigned value.
The option can be any of the options accepted by declare
.
local
can only be used within a function; it makes the variable
name have a visible scope restricted to that function and its
children. The return status is zero unless local
is used outside
a function, an invalid name is supplied, or name is a
readonly variable.
logout
-
Exit a login shell, returning a status of n to the shell's
parent.
mapfile
-
| mapfile [-n count] [-O origin] [-s count] [-t] [-u fd]
[-C callback] [-c quantum] [array]
|
Read lines from the standard input into the indexed array variable array,
or from file descriptor fd
if the `-u' option is supplied.
The variable MAPFILE
is the default array.
Options, if supplied, have the following meanings:
-n
- Copy at most count lines. If count is 0, all lines are copied.
-O
- Begin assigning to array at index origin.
The default index is 0.
-s
- Discard the first count lines read.
-t
- Remove a trailing newline from each line read.
-u
- Read lines from file descriptor fd instead of the standard input.
-C
- Evaluate callback each time quantumP lines are read.
The `-c' option specifies quantum.
-c
- Specify the number of lines read between each call to callback.
If `-C' is specified without `-c',
the default quantum is 5000.
When callback is evaluated, it is supplied the index of the next
array element to be assigned and the line to be assigned to that element
as additional arguments.
callback is evaluated after the line is read but before the
array element is assigned.
If not supplied with an explicit origin, mapfile
will clear array
before assigning to it.
mapfile
returns successfully unless an invalid option or option
argument is supplied, array is invalid or unassignable, or array
is not an indexed array.
printf
-
| printf [-v var] format [arguments]
|
Write the formatted arguments to the standard output under the
control of the format.
The `-v' option causes the output to be assigned to the variable
var rather than being printed to the standard output.
The format is a character string which contains three types of objects:
plain characters, which are simply copied to standard output, character
escape sequences, which are converted and copied to the standard output, and
format specifications, each of which causes printing of the next successive
argument.
In addition to the standard printf(1)
formats, printf
interprets the following extensions:
%b
- Causes
printf
to expand backslash escape sequences in the
corresponding argument,
except that `\c' terminates output, backslashes in
`\'', `\"', and `\?' are not removed, and octal escapes
beginning with `\0' may contain up to four digits.
%q
- Causes
printf
to output the
corresponding argument in a format that can be reused as shell input.
%(datefmt)T
- Causes
printf
to output the date-time string resulting from using
datefmt as a format string for strftime
(3).
The corresponding argument is an integer representing the number of
seconds since the epoch.
Two special argument values may be used: -1 represents the current
time, and -2 represents the time the shell was invoked.
If no argument is specified, conversion behaves as if -1 had been given.
This is an exception to the usual printf
behavior.
Arguments to non-string format specifiers are treated as C language constants,
except that a leading plus or minus sign is allowed, and if the leading
character is a single or double quote, the value is the ASCII value of
the following character.
The format is reused as necessary to consume all of the arguments.
If the format requires more arguments than are supplied, the
extra format specifications behave as if a zero value or null string, as
appropriate, had been supplied. The return value is zero on success,
non-zero on failure.
read
-
| read [-ers] [-a aname] [-d delim] [-i text] [-n nchars]
[-N nchars] [-p prompt] [-t timeout] [-u fd] [name ...]
|
One line is read from the standard input, or from the file descriptor
fd supplied as an argument to the `-u' option, and the first word
is assigned to the first name, the second word to the second name,
and so on, with leftover words and their intervening separators assigned
to the last name.
If there are fewer words read from the input stream than names,
the remaining names are assigned empty values.
The characters in the value of the IFS
variable
are used to split the line into words using the same rules the shell
uses for expansion (described above in 3.5.7 Word Splitting).
The backslash character `\' may be used to remove any special
meaning for the next character read and for line continuation.
If no names are supplied, the line read is assigned to the
variable REPLY
.
The return code is zero, unless end-of-file is encountered, read
times out (in which case the return code is greater than 128),
a variable assignment error (such as assigning to a readonly variable) occurs,
or an invalid file descriptor is supplied as the argument to `-u'.
Options, if supplied, have the following meanings:
-a aname
- The words are assigned to sequential indices of the array variable
aname, starting at 0.
All elements are removed from aname before the assignment.
Other name arguments are ignored.
-d delim
- The first character of delim is used to terminate the input line,
rather than newline.
-e
- Readline (see section 8. Command Line Editing) is used to obtain the line.
Readline uses the current (or default, if line editing was not previously
active) editing settings.
-i text
- If Readline is being used to read the line, text is placed into
the editing buffer before editing begins.
-n nchars
read
returns after reading nchars characters rather than
waiting for a complete line of input, but honor a delimiter if fewer
than nchars characters are read before the delimiter.
-N nchars
read
returns after reading exactly nchars characters rather
than waiting for a complete line of input, unless EOF is encountered or
read
times out.
Delimiter characters encountered in the input are
not treated specially and do not cause read
to return until
nchars characters are read.
-p prompt
- Display prompt, without a trailing newline, before attempting
to read any input.
The prompt is displayed only if input is coming from a terminal.
-r
- If this option is given, backslash does not act as an escape character.
The backslash is considered to be part of the line.
In particular, a backslash-newline pair may not be used as a line
continuation.
-s
- Silent mode. If input is coming from a terminal, characters are
not echoed.
-t timeout
- Cause
read
to time out and return failure if a complete line of
input (or a specified number of characters)
is not read within timeout seconds.
timeout may be a decimal number with a fractional portion following
the decimal point.
This option is only effective if read
is reading input from a
terminal, pipe, or other special file; it has no effect when reading
from regular files.
If read
times out, read
saves any partial input read into
the specified variable name.
If timeout is 0, read
returns immediately, without trying to
read and data. The exit status is 0 if input is available on
the specified file descriptor, non-zero otherwise.
The exit status is greater than 128 if the timeout is exceeded.
-u fd
- Read input from file descriptor fd.
readarray
-
| readarray [-n count] [-O origin] [-s count] [-t] [-u fd]
[-C callback] [-c quantum] [array]
|
Read lines from the standard input into the indexed array variable array,
or from file descriptor fd
if the `-u' option is supplied.
A synonym for mapfile
.
source
-
A synonym for .
(see section 4.1 Bourne Shell Builtins).
type
-
For each name, indicate how it would be interpreted if used as a
command name.
If the `-t' option is used, type
prints a single word
which is one of `alias', `function', `builtin',
`file' or `keyword',
if name is an alias, shell function, shell builtin,
disk file, or shell reserved word, respectively.
If the name is not found, then nothing is printed, and
type
returns a failure status.
If the `-p' option is used, type
either returns the name
of the disk file that would be executed, or nothing if `-t'
would not return `file'.
The `-P' option forces a path search for each name, even if
`-t' would not return `file'.
If a command is hashed, `-p' and `-P' print the hashed value,
which is not necessarily the file that appears first in $PATH
.
If the `-a' option is used, type
returns all of the places
that contain an executable named file.
This includes aliases and functions, if and only if the `-p' option
is not also used.
If the `-f' option is used, type
does not attempt to find
shell functions, as with the command
builtin.
The return status is zero if all of the names are found, non-zero
if any are not found.
typeset
-
| typeset [-afFgrxilnrtux] [-p] [name[=value] ...]
|
The typeset
command is supplied for compatibility with the Korn
shell.
It is a synonym for the declare
builtin command.
ulimit
-
| ulimit [-abcdefilmnpqrstuvxHST] [limit]
|
ulimit
provides control over the resources available to processes
started by the shell, on systems that allow such control. If an
option is given, it is interpreted as follows:
-S
- Change and report the soft limit associated with a resource.
-H
- Change and report the hard limit associated with a resource.
-a
- All current limits are reported.
-b
- The maximum socket buffer size.
-c
- The maximum size of core files created.
-d
- The maximum size of a process's data segment.
-e
- The maximum scheduling priority ("nice").
-f
- The maximum size of files written by the shell and its children.
-i
- The maximum number of pending signals.
-l
- The maximum size that may be locked into memory.
-m
- The maximum resident set size (many systems do not honor this limit).
-n
- The maximum number of open file descriptors (most systems do not
allow this value to be set).
-p
- The pipe buffer size.
-q
- The maximum number of bytes in POSIX message queues.
-r
- The maximum real-time scheduling priority.
-s
- The maximum stack size.
-t
- The maximum amount of cpu time in seconds.
-u
- The maximum number of processes available to a single user.
-v
- The maximum amount of virtual memory available to the shell, and, on
some systems, to its children.
-x
- The maximum number of file locks.
-T
- The maximum number of threads.
If limit is given, and the `-a' option is not used,
limit is the new value of the specified resource.
The special limit values hard
, soft
, and
unlimited
stand for the current hard limit, the current soft limit,
and no limit, respectively.
A hard limit cannot be increased by a non-root user once it is set;
a soft limit may be increased up to the value of the hard limit.
Otherwise, the current value of the soft limit for the specified resource
is printed, unless the `-H' option is supplied.
When setting new limits, if neither `-H' nor `-S' is supplied,
both the hard and soft limits are set.
If no option is given, then `-f' is assumed. Values are in 1024-byte
increments, except for `-t', which is in seconds; `-p',
which is in units of 512-byte blocks; and `-T', `-b',
`-n' and `-u', which are unscaled values.
The return status is zero unless an invalid option or argument is supplied,
or an error occurs while setting a new limit.
unalias
-
Remove each name from the list of aliases. If `-a' is
supplied, all aliases are removed.
Aliases are described in 6.6 Aliases.
4.3 Modifying Shell Behavior
4.3.1 The Set Builtin
This builtin is so complicated that it deserves its own section. set
allows you to change the values of shell options and set the positional
parameters, or to display the names and values of shell variables.
set
-
| set [--abefhkmnptuvxBCEHPT] [-o option-name] [argument ...]
set [+abefhkmnptuvxBCEHPT] [+o option-name] [argument ...]
|
If no options or arguments are supplied, set
displays the names
and values of all shell variables and functions, sorted according to the
current locale, in a format that may be reused as input
for setting or resetting the currently-set variables.
Read-only variables cannot be reset.
In POSIX mode, only shell variables are listed.
When options are supplied, they set or unset shell attributes.
Options, if specified, have the following meanings:
-a
- Mark variables and function which are modified or created for export
to the environment of subsequent commands.
-b
- Cause the status of terminated background jobs to be reported
immediately, rather than before printing the next primary prompt.
-e
- Exit immediately if
a pipeline (see section 3.2.2 Pipelines), which may consist of a single simple command
(see section 3.2.1 Simple Commands),
a list (see section 3.2.3 Lists of Commands),
or a compound command (see section 3.2.4 Compound Commands)
returns a non-zero status.
The shell does not exit if the command that fails is part of the
command list immediately following a
while
or until
keyword,
part of the test in an if
statement,
part of any command executed in a &&
or ||
list except
the command following the final &&
or ||
,
any command in a pipeline but the last,
or if the command's return status is being inverted with !
.
If a compound command other than a subshell
returns a non-zero status because a command failed
while `-e' was being ignored, the shell does not exit.
A trap on ERR
, if set, is executed before the shell exits.
This option applies to the shell environment and each subshell environment
separately (see section 3.7.3 Command Execution Environment), and may cause
subshells to exit before executing all the commands in the subshell.
If a compound command or shell function executes in a context where
`-e' is being ignored,
none of the commands executed within the compound command or function body
will be affected by the `-e' setting, even if `-e' is set
and a command returns a failure status.
If a compound command or shell function sets `-e' while executing in
a context where `-e' is ignored, that setting will not have any
effect until the compound command or the command containing the function
call completes.
-f
- Disable filename expansion (globbing).
-h
- Locate and remember (hash) commands as they are looked up for execution.
This option is enabled by default.
-k
- All arguments in the form of assignment statements are placed
in the environment for a command, not just those that precede
the command name.
-m
- Job control is enabled (see section 7. Job Control).
All processes run in a separate process group.
When a background job completes, the shell prints a line
containing its exit status.
-n
- Read commands but do not execute them; this may be used to check a
script for syntax errors.
This option is ignored by interactive shells.
-o option-name
Set the option corresponding to option-name:
allexport
- Same as
-a
.
braceexpand
- Same as
-B
.
emacs
- Use an
emacs
-style line editing interface (see section 8. Command Line Editing).
This also affects the editing interface used for read -e
.
errexit
- Same as
-e
.
errtrace
- Same as
-E
.
functrace
- Same as
-T
.
hashall
- Same as
-h
.
histexpand
- Same as
-H
.
history
- Enable command history, as described in 9.1 Bash History Facilities.
This option is on by default in interactive shells.
ignoreeof
- An interactive shell will not exit upon reading EOF.
keyword
- Same as
-k
.
monitor
- Same as
-m
.
noclobber
- Same as
-C
.
noexec
- Same as
-n
.
noglob
- Same as
-f
.
nolog
- Currently ignored.
notify
- Same as
-b
.
nounset
- Same as
-u
.
onecmd
- Same as
-t
.
physical
- Same as
-P
.
pipefail
- If set, the return value of a pipeline is the value of the last
(rightmost) command to exit with a non-zero status, or zero if all
commands in the pipeline exit successfully.
This option is disabled by default.
posix
- Change the behavior of Bash where the default operation differs
from the POSIX standard to match the standard
(see section 6.11 Bash POSIX Mode).
This is intended to make Bash behave as a strict superset of that
standard.
privileged
- Same as
-p
.
verbose
- Same as
-v
.
vi
- Use a
vi
-style line editing interface.
This also affects the editing interface used for read -e
.
xtrace
- Same as
-x
.
-p
- Turn on privileged mode.
In this mode, the
$BASH_ENV
and $ENV
files are not
processed, shell functions are not inherited from the environment,
and the SHELLOPTS
, BASHOPTS
, CDPATH
and GLOBIGNORE
variables, if they appear in the environment, are ignored.
If the shell is started with the effective user (group) id not equal to the
real user (group) id, and the `-p' option is not supplied, these actions
are taken and the effective user id is set to the real user id.
If the `-p' option is supplied at startup, the effective user id is
not reset.
Turning this option off causes the effective user
and group ids to be set to the real user and group ids.
-t
- Exit after reading and executing one command.
-u
- Treat unset variables and parameters other than the special parameters
`@' or `*' as an error when performing parameter expansion.
An error message will be written to the standard error, and a non-interactive
shell will exit.
-v
- Print shell input lines as they are read.
-x
- Print a trace of simple commands,
for
commands, case
commands, select
commands, and arithmetic for
commands
and their arguments or associated word lists after they are
expanded and before they are executed. The value of the PS4
variable is expanded and the resultant value is printed before
the command and its expanded arguments.
-B
- The shell will perform brace expansion (see section 3.5.1 Brace Expansion).
This option is on by default.
-C
- Prevent output redirection using `>', `>&', and `<>'
from overwriting existing files.
-E
- If set, any trap on
ERR
is inherited by shell functions, command
substitutions, and commands executed in a subshell environment.
The ERR
trap is normally not inherited in such cases.
-H
- Enable `!' style history substitution (see section 9.3 History Expansion).
This option is on by default for interactive shells.
-P
- If set, do not resolve symbolic links when performing commands such as
cd
which change the current directory. The physical directory
is used instead. By default, Bash follows
the logical chain of directories when performing commands
which change the current directory.
For example, if `/usr/sys' is a symbolic link to `/usr/local/sys'
then:
| $ cd /usr/sys; echo $PWD
/usr/sys
$ cd ..; pwd
/usr
|
If set -P
is on, then:
| $ cd /usr/sys; echo $PWD
/usr/local/sys
$ cd ..; pwd
/usr/local
|
-T
- If set, any trap on
DEBUG
and RETURN
are inherited by
shell functions, command substitutions, and commands executed
in a subshell environment.
The DEBUG
and RETURN
traps are normally not inherited
in such cases.
--
- If no arguments follow this option, then the positional parameters are
unset. Otherwise, the positional parameters are set to the
arguments, even if some of them begin with a `-'.
-
- Signal the end of options, cause all remaining arguments
to be assigned to the positional parameters. The `-x'
and `-v' options are turned off.
If there are no arguments, the positional parameters remain unchanged.
Using `+' rather than `-' causes these options to be
turned off. The options can also be used upon invocation of the
shell. The current set of options may be found in $-
.
The remaining N arguments are positional parameters and are
assigned, in order, to $1
, $2
, ... $N
.
The special parameter #
is set to N.
The return status is always zero unless an invalid option is supplied.
4.3.2 The Shopt Builtin
This builtin allows you to change additional shell optional behavior.
shopt
-
| shopt [-pqsu] [-o] [optname ...]
|
Toggle the values of settings controlling optional shell behavior.
The settings can be either those listed below, or, if the
`-o' option is used, those available with the `-o'
option to the set
builtin command (see section 4.3.1 The Set Builtin).
With no options, or with the `-p' option, a list of all settable
options is displayed, with an indication of whether or not each is set.
The `-p' option causes output to be displayed in a form that
may be reused as input.
Other options have the following meanings:
-s
- Enable (set) each optname.
-u
- Disable (unset) each optname.
-q
- Suppresses normal output; the return status
indicates whether the optname is set or unset.
If multiple optname arguments are given with `-q',
the return status is zero if all optnames are enabled;
non-zero otherwise.
-o
- Restricts the values of
optname to be those defined for the `-o' option to the
set
builtin (see section 4.3.1 The Set Builtin).
If either `-s' or `-u'
is used with no optname arguments, shopt
shows only
those options which are set or unset, respectively.
Unless otherwise noted, the shopt
options are disabled (off)
by default.
The return status when listing options is zero if all optnames
are enabled, non-zero otherwise. When setting or unsetting options,
the return status is zero unless an optname is not a valid shell
option.
The list of shopt
options is:
autocd
- If set, a command name that is the name of a directory is executed as if
it were the argument to the
cd
command.
This option is only used by interactive shells.
cdable_vars
- If this is set, an argument to the
cd
builtin command that
is not a directory is assumed to be the name of a variable whose
value is the directory to change to.
cdspell
- If set, minor errors in the spelling of a directory component in a
cd
command will be corrected.
The errors checked for are transposed characters,
a missing character, and a character too many.
If a correction is found, the corrected path is printed,
and the command proceeds.
This option is only used by interactive shells.
checkhash
- If this is set, Bash checks that a command found in the hash
table exists before trying to execute it. If a hashed command no
longer exists, a normal path search is performed.
checkjobs
- If set, Bash lists the status of any stopped and running jobs before
exiting an interactive shell. If any jobs are running, this causes
the exit to be deferred until a second exit is attempted without an
intervening command (see section 7. Job Control).
The shell always postpones exiting if any jobs are stopped.
checkwinsize
- If set, Bash checks the window size after each command
and, if necessary, updates the values of
LINES
and COLUMNS
.
cmdhist
- If set, Bash
attempts to save all lines of a multiple-line
command in the same history entry. This allows
easy re-editing of multi-line commands.
compat31
- If set, Bash
changes its behavior to that of version 3.1 with respect to quoted
arguments to the conditional command's `=~' operator
and with respect to locale-specific
string comparison when using the
[[
conditional command's `<' and `>' operators.
Bash versions prior to bash-4.1 use ASCII collation and strcmp(3);
bash-4.1 and later use the current locale's collation sequence and strcoll(3).
compat32
- If set, Bash
changes its behavior to that of version 3.2 with respect to locale-specific
string comparison when using the
[[
conditional command's `<' and `>' operators (see previous item).
compat40
- If set, Bash
changes its behavior to that of version 4.0 with respect to locale-specific
string comparison when using the
[[
conditional command's `<' and `>' operators (see description
of compat31
)
and the effect of interrupting a command list.
Bash versions 4.0 and later interrupt the list as if the shell received the
interrupt; previous versions continue with the next command in the list.
compat41
- If set, Bash, when in POSIX mode, treats a single quote in a double-quoted
parameter expansion as a special character. The single quotes must match
(an even number) and the characters between the single quotes are considered
quoted. This is the behavior of POSIX mode through version 4.1.
The default Bash behavior remains as in previous versions.
compat42
- If set, Bash
does not process the replacement string in the pattern substitution word
expansion using quote removal.
complete_fullquote
- If set, Bash
quotes all shell metacharacters in filenames and directory names when
performing completion.
If not set, Bash
removes metacharacters such as the dollar sign from the set of
characters that will be quoted in completed filenames
when these metacharacters appear in shell variable references in words to be
completed.
This means that dollar signs in variable names that expand to directories
will not be quoted;
however, any dollar signs appearing in filenames will not be quoted, either.
This is active only when bash is using backslashes to quote completed
filenames.
This variable is set by default, which is the default Bash behavior in
versions through 4.2.
direxpand
- If set, Bash
replaces directory names with the results of word expansion when performing
filename completion. This changes the contents of the readline editing
buffer.
If not set, Bash attempts to preserve what the user typed.
dirspell
- If set, Bash
attempts spelling correction on directory names during word completion
if the directory name initially supplied does not exist.
dotglob
- If set, Bash includes filenames beginning with a `.' in
the results of filename expansion.
execfail
- If this is set, a non-interactive shell will not exit if
it cannot execute the file specified as an argument to the
exec
builtin command. An interactive shell does not exit if exec
fails.
expand_aliases
- If set, aliases are expanded as described below under Aliases,
6.6 Aliases.
This option is enabled by default for interactive shells.
extdebug
- If set, behavior intended for use by debuggers is enabled:
-
The `-F' option to the
declare
builtin (see section 4.2 Bash Builtin Commands)
displays the source file name and line number corresponding to each function
name supplied as an argument.
-
If the command run by the
DEBUG
trap returns a non-zero value, the
next command is skipped and not executed.
-
If the command run by the
DEBUG
trap returns a value of 2, and the
shell is executing in a subroutine (a shell function or a shell script
executed by the .
or source
builtins), a call to
return
is simulated.
-
BASH_ARGC
and BASH_ARGV
are updated as described in their
descriptions (see section 5.2 Bash Variables).
-
Function tracing is enabled: command substitution, shell functions, and
subshells invoked with
( command )
inherit the
DEBUG
and RETURN
traps.
-
Error tracing is enabled: command substitution, shell functions, and
subshells invoked with
( command )
inherit the
ERR
trap.
extglob
- If set, the extended pattern matching features described above
(see section 3.5.8.1 Pattern Matching) are enabled.
extquote
- If set,
$'string'
and $"string"
quoting is
performed within ${parameter}
expansions
enclosed in double quotes. This option is enabled by default.
failglob
- If set, patterns which fail to match filenames during filename expansion
result in an expansion error.
force_fignore
- If set, the suffixes specified by the
FIGNORE
shell variable
cause words to be ignored when performing word completion even if
the ignored words are the only possible completions.
See section 5.2 Bash Variables, for a description of FIGNORE
.
This option is enabled by default.
globasciiranges
- If set, range expressions used in pattern matching bracket expressions
(see section 3.5.8.1 Pattern Matching)
behave as if in the traditional C locale when performing
comparisons. That is, the current locale's collating sequence
is not taken into account, so
`b' will not collate between `A' and `B',
and upper-case and lower-case ASCII characters will collate together.
globstar
- If set, the pattern `**' used in a filename expansion context will
match all files and zero or more directories and subdirectories.
If the pattern is followed by a `/', only directories and
subdirectories match.
gnu_errfmt
- If set, shell error messages are written in the standard GNU error
message format.
histappend
- If set, the history list is appended to the file named by the value
of the
HISTFILE
variable when the shell exits, rather than overwriting the file.
histreedit
- If set, and Readline
is being used, a user is given the opportunity to re-edit a
failed history substitution.
histverify
- If set, and Readline
is being used, the results of history substitution are not immediately
passed to the shell parser. Instead, the resulting line is loaded into
the Readline editing buffer, allowing further modification.
hostcomplete
- If set, and Readline is being used, Bash will attempt to perform
hostname completion when a word containing a `@' is being
completed (see section 8.4.6 Letting Readline Type For You). This option is enabled
by default.
huponexit
- If set, Bash will send
SIGHUP
to all jobs when an interactive
login shell exits (see section 3.7.6 Signals).
interactive_comments
- Allow a word beginning with `#'
to cause that word and all remaining characters on that
line to be ignored in an interactive shell.
This option is enabled by default.
lastpipe
- If set, and job control is not active, the shell runs the last command of
a pipeline not executed in the background in the current shell environment.
lithist
- If enabled, and the
cmdhist
option is enabled, multi-line commands are saved to the history with
embedded newlines rather than using semicolon separators where possible.
login_shell
- The shell sets this option if it is started as a login shell
(see section 6.1 Invoking Bash).
The value may not be changed.
mailwarn
- If set, and a file that Bash is checking for mail has been
accessed since the last time it was checked, the message
"The mail in mailfile has been read"
is displayed.
no_empty_cmd_completion
- If set, and Readline is being used, Bash will not attempt to search
the
PATH
for possible completions when completion is attempted
on an empty line.
nocaseglob
- If set, Bash matches filenames in a case-insensitive fashion when
performing filename expansion.
nocasematch
- If set, Bash matches patterns in a case-insensitive fashion when
performing matching while executing
case
or [[
conditional commands.
nullglob
- If set, Bash allows filename patterns which match no
files to expand to a null string, rather than themselves.
progcomp
- If set, the programmable completion facilities
(see section 8.6 Programmable Completion) are enabled.
This option is enabled by default.
promptvars
- If set, prompt strings undergo
parameter expansion, command substitution, arithmetic
expansion, and quote removal after being expanded
as described below (see section 6.9 Controlling the Prompt).
This option is enabled by default.
restricted_shell
- The shell sets this option if it is started in restricted mode
(see section 6.10 The Restricted Shell).
The value may not be changed.
This is not reset when the startup files are executed, allowing
the startup files to discover whether or not a shell is restricted.
shift_verbose
- If this is set, the
shift
builtin prints an error message when the shift count exceeds the
number of positional parameters.
sourcepath
- If set, the
source
builtin uses the value of PATH
to find the directory containing the file supplied as an argument.
This option is enabled by default.
xpg_echo
- If set, the
echo
builtin expands backslash-escape sequences
by default.
The return status when listing options is zero if all optnames
are enabled, non-zero otherwise.
When setting or unsetting options, the return status is zero unless an
optname is not a valid shell option.
4.4 Special Builtins
For historical reasons, the POSIX standard has classified
several builtin commands as special.
When Bash is executing in POSIX mode, the special builtins
differ from other builtin commands in three respects:
-
Special builtins are found before shell functions during command lookup.
-
If a special builtin returns an error status, a non-interactive shell exits.
-
Assignment statements preceding the command stay in effect in the shell
environment after the command completes.
When Bash is not executing in POSIX mode, these builtins behave no
differently than the rest of the Bash builtin commands.
The Bash POSIX mode is described in 6.11 Bash POSIX Mode.
These are the POSIX special builtins:
| break : . continue eval exec exit export readonly return set
shift trap unset
|
5. Shell Variables
This chapter describes the shell variables that Bash uses.
Bash automatically assigns default values to a number of variables.
5.1 Bourne Shell Variables
Bash uses certain shell variables in the same way as the Bourne shell.
In some cases, Bash assigns a default value to the variable.
CDPATH
-
A colon-separated list of directories used as a search path for
the
cd
builtin command.
HOME
-
The current user's home directory; the default for the
cd
builtin
command.
The value of this variable is also used by tilde expansion
(see section 3.5.2 Tilde Expansion).
IFS
-
A list of characters that separate fields; used when the shell splits
words as part of expansion.
MAIL
-
If this parameter is set to a filename or directory name
and the
MAILPATH
variable
is not set, Bash informs the user of the arrival of mail in
the specified file or Maildir-format directory.
MAILPATH
-
A colon-separated list of filenames which the shell periodically checks
for new mail.
Each list entry can specify the message that is printed when new mail
arrives in the mail file by separating the filename from the message with
a `?'.
When used in the text of the message,
$_
expands to the name of
the current mail file.
OPTARG
-
The value of the last option argument processed by the
getopts
builtin.
OPTIND
-
The index of the last option argument processed by the
getopts
builtin.
PATH
-
A colon-separated list of directories in which the shell looks for
commands.
A zero-length (null) directory name in the value of
PATH
indicates the
current directory.
A null directory name may appear as two adjacent colons, or as an initial
or trailing colon.
PS1
-
The primary prompt string. The default value is `\s-\v\$ '.
See section 6.9 Controlling the Prompt, for the complete list of escape
sequences that are expanded before
PS1
is displayed.
PS2
-
The secondary prompt string. The default value is `> '.
5.2 Bash Variables
These variables are set or used by Bash, but other shells
do not normally treat them specially.
A few variables used by Bash are described in different chapters:
variables for controlling the job control facilities
(see section 7.3 Job Control Variables).
BASH
-
The full pathname used to execute the current instance of Bash.
BASHOPTS
-
A colon-separated list of enabled shell options. Each word in
the list is a valid argument for the `-s' option to the
shopt
builtin command (see section 4.3.2 The Shopt Builtin).
The options appearing in BASHOPTS
are those reported
as `on' by `shopt'.
If this variable is in the environment when Bash
starts up, each shell option in the list will be enabled before
reading any startup files. This variable is readonly.
BASHPID
-
Expands to the process ID of the current Bash process.
This differs from
$$
under certain circumstances, such as subshells
that do not require Bash to be re-initialized.
BASH_ALIASES
-
An associative array variable whose members correspond to the internal
list of aliases as maintained by the
alias
builtin.
(see section 4.1 Bourne Shell Builtins).
Elements added to this array appear in the alias list; unsetting array
elements cause aliases to be removed from the alias list.
BASH_ARGC
-
An array variable whose values are the number of parameters in each
frame of the current bash execution call stack. The number of
parameters to the current subroutine (shell function or script executed
with
.
or source
) is at the top of the stack. When a
subroutine is executed, the number of parameters passed is pushed onto
BASH_ARGC
.
The shell sets BASH_ARGC
only when in extended debugging mode
(see 4.3.2 The Shopt Builtin
for a description of the extdebug
option to the shopt
builtin).
BASH_ARGV
-
An array variable containing all of the parameters in the current bash
execution call stack. The final parameter of the last subroutine call
is at the top of the stack; the first parameter of the initial call is
at the bottom. When a subroutine is executed, the parameters supplied
are pushed onto
BASH_ARGV
.
The shell sets BASH_ARGV
only when in extended debugging mode
(see 4.3.2 The Shopt Builtin
for a description of the extdebug
option to the shopt
builtin).
BASH_CMDS
-
An associative array variable whose members correspond to the internal
hash table of commands as maintained by the
hash
builtin
(see section 4.1 Bourne Shell Builtins).
Elements added to this array appear in the hash table; unsetting array
elements cause commands to be removed from the hash table.
BASH_COMMAND
-
The command currently being executed or about to be executed, unless the
shell is executing a command as the result of a trap,
in which case it is the command executing at the time of the trap.
BASH_COMPAT
-
The value is used to set the shell's compatibility level.
See section 4.3.2 The Shopt Builtin, for a description of the various compatibility
levels and their effects.
The value may be a decimal number (e.g., 4.2) or an integer (e.g., 42)
corresponding to the desired compatibility level.
If
BASH_COMPAT
is unset or set to the empty string, the compatibility
level is set to the default for the current version.
If BASH_COMPAT
is set to a value that is not one of the valid
compatibility levels, the shell prints an error message and sets the
compatibility level to the default for the current version.
The valid compatibility levels correspond to the compatibility options
accepted by the shopt
builtin described above (for example,
compat42 means that 4.2 and 42 are valid values).
The current version is also a valid value.
BASH_ENV
-
If this variable is set when Bash is invoked to execute a shell
script, its value is expanded and used as the name of a startup file
to read before executing the script. See section 6.2 Bash Startup Files.
BASH_EXECUTION_STRING
-
The command argument to the `-c' invocation option.
BASH_LINENO
-
An array variable whose members are the line numbers in source files
where each corresponding member of FUNCNAME was invoked.
${BASH_LINENO[$i]}
is the line number in the source file
(${BASH_SOURCE[$i+1]}
) where
${FUNCNAME[$i]}
was called (or ${BASH_LINENO[$i-1]}
if
referenced within another shell function).
Use LINENO
to obtain the current line number.
BASH_REMATCH
-
An array variable whose members are assigned by the `=~' binary
operator to the
[[
conditional command
(see section 3.2.4.2 Conditional Constructs).
The element with index 0 is the portion of the string
matching the entire regular expression.
The element with index n is the portion of the
string matching the nth parenthesized subexpression.
This variable is read-only.
BASH_SOURCE
-
An array variable whose members are the source filenames where the
corresponding shell function names in the
FUNCNAME
array
variable are defined.
The shell function ${FUNCNAME[$i]}
is defined in the file
${BASH_SOURCE[$i]}
and called from ${BASH_SOURCE[$i+1]}
BASH_SUBSHELL
-
Incremented by one within each subshell or subshell environment when
the shell begins executing in that environment.
The initial value is 0.
BASH_VERSINFO
-
A readonly array variable (see section 6.7 Arrays)
whose members hold version information for this instance of Bash.
The values assigned to the array members are as follows:
BASH_VERSINFO[0]
- The major version number (the release).
BASH_VERSINFO[1]
- The minor version number (the version).
BASH_VERSINFO[2]
- The patch level.
BASH_VERSINFO[3]
- The build version.
BASH_VERSINFO[4]
- The release status (e.g., beta1).
BASH_VERSINFO[5]
- The value of
MACHTYPE
.
BASH_VERSION
-
The version number of the current instance of Bash.
BASH_XTRACEFD
-
If set to an integer corresponding to a valid file descriptor, Bash
will write the trace output generated when `set -x'
is enabled to that file descriptor.
This allows tracing output to be separated from diagnostic and error
messages.
The file descriptor is closed when
BASH_XTRACEFD
is unset or assigned
a new value.
Unsetting BASH_XTRACEFD
or assigning it the empty string causes the
trace output to be sent to the standard error.
Note that setting BASH_XTRACEFD
to 2 (the standard error file
descriptor) and then unsetting it will result in the standard error
being closed.
CHILD_MAX
-
Set the number of exited child status values for the shell to remember.
Bash will not allow this value to be decreased below a POSIX-mandated
minimum, and there is a maximum value (currently 8192) that this may
not exceed.
The minimum value is system-dependent.
COLUMNS
-
Used by the
select
command to determine the terminal width
when printing selection lists.
Automatically set if the checkwinsize
option is enabled
(see section 4.3.2 The Shopt Builtin), or in an interactive shell upon receipt of a
SIGWINCH
.
COMP_CWORD
-
An index into
${COMP_WORDS}
of the word containing the current
cursor position.
This variable is available only in shell functions invoked by the
programmable completion facilities (see section 8.6 Programmable Completion).
COMP_LINE
-
The current command line.
This variable is available only in shell functions and external
commands invoked by the
programmable completion facilities (see section 8.6 Programmable Completion).
COMP_POINT
-
The index of the current cursor position relative to the beginning of
the current command.
If the current cursor position is at the end of the current command,
the value of this variable is equal to
${#COMP_LINE}
.
This variable is available only in shell functions and external
commands invoked by the
programmable completion facilities (see section 8.6 Programmable Completion).
COMP_TYPE
-
Set to an integer value corresponding to the type of completion attempted
that caused a completion function to be called:
TAB, for normal completion,
`?', for listing completions after successive tabs,
`!', for listing alternatives on partial word completion,
`@', to list completions if the word is not unmodified,
or
`%', for menu completion.
This variable is available only in shell functions and external
commands invoked by the
programmable completion facilities (see section 8.6 Programmable Completion).
COMP_KEY
-
The key (or final key of a key sequence) used to invoke the current
completion function.
COMP_WORDBREAKS
-
The set of characters that the Readline library treats as word
separators when performing word completion.
If
COMP_WORDBREAKS
is unset, it loses its special properties,
even if it is subsequently reset.
COMP_WORDS
-
An array variable consisting of the individual
words in the current command line.
The line is split into words as Readline would split it, using
COMP_WORDBREAKS
as described above.
This variable is available only in shell functions invoked by the
programmable completion facilities (see section 8.6 Programmable Completion).
COMPREPLY
-
An array variable from which Bash reads the possible completions
generated by a shell function invoked by the programmable completion
facility (see section 8.6 Programmable Completion).
Each array element contains one possible completion.
COPROC
-
An array variable created to hold the file descriptors
for output from and input to an unnamed coprocess (see section 3.2.5 Coprocesses).
DIRSTACK
-
An array variable containing the current contents of the directory stack.
Directories appear in the stack in the order they are displayed by the
dirs
builtin.
Assigning to members of this array variable may be used to modify
directories already in the stack, but the pushd
and popd
builtins must be used to add and remove directories.
Assignment to this variable will not change the current directory.
If DIRSTACK
is unset, it loses its special properties, even if
it is subsequently reset.
EMACS
-
If Bash finds this variable in the environment when the shell
starts with value `t', it assumes that the shell is running in an
Emacs shell buffer and disables line editing.
ENV
-
Similar to
BASH_ENV
; used when the shell is invoked in
POSIX Mode (see section 6.11 Bash POSIX Mode).
EUID
-
The numeric effective user id of the current user. This variable
is readonly.
FCEDIT
-
The editor used as a default by the `-e' option to the
fc
builtin command.
FIGNORE
-
A colon-separated list of suffixes to ignore when performing
filename completion.
A filename whose suffix matches one of the entries in
FIGNORE
is excluded from the list of matched filenames. A sample
value is `.o:~'
FUNCNAME
-
An array variable containing the names of all shell functions
currently in the execution call stack.
The element with index 0 is the name of any currently-executing
shell function.
The bottom-most element (the one with the highest index)
is
"main"
.
This variable exists only when a shell function is executing.
Assignments to FUNCNAME
have no effect and return an error status.
If FUNCNAME
is unset, it loses its special properties, even if
it is subsequently reset.
This variable can be used with BASH_LINENO
and BASH_SOURCE
.
Each element of FUNCNAME
has corresponding elements in
BASH_LINENO
and BASH_SOURCE
to describe the call stack.
For instance, ${FUNCNAME[$i]}
was called from the file
${BASH_SOURCE[$i+1]}
at line number ${BASH_LINENO[$i]}
.
The caller
builtin displays the current call stack using this
information.
FUNCNEST
-
If set to a numeric value greater than 0, defines a maximum function
nesting level. Function invocations that exceed this nesting level
will cause the current command to abort.
GLOBIGNORE
-
A colon-separated list of patterns defining the set of filenames to
be ignored by filename expansion.
If a filename matched by a filename expansion pattern also matches one
of the patterns in
GLOBIGNORE
, it is removed from the list
of matches.
GROUPS
-
An array variable containing the list of groups of which the current
user is a member.
Assignments to
GROUPS
have no effect and return an error status.
If GROUPS
is unset, it loses its special properties, even if it is
subsequently reset.
histchars
-
Up to three characters which control history expansion, quick
substitution, and tokenization (see section 9.3 History Expansion).
The first character is the
history expansion character, that is, the character which signifies the
start of a history expansion, normally `!'. The second character is the
character which signifies `quick substitution' when seen as the first
character on a line, normally `^'. The optional third character is the
character which indicates that the remainder of the line is a comment when
found as the first character of a word, usually `#'. The history
comment character causes history substitution to be skipped for the
remaining words on the line. It does not necessarily cause the shell
parser to treat the rest of the line as a comment.
HISTCMD
-
The history number, or index in the history list, of the current
command. If
HISTCMD
is unset, it loses its special properties,
even if it is subsequently reset.
HISTCONTROL
-
A colon-separated list of values controlling how commands are saved on
the history list.
If the list of values includes `ignorespace', lines which begin
with a space character are not saved in the history list.
A value of `ignoredups' causes lines which match the previous
history entry to not be saved.
A value of `ignoreboth' is shorthand for
`ignorespace' and `ignoredups'.
A value of `erasedups' causes all previous lines matching the
current line to be removed from the history list before that line
is saved.
Any value not in the above list is ignored.
If
HISTCONTROL
is unset, or does not include a valid value,
all lines read by the shell parser are saved on the history list,
subject to the value of HISTIGNORE
.
The second and subsequent lines of a multi-line compound command are
not tested, and are added to the history regardless of the value of
HISTCONTROL
.
HISTFILE
-
The name of the file to which the command history is saved. The
default value is `~/.bash_history'.
HISTFILESIZE
-
The maximum number of lines contained in the history file.
When this variable is assigned a value, the history file is truncated,
if necessary, to contain no more than that number of lines
by removing the oldest entries.
The history file is also truncated to this size after
writing it when a shell exits.
If the value is 0, the history file is truncated to zero size.
Non-numeric values and numeric values less than zero inhibit truncation.
The shell sets the default value to the value of
HISTSIZE
after reading any startup files.
HISTIGNORE
-
A colon-separated list of patterns used to decide which command
lines should be saved on the history list. Each pattern is
anchored at the beginning of the line and must match the complete
line (no implicit `*' is appended). Each pattern is tested
against the line after the checks specified by
HISTCONTROL
are applied. In addition to the normal shell pattern matching
characters, `&' matches the previous history line. `&'
may be escaped using a backslash; the backslash is removed
before attempting a match.
The second and subsequent lines of a multi-line compound command are
not tested, and are added to the history regardless of the value of
HISTIGNORE
.
HISTIGNORE
subsumes the function of HISTCONTROL
. A
pattern of `&' is identical to ignoredups
, and a
pattern of `[ ]*' is identical to ignorespace
.
Combining these two patterns, separating them with a colon,
provides the functionality of ignoreboth
.
HISTSIZE
-
The maximum number of commands to remember on the history list.
If the value is 0, commands are not saved in the history list.
Numeric values less than zero result in every command being saved
on the history list (there is no limit).
The shell sets the default value to 500 after reading any startup files.
HISTTIMEFORMAT
-
If this variable is set and not null, its value is used as a format string
for strftime to print the time stamp associated with each history
entry displayed by the
history
builtin.
If this variable is set, time stamps are written to the history file so
they may be preserved across shell sessions.
This uses the history comment character to distinguish timestamps from
other history lines.
HOSTFILE
-
Contains the name of a file in the same format as `/etc/hosts' that
should be read when the shell needs to complete a hostname.
The list of possible hostname completions may be changed while the shell
is running;
the next time hostname completion is attempted after the
value is changed, Bash adds the contents of the new file to the
existing list.
If
HOSTFILE
is set, but has no value, or does not name a readable file,
Bash attempts to read
`/etc/hosts' to obtain the list of possible hostname completions.
When HOSTFILE
is unset, the hostname list is cleared.
HOSTNAME
-
The name of the current host.
HOSTTYPE
-
A string describing the machine Bash is running on.
IGNOREEOF
-
Controls the action of the shell on receipt of an
EOF
character
as the sole input. If set, the value denotes the number
of consecutive EOF
characters that can be read as the
first character on an input line
before the shell will exit. If the variable exists but does not
have a numeric value (or has no value) then the default is 10.
If the variable does not exist, then EOF
signifies the end of
input to the shell. This is only in effect for interactive shells.
INPUTRC
-
The name of the Readline initialization file, overriding the default
of `~/.inputrc'.
LANG
-
Used to determine the locale category for any category not specifically
selected with a variable starting with
LC_
.
LC_ALL
-
This variable overrides the value of
LANG
and any other
LC_
variable specifying a locale category.
LC_COLLATE
-
This variable determines the collation order used when sorting the
results of filename expansion, and
determines the behavior of range expressions, equivalence classes,
and collating sequences within filename expansion and pattern matching
(see section 3.5.8 Filename Expansion).
LC_CTYPE
-
This variable determines the interpretation of characters and the
behavior of character classes within filename expansion and pattern
matching (see section 3.5.8 Filename Expansion).
LC_MESSAGES
-
This variable determines the locale used to translate double-quoted
strings preceded by a `$' (see section 3.1.2.5 Locale-Specific Translation).
LC_NUMERIC
-
This variable determines the locale category used for number formatting.
LINENO
-
The line number in the script or shell function currently executing.
LINES
-
Used by the
select
command to determine the column length
for printing selection lists.
Automatically set if the checkwinsize
option is enabled
(see section 4.3.2 The Shopt Builtin), or in an interactive shell upon receipt of a
SIGWINCH
.
MACHTYPE
-
A string that fully describes the system type on which Bash
is executing, in the standard GNU cpu-company-system format.
MAILCHECK
-
How often (in seconds) that the shell should check for mail in the
files specified in the
MAILPATH
or MAIL
variables.
The default is 60 seconds. When it is time to check
for mail, the shell does so before displaying the primary prompt.
If this variable is unset, or set to a value that is not a number
greater than or equal to zero, the shell disables mail checking.
MAPFILE
-
An array variable created to hold the text read by the
mapfile
builtin when no variable name is supplied.
OLDPWD
-
The previous working directory as set by the
cd
builtin.
OPTERR
-
If set to the value 1, Bash displays error messages
generated by the
getopts
builtin command.
OSTYPE
-
A string describing the operating system Bash is running on.
PIPESTATUS
-
An array variable (see section 6.7 Arrays)
containing a list of exit status values from the processes
in the most-recently-executed foreground pipeline (which may
contain only a single command).
POSIXLY_CORRECT
-
If this variable is in the environment when Bash starts, the shell
enters POSIX mode (see section 6.11 Bash POSIX Mode) before reading the
startup files, as if the `--posix' invocation option had been supplied.
If it is set while the shell is running, Bash enables POSIX mode,
as if the command
had been executed.
PPID
-
The process ID of the shell's parent process. This variable
is readonly.
PROMPT_COMMAND
-
If set, the value is interpreted as a command to execute
before the printing of each primary prompt (
$PS1
).
PROMPT_DIRTRIM
-
If set to a number greater than zero, the value is used as the number of
trailing directory components to retain when expanding the
\w
and
\W
prompt string escapes (see section 6.9 Controlling the Prompt).
Characters removed are replaced with an ellipsis.
PS3
-
The value of this variable is used as the prompt for the
select
command. If this variable is not set, the
select
command prompts with `#? '
PS4
-
The value is the prompt printed before the command line is echoed
when the `-x' option is set (see section 4.3.1 The Set Builtin).
The first character of
PS4
is replicated multiple times, as
necessary, to indicate multiple levels of indirection.
The default is `+ '.
PWD
-
The current working directory as set by the
cd
builtin.
RANDOM
-
Each time this parameter is referenced, a random integer
between 0 and 32767 is generated. Assigning a value to this
variable seeds the random number generator.
READLINE_LINE
-
The contents of the Readline line buffer, for use
with `bind -x' (see section 4.2 Bash Builtin Commands).
READLINE_POINT
-
The position of the insertion point in the Readline line buffer, for use
with `bind -x' (see section 4.2 Bash Builtin Commands).
REPLY
-
The default variable for the
read
builtin.
SECONDS
-
This variable expands to the number of seconds since the
shell was started. Assignment to this variable resets
the count to the value assigned, and the expanded value
becomes the value assigned plus the number of seconds
since the assignment.
SHELL
-
The full pathname to the shell is kept in this environment variable.
If it is not set when the shell starts,
Bash assigns to it the full pathname of the current user's login shell.
SHELLOPTS
-
A colon-separated list of enabled shell options. Each word in
the list is a valid argument for the `-o' option to the
set
builtin command (see section 4.3.1 The Set Builtin).
The options appearing in SHELLOPTS
are those reported
as `on' by `set -o'.
If this variable is in the environment when Bash
starts up, each shell option in the list will be enabled before
reading any startup files. This variable is readonly.
SHLVL
-
Incremented by one each time a new instance of Bash is started. This is
intended to be a count of how deeply your Bash shells are nested.
TIMEFORMAT
-
The value of this parameter is used as a format string specifying
how the timing information for pipelines prefixed with the
time
reserved word should be displayed.
The `%' character introduces an
escape sequence that is expanded to a time value or other
information.
The escape sequences and their meanings are as
follows; the braces denote optional portions.
%%
- A literal `%'.
%[p][l]R
- The elapsed time in seconds.
%[p][l]U
- The number of CPU seconds spent in user mode.
%[p][l]S
- The number of CPU seconds spent in system mode.
%P
- The CPU percentage, computed as (%U + %S) / %R.
The optional p is a digit specifying the precision, the number of
fractional digits after a decimal point.
A value of 0 causes no decimal point or fraction to be output.
At most three places after the decimal point may be specified; values
of p greater than 3 are changed to 3.
If p is not specified, the value 3 is used.
The optional l
specifies a longer format, including minutes, of
the form MMmSS.FFs.
The value of p determines whether or not the fraction is included.
If this variable is not set, Bash acts as if it had the value
| $'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS'
|
If the value is null, no timing information is displayed.
A trailing newline is added when the format string is displayed.
TMOUT
-
If set to a value greater than zero,
TMOUT
is treated as the
default timeout for the read
builtin (see section 4.2 Bash Builtin Commands).
The select
command (see section 3.2.4.2 Conditional Constructs) terminates
if input does not arrive after TMOUT
seconds when input is coming
from a terminal.
In an interactive shell, the value is interpreted as
the number of seconds to wait for a line of input after issuing
the primary prompt.
Bash
terminates after waiting for that number of seconds if a complete
line of input does not arrive.
TMPDIR
-
If set, Bash uses its value as the name of a directory in which
Bash creates temporary files for the shell's use.
UID
-
The numeric real user id of the current user. This variable is readonly.
6. Bash Features
This chapter describes features unique to Bash.
6.1 Invoking Bash
| bash [long-opt] [-ir] [-abefhkmnptuvxdBCDHP] [-o option] [-O shopt_option] [argument ...]
bash [long-opt] [-abefhkmnptuvxdBCDHP] [-o option] [-O shopt_option] -c string [argument ...]
bash [long-opt] -s [-abefhkmnptuvxdBCDHP] [-o option] [-O shopt_option] [argument ...]
|
All of the single-character options used with the set
builtin
(see section 4.3.1 The Set Builtin) can be used as options when the shell is invoked.
In addition, there are several multi-character
options that you can use. These options must appear on the command
line before the single-character options to be recognized.
--debugger
- Arrange for the debugger profile to be executed before the shell
starts. Turns on extended debugging mode (see 4.3.2 The Shopt Builtin
for a description of the
extdebug
option to the shopt
builtin).
--dump-po-strings
- A list of all double-quoted strings preceded by `$'
is printed on the standard output
in the GNU
gettext
PO (portable object) file format.
Equivalent to `-D' except for the output format.
--dump-strings
- Equivalent to `-D'.
--help
- Display a usage message on standard output and exit successfully.
--init-file filename
--rcfile filename
- Execute commands from filename (instead of `~/.bashrc')
in an interactive shell.
--login
- Equivalent to `-l'.
--noediting
- Do not use the GNU Readline library (see section 8. Command Line Editing)
to read command lines when the shell is interactive.
--noprofile
- Don't load the system-wide startup file `/etc/profile'
or any of the personal initialization files
`~/.bash_profile', `~/.bash_login', or `~/.profile'
when Bash is invoked as a login shell.
--norc
- Don't read the `~/.bashrc' initialization file in an
interactive shell. This is on by default if the shell is
invoked as
sh
.
--posix
- Change the behavior of Bash where the default operation differs
from the POSIX standard to match the standard. This
is intended to make Bash behave as a strict superset of that
standard. See section 6.11 Bash POSIX Mode, for a description of the Bash
POSIX mode.
--restricted
- Make the shell a restricted shell (see section 6.10 The Restricted Shell).
--verbose
- Equivalent to `-v'. Print shell input lines as they're read.
--version
- Show version information for this instance of
Bash on the standard output and exit successfully.
There are several single-character options that may be supplied at
invocation which are not available with the set
builtin.
-c
- Read and execute commands from the first non-option argument
after processing the options, then exit.
Any remaining arguments are assigned to the
positional parameters, starting with
$0
.
-i
- Force the shell to run interactively. Interactive shells are
described in 6.3 Interactive Shells.
-l
- Make this shell act as if it had been directly invoked by login.
When the shell is interactive, this is equivalent to starting a
login shell with `exec -l bash'.
When the shell is not interactive, the login shell startup files will
be executed.
`exec bash -l' or `exec bash --login'
will replace the current shell with a Bash login shell.
See section 6.2 Bash Startup Files, for a description of the special behavior
of a login shell.
-r
- Make the shell a restricted shell (see section 6.10 The Restricted Shell).
-s
- If this option is present, or if no arguments remain after option
processing, then commands are read from the standard input.
This option allows the positional parameters to be set
when invoking an interactive shell.
-D
- A list of all double-quoted strings preceded by `$'
is printed on the standard output.
These are the strings that
are subject to language translation when the current locale
is not
C
or POSIX
(see section 3.1.2.5 Locale-Specific Translation).
This implies the `-n' option; no commands will be executed.
[-+]O [shopt_option]
- shopt_option is one of the shell options accepted by the
shopt
builtin (see section 4.3.2 The Shopt Builtin).
If shopt_option is present, `-O' sets the value of that option;
`+O' unsets it.
If shopt_option is not supplied, the names and values of the shell
options accepted by shopt
are printed on the standard output.
If the invocation option is `+O', the output is displayed in a format
that may be reused as input.
--
- A
--
signals the end of options and disables further option
processing.
Any arguments after the --
are treated as filenames and arguments.
A login shell is one whose first character of argument zero is
`-', or one invoked with the `--login' option.
An interactive shell is one started without non-option arguments,
unless `-s' is specified,
without specifying the `-c' option, and whose input and output are both
connected to terminals (as determined by isatty(3)
), or one
started with the `-i' option. See section 6.3 Interactive Shells, for more
information.
If arguments remain after option processing, and neither the
`-c' nor the `-s'
option has been supplied, the first argument is assumed to
be the name of a file containing shell commands (see section 3.8 Shell Scripts).
When Bash is invoked in this fashion, $0
is set to the name of the file, and the positional parameters
are set to the remaining arguments.
Bash reads and executes commands from this file, then exits.
Bash's exit status is the exit status of the last command executed
in the script. If no commands are executed, the exit status is 0.
6.2 Bash Startup Files
This section describes how Bash executes its startup files.
If any of the files exist but cannot be read, Bash reports an error.
Tildes are expanded in filenames as described above under
Tilde Expansion (see section 3.5.2 Tilde Expansion).
Interactive shells are described in 6.3 Interactive Shells.
Invoked as an interactive login shell, or with `--login'
When Bash is invoked as an interactive login shell, or as a
non-interactive shell with the `--login' option, it first reads and
executes commands from the file `/etc/profile', if that file exists.
After reading that file, it looks for `~/.bash_profile',
`~/.bash_login', and `~/.profile', in that order, and reads
and executes commands from the first one that exists and is readable.
The `--noprofile' option may be used when the shell is started to
inhibit this behavior.
When a login shell exits, Bash reads and executes commands from
the file `~/.bash_logout', if it exists.
Invoked as an interactive non-login shell
When an interactive shell that is not a login shell is started, Bash
reads and executes commands from `~/.bashrc', if that file exists.
This may be inhibited by using the `--norc' option.
The `--rcfile file' option will force Bash to read and
execute commands from file instead of `~/.bashrc'.
So, typically, your `~/.bash_profile' contains the line
| if [ -f ~/.bashrc ]; then . ~/.bashrc; fi
|
after (or before) any login-specific initializations.
Invoked non-interactively
When Bash is started non-interactively, to run a shell script,
for example, it looks for the variable BASH_ENV
in the environment,
expands its value if it appears there, and uses the expanded value as
the name of a file to read and execute. Bash behaves as if the
following command were executed:
| if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
|
but the value of the PATH
variable is not used to search for the
filename.
As noted above, if a non-interactive shell is invoked with the
`--login' option, Bash attempts to read and execute commands from the
login shell startup files.
Invoked with name sh
If Bash is invoked with the name sh
, it tries to mimic the
startup behavior of historical versions of sh
as closely as
possible, while conforming to the POSIX standard as well.
When invoked as an interactive login shell, or as a non-interactive
shell with the `--login' option, it first attempts to read
and execute commands from `/etc/profile' and `~/.profile', in
that order.
The `--noprofile' option may be used to inhibit this behavior.
When invoked as an interactive shell with the name sh
, Bash
looks for the variable ENV
, expands its value if it is defined,
and uses the expanded value as the name of a file to read and execute.
Since a shell invoked as sh
does not attempt to read and execute
commands from any other startup files, the `--rcfile' option has
no effect.
A non-interactive shell invoked with the name sh
does not attempt
to read any other startup files.
When invoked as sh
, Bash enters POSIX mode after
the startup files are read.
Invoked in POSIX mode
When Bash is started in POSIX mode, as with the
`--posix' command line option, it follows the POSIX standard
for startup files.
In this mode, interactive shells expand the ENV
variable
and commands are read and executed from the file whose name is the
expanded value.
No other startup files are read.
Invoked by remote shell daemon
Bash attempts to determine when it is being run with its standard input
connected to a network connection, as when executed by the remote shell
daemon, usually rshd
, or the secure shell daemon sshd
.
If Bash determines it is being run in
this fashion, it reads and executes commands from `~/.bashrc', if that
file exists and is readable.
It will not do this if invoked as sh
.
The `--norc' option may be used to inhibit this behavior, and the
`--rcfile' option may be used to force another file to be read, but
neither rshd
nor sshd
generally invoke the shell with those
options or allow them to be specified.
Invoked with unequal effective and real UID/GIDs
If Bash is started with the effective user (group) id not equal to the
real user (group) id, and the `-p' option is not supplied, no startup
files are read, shell functions are not inherited from the environment,
the SHELLOPTS
, BASHOPTS
, CDPATH
, and GLOBIGNORE
variables, if they appear in the environment, are ignored, and the effective
user id is set to the real user id.
If the `-p' option is supplied at invocation, the startup behavior is
the same, but the effective user id is not reset.
6.3 Interactive Shells
6.3.1 What is an Interactive Shell?
An interactive shell
is one started without non-option arguments, unless `-s' is
specified, without specifying the `-c' option, and
whose input and error output are both
connected to terminals (as determined by isatty(3)
),
or one started with the `-i' option.
An interactive shell generally reads from and writes to a user's
terminal.
The `-s' invocation option may be used to set the positional parameters
when an interactive shell is started.
6.3.2 Is this Shell Interactive?
To determine within a startup script whether or not Bash is
running interactively,
test the value of the `-' special parameter.
It contains i
when the shell is interactive. For example:
| case "$-" in
*i*) echo This shell is interactive ;;
*) echo This shell is not interactive ;;
esac
|
Alternatively, startup scripts may examine the variable
PS1
; it is unset in non-interactive shells, and set in
interactive shells. Thus:
| if [ -z "$PS1" ]; then
echo This shell is not interactive
else
echo This shell is interactive
fi
|
6.3.3 Interactive Shell Behavior
When the shell is running interactively, it changes its behavior in
several ways.
-
Startup files are read and executed as described in 6.2 Bash Startup Files.
-
Job Control (see section 7. Job Control) is enabled by default. When job
control is in effect, Bash ignores the keyboard-generated job control
signals
SIGTTIN
, SIGTTOU
, and SIGTSTP
.
-
Bash expands and displays
PS1
before reading the first line
of a command, and expands and displays PS2
before reading the
second and subsequent lines of a multi-line command.
-
Bash executes the value of the
PROMPT_COMMAND
variable as a command
before printing the primary prompt, $PS1
(see section 5.2 Bash Variables).
-
Readline (see section 8. Command Line Editing) is used to read commands from
the user's terminal.
-
Bash inspects the value of the
ignoreeof
option to set -o
instead of exiting immediately when it receives an EOF
on its
standard input when reading a command (see section 4.3.1 The Set Builtin).
-
Command history (see section 9.1 Bash History Facilities)
and history expansion (see section 9.3 History Expansion)
are enabled by default.
Bash will save the command history to the file named by
$HISTFILE
when a shell with history enabled exits.
-
Alias expansion (see section 6.6 Aliases) is performed by default.
-
In the absence of any traps, Bash ignores
SIGTERM
(see section 3.7.6 Signals).
-
In the absence of any traps,
SIGINT
is caught and handled
((see section 3.7.6 Signals).
SIGINT
will interrupt some shell builtins.
-
An interactive login shell sends a
SIGHUP
to all jobs on exit
if the huponexit
shell option has been enabled (see section 3.7.6 Signals).
-
The `-n' invocation option is ignored, and `set -n' has
no effect (see section 4.3.1 The Set Builtin).
-
Bash will check for mail periodically, depending on the values of the
MAIL
, MAILPATH
, and MAILCHECK
shell variables
(see section 5.2 Bash Variables).
-
Expansion errors due to references to unbound shell variables after
`set -u' has been enabled will not cause the shell to exit
(see section 4.3.1 The Set Builtin).
-
The shell will not exit on expansion errors caused by var being unset
or null in
${var:?word}
expansions
(see section 3.5.3 Shell Parameter Expansion).
-
Redirection errors encountered by shell builtins will not cause the
shell to exit.
-
When running in POSIX mode, a special builtin returning an error
status will not cause the shell to exit (see section 6.11 Bash POSIX Mode).
-
A failed
exec
will not cause the shell to exit
(see section 4.1 Bourne Shell Builtins).
-
Parser syntax errors will not cause the shell to exit.
-
Simple spelling correction for directory arguments to the
cd
builtin is enabled by default (see the description of the cdspell
option to the shopt
builtin in 4.3.2 The Shopt Builtin).
-
The shell will check the value of the
TMOUT
variable and exit
if a command is not read within the specified number of seconds after
printing $PS1
(see section 5.2 Bash Variables).
6.4 Bash Conditional Expressions
Conditional expressions are used by the [[
compound command
and the test
and [
builtin commands.
Expressions may be unary or binary.
Unary expressions are often used to examine the status of a file.
There are string operators and numeric comparison operators as well.
If the file argument to one of the primaries is of the form
`/dev/fd/N', then file descriptor N is checked.
If the file argument to one of the primaries is one of
`/dev/stdin', `/dev/stdout', or `/dev/stderr', file
descriptor 0, 1, or 2, respectively, is checked.
When used with [[
, the `<' and `>' operators sort
lexicographically using the current locale.
The test
command uses ASCII ordering.
Unless otherwise specified, primaries that operate on files follow symbolic
links and operate on the target of the link, rather than the link itself.
-a file
- True if file exists.
-b file
- True if file exists and is a block special file.
-c file
- True if file exists and is a character special file.
-d file
- True if file exists and is a directory.
-e file
- True if file exists.
-f file
- True if file exists and is a regular file.
-g file
- True if file exists and its set-group-id bit is set.
-h file
- True if file exists and is a symbolic link.
-k file
- True if file exists and its "sticky" bit is set.
-p file
- True if file exists and is a named pipe (FIFO).
-r file
- True if file exists and is readable.
-s file
- True if file exists and has a size greater than zero.
-t fd
- True if file descriptor fd is open and refers to a terminal.
-u file
- True if file exists and its set-user-id bit is set.
-w file
- True if file exists and is writable.
-x file
- True if file exists and is executable.
-G file
- True if file exists and is owned by the effective group id.
-L file
- True if file exists and is a symbolic link.
-N file
- True if file exists and has been modified since it was last read.
-O file
- True if file exists and is owned by the effective user id.
-S file
- True if file exists and is a socket.
file1 -ef file2
- True if file1 and file2 refer to the same device and
inode numbers.
file1 -nt file2
- True if file1 is newer (according to modification date)
than file2, or if file1 exists and file2 does not.
file1 -ot file2
- True if file1 is older than file2,
or if file2 exists and file1 does not.
-o optname
- True if the shell option optname is enabled.
The list of options appears in the description of the `-o'
option to the
set
builtin (see section 4.3.1 The Set Builtin).
-v varname
- True if the shell variable varname is set (has been assigned a value).
-R varname
- True if the shell variable varname is set and is a name reference.
-z string
- True if the length of string is zero.
-n string
string
- True if the length of string is non-zero.
string1 == string2
string1 = string2
- True if the strings are equal.
When used with the
[[
command, this performs pattern matching as
described above (see section 3.2.4.2 Conditional Constructs).
`=' should be used with the test
command for POSIX conformance.
string1 != string2
- True if the strings are not equal.
string1 < string2
- True if string1 sorts before string2 lexicographically.
string1 > string2
- True if string1 sorts after string2 lexicographically.
arg1 OP arg2
OP
is one of
`-eq', `-ne', `-lt', `-le', `-gt', or `-ge'.
These arithmetic binary operators return true if arg1
is equal to, not equal to, less than, less than or equal to,
greater than, or greater than or equal to arg2,
respectively. Arg1 and arg2
may be positive or negative integers.
6.5 Shell Arithmetic
The shell allows arithmetic expressions to be evaluated, as one of
the shell expansions or by the let
and the `-i' option
to the declare
builtins.
Evaluation is done in fixed-width integers with no check for overflow,
though division by 0 is trapped and flagged as an error.
The operators and their precedence, associativity, and values
are the same as in the C language.
The following list of operators is grouped into levels of
equal-precedence operators.
The levels are listed in order of decreasing precedence.
id++ id--
- variable post-increment and post-decrement
++id --id
- variable pre-increment and pre-decrement
- +
- unary minus and plus
! ~
- logical and bitwise negation
**
- exponentiation
* / %
- multiplication, division, remainder
+ -
- addition, subtraction
<< >>
- left and right bitwise shifts
<= >= < >
- comparison
== !=
- equality and inequality
&
- bitwise AND
^
- bitwise exclusive OR
|
- bitwise OR
&&
- logical AND
||
- logical OR
expr ? expr : expr
- conditional operator
= *= /= %= += -= <<= >>= &= ^= |=
- assignment
expr1 , expr2
- comma
Shell variables are allowed as operands; parameter expansion is
performed before the expression is evaluated.
Within an expression, shell variables may also be referenced by name
without using the parameter expansion syntax.
A shell variable that is null or unset evaluates to 0 when referenced
by name without using the parameter expansion syntax.
The value of a variable is evaluated as an arithmetic expression
when it is referenced, or when a variable which has been given the
integer attribute using `declare -i' is assigned a value.
A null value evaluates to 0.
A shell variable need not have its integer attribute turned on
to be used in an expression.
Constants with a leading 0 are interpreted as octal numbers.
A leading `0x' or `0X' denotes hexadecimal. Otherwise,
numbers take the form [base#
]n, where the optional base
is a decimal number between 2 and 64 representing the arithmetic
base, and n is a number in that base.
If base#
is omitted, then base 10 is used.
When specifying n,
he digits greater than 9 are represented by the lowercase letters,
the uppercase letters, `@', and `_', in that order.
If base is less than or equal to 36, lowercase and uppercase
letters may be used interchangeably to represent numbers between 10
and 35.
Operators are evaluated in order of precedence. Sub-expressions in
parentheses are evaluated first and may override the precedence
rules above.
6.6 Aliases
Aliases allow a string to be substituted for a word when it is used
as the first word of a simple command.
The shell maintains a list of aliases that may be set and unset with
the alias
and unalias
builtin commands.
The first word of each simple command, if unquoted, is checked to see
if it has an alias.
If so, that word is replaced by the text of the alias.
The characters `/', `$', ``', `=' and any of the
shell metacharacters or quoting characters listed above may not appear
in an alias name.
The replacement text may contain any valid
shell input, including shell metacharacters.
The first word of the replacement text is tested for
aliases, but a word that is identical to an alias being expanded
is not expanded a second time.
This means that one may alias ls
to "ls -F"
,
for instance, and Bash does not try to recursively expand the
replacement text.
If the last character of the alias value is a
blank, then the next command word following the
alias is also checked for alias expansion.
Aliases are created and listed with the alias
command, and removed with the unalias
command.
There is no mechanism for using arguments in the replacement text,
as in csh
.
If arguments are needed, a shell function should be used
(see section 3.3 Shell Functions).
Aliases are not expanded when the shell is not interactive,
unless the expand_aliases
shell option is set using
shopt
(see section 4.3.2 The Shopt Builtin).
The rules concerning the definition and use of aliases are
somewhat confusing. Bash
always reads at least one complete line
of input before executing any
of the commands on that line. Aliases are expanded when a
command is read, not when it is executed. Therefore, an
alias definition appearing on the same line as another
command does not take effect until the next line of input is read.
The commands following the alias definition
on that line are not affected by the new alias.
This behavior is also an issue when functions are executed.
Aliases are expanded when a function definition is read,
not when the function is executed, because a function definition
is itself a compound command. As a consequence, aliases
defined in a function are not available until after that
function is executed. To be safe, always put
alias definitions on a separate line, and do not use alias
in compound commands.
For almost every purpose, shell functions are preferred over aliases.
6.7 Arrays
Bash provides one-dimensional indexed and associative array variables.
Any variable may be used as an indexed array;
the declare
builtin will explicitly declare an array.
There is no maximum
limit on the size of an array, nor any requirement that members
be indexed or assigned contiguously.
Indexed arrays are referenced using integers (including arithmetic
expressions (see section 6.5 Shell Arithmetic)) and are zero-based;
associative arrays use arbitrary strings.
Unless otherwise noted, indexed array indices must be non-negative integers.
An indexed array is created automatically if any variable is assigned to
using the syntax
The subscript
is treated as an arithmetic expression that must evaluate to a number.
To explicitly declare an array, use
The syntax
| declare -a name[subscript]
|
is also accepted; the subscript is ignored.
Associative arrays are created using
Attributes may be
specified for an array variable using the declare
and
readonly
builtins. Each attribute applies to all members of
an array.
Arrays are assigned to using compound assignments of the form
| name=(value1 value2 ... )
|
where each
value is of the form [subscript]=
string.
Indexed array assignments do not require anything but string.
When assigning to indexed arrays, if
the optional subscript is supplied, that index is assigned to;
otherwise the index of the element assigned is the last index assigned
to by the statement plus one. Indexing starts at zero.
When assigning to an associative array, the subscript is required.
This syntax is also accepted by the declare
builtin. Individual array elements may be assigned to using the
name[subscript]=value
syntax introduced above.
When assigning to an indexed array, if name
is subscripted by a negative number, that number is
interpreted as relative to one greater than the maximum index of
name, so negative indices count back from the end of the
array, and an index of -1 references the last element.
Any element of an array may be referenced using
${name[subscript]}
.
The braces are required to avoid
conflicts with the shell's filename expansion operators. If the
subscript is `@' or `*', the word expands to all members
of the array name. These subscripts differ only when the word
appears within double quotes.
If the word is double-quoted,
${name[*]}
expands to a single word with
the value of each array member separated by the first character of the
IFS
variable, and ${name[@]}
expands each element of
name to a separate word. When there are no array members,
${name[@]}
expands to nothing.
If the double-quoted expansion occurs within a word, the expansion of
the first parameter is joined with the beginning part of the original
word, and the expansion of the last parameter is joined with the last
part of the original word.
This is analogous to the
expansion of the special parameters `@' and `*'.
${#name[subscript]}
expands to the length of
${name[subscript]}
.
If subscript is `@' or
`*', the expansion is the number of elements in the array.
Referencing an array variable without a subscript is equivalent to
referencing with a subscript of 0.
If the subscript
used to reference an element of an indexed array
evaluates to a number less than zero, it is
interpreted as relative to one greater than the maximum index of the array,
so negative indices count back from the end of the array,
and an index of -1 refers to the last element.
An array variable is considered set if a subscript has been assigned a
value. The null string is a valid value.
It is possible to obtain the keys (indices) of an array as well as the values.
${!name[@]} and ${!name[*]} expand to the indices
assigned in array variable name.
The treatment when in double quotes is similar to the expansion of the
special parameters `@' and `*' within double quotes.
The unset
builtin is used to destroy arrays.
unset name[subscript]
destroys the array element at index subscript.
Negative subscripts to indexed arrays are interpreted as described above.
Care must be taken to avoid unwanted side effects caused by filename
expansion.
unset name
, where name is an array, removes the
entire array. A subscript of `*' or `@' also removes the
entire array.
The declare
, local
, and readonly
builtins each accept a `-a' option to specify an indexed
array and a `-A' option to specify an associative array.
If both options are supplied, `-A' takes precedence.
The read
builtin accepts a `-a'
option to assign a list of words read from the standard input
to an array, and can read values from the standard input into
individual array elements. The set
and declare
builtins display array values in a way that allows them to be
reused as input.
6.8 The Directory Stack
The directory stack is a list of recently-visited directories. The
pushd
builtin adds directories to the stack as it changes
the current directory, and the popd
builtin removes specified
directories from the stack and changes the current directory to
the directory removed. The dirs
builtin displays the contents
of the directory stack.
The contents of the directory stack are also visible
as the value of the DIRSTACK
shell variable.
6.8.1 Directory Stack Builtins
dirs
-
Display the list of currently remembered directories. Directories
are added to the list with the pushd
command; the
popd
command removes directories from the list.
-c
- Clears the directory stack by deleting all of the elements.
-l
- Produces a listing using full pathnames;
the default listing format uses a tilde to denote the home directory.
-p
- Causes
dirs
to print the directory stack with one entry per
line.
-v
- Causes
dirs
to print the directory stack with one entry per
line, prefixing each entry with its index in the stack.
+N
- Displays the Nth directory (counting from the left of the
list printed by
dirs
when invoked without options), starting
with zero.
-N
- Displays the Nth directory (counting from the right of the
list printed by
dirs
when invoked without options), starting
with zero.
popd
-
Remove the top entry from the directory stack, and cd
to the new top directory.
When no arguments are given, popd
removes the top directory from the stack and
performs a cd
to the new top directory. The
elements are numbered from 0 starting at the first directory listed with
dirs
; that is, popd
is equivalent to popd +0
.
-n
- Suppresses the normal change of directory when removing directories
from the stack, so that only the stack is manipulated.
+N
- Removes the Nth directory (counting from the left of the
list printed by
dirs
), starting with zero.
-N
- Removes the Nth directory (counting from the right of the
list printed by
dirs
), starting with zero.
pushd
| pushd [-n] [+N | -N | dir]
|
Save the current directory on the top of the directory stack
and then cd
to dir.
With no arguments, pushd
exchanges the top two directories.
-n
- Suppresses the normal change of directory when adding directories
to the stack, so that only the stack is manipulated.
+N
- Brings the Nth directory (counting from the left of the
list printed by
dirs
, starting with zero) to the top of
the list by rotating the stack.
-N
- Brings the Nth directory (counting from the right of the
list printed by
dirs
, starting with zero) to the top of
the list by rotating the stack.
dir
- Makes the current working directory be the top of the stack, making
it the new current directory as if it had been supplied as an argument
to the
cd
builtin.
6.9 Controlling the Prompt
The value of the variable PROMPT_COMMAND
is examined just before
Bash prints each primary prompt. If PROMPT_COMMAND
is set and
has a non-null value, then the
value is executed just as if it had been typed on the command line.
In addition, the following table describes the special characters which
can appear in the prompt variables PS1
to PS4
:
\a
- A bell character.
\d
- The date, in "Weekday Month Date" format (e.g., "Tue May 26").
\D{format}
- The format is passed to
strftime
(3) and the result is inserted
into the prompt string; an empty format results in a locale-specific
time representation. The braces are required.
\e
- An escape character.
\h
- The hostname, up to the first `.'.
\H
- The hostname.
\j
- The number of jobs currently managed by the shell.
\l
- The basename of the shell's terminal device name.
\n
- A newline.
\r
- A carriage return.
\s
- The name of the shell, the basename of
$0
(the portion
following the final slash).
\t
- The time, in 24-hour HH:MM:SS format.
\T
- The time, in 12-hour HH:MM:SS format.
\@
- The time, in 12-hour am/pm format.
\A
- The time, in 24-hour HH:MM format.
\u
- The username of the current user.
\v
- The version of Bash (e.g., 2.00)
\V
- The release of Bash, version + patchlevel (e.g., 2.00.0)
\w
- The current working directory, with
$HOME
abbreviated with a tilde
(uses the $PROMPT_DIRTRIM
variable).
\W
- The basename of
$PWD
, with $HOME
abbreviated with a tilde.
\!
- The history number of this command.
\#
- The command number of this command.
\$
- If the effective uid is 0,
#
, otherwise $
.
\nnn
- The character whose ASCII code is the octal value nnn.
\\
- A backslash.
\[
- Begin a sequence of non-printing characters. This could be used to
embed a terminal control sequence into the prompt.
\]
- End a sequence of non-printing characters.
The command number and the history number are usually different:
the history number of a command is its position in the history
list, which may include commands restored from the history file
(see section 9.1 Bash History Facilities), while the command number is
the position in the sequence of commands executed during the current
shell session.
After the string is decoded, it is expanded via
parameter expansion, command substitution, arithmetic
expansion, and quote removal, subject to the value of the
promptvars
shell option (see section 4.2 Bash Builtin Commands).
6.10 The Restricted Shell
If Bash is started with the name rbash
, or the
`--restricted'
or
`-r'
option is supplied at invocation, the shell becomes restricted.
A restricted shell is used to
set up an environment more controlled than the standard shell.
A restricted shell behaves identically to bash
with the exception that the following are disallowed or not performed:
-
Changing directories with the
cd
builtin.
-
Setting or unsetting the values of the
SHELL
, PATH
,
ENV
, or BASH_ENV
variables.
-
Specifying command names containing slashes.
-
Specifying a filename containing a slash as an argument to the
.
builtin command.
-
Specifying a filename containing a slash as an argument to the `-p'
option to the
hash
builtin command.
-
Importing function definitions from the shell environment at startup.
-
Parsing the value of
SHELLOPTS
from the shell environment at startup.
-
Redirecting output using the `>', `>|', `<>', `>&',
`&>', and `>>' redirection operators.
-
Using the
exec
builtin to replace the shell with another command.
-
Adding or deleting builtin commands with the
`-f' and `-d' options to the
enable
builtin.
-
Using the
enable
builtin command to enable disabled shell builtins.
-
Specifying the `-p' option to the
command
builtin.
-
Turning off restricted mode with `set +r' or `set +o restricted'.
These restrictions are enforced after any startup files are read.
When a command that is found to be a shell script is executed
(see section 3.8 Shell Scripts), rbash
turns off any restrictions in
the shell spawned to execute the script.
6.11 Bash POSIX Mode
Starting Bash with the `--posix' command-line option or executing
`set -o posix' while Bash is running will cause Bash to conform more
closely to the POSIX standard by changing the behavior to
match that specified by POSIX in areas where the Bash default differs.
When invoked as sh
, Bash enters POSIX mode after reading the
startup files.
The following list is what's changed when `POSIX mode' is in effect:
-
When a command in the hash table no longer exists, Bash will re-search
$PATH
to find the new location. This is also available with
`shopt -s checkhash'.
-
The message printed by the job control code and builtins when a job
exits with a non-zero status is `Done(status)'.
-
The message printed by the job control code and builtins when a job
is stopped is `Stopped(signame)', where signame is, for
example,
SIGTSTP
.
-
The
bg
builtin uses the required format to describe each job placed
in the background, which does not include an indication of whether the job
is the current or previous job.
-
Reserved words appearing in a context where reserved words are recognized
do not undergo alias expansion.
-
The POSIX
PS1
and PS2
expansions of `!' to
the history number and `!!' to `!' are enabled,
and parameter expansion is performed on the values of PS1
and
PS2
regardless of the setting of the promptvars
option.
-
The POSIX startup files are executed (
$ENV
) rather than
the normal Bash files.
-
Tilde expansion is only performed on assignments preceding a command
name, rather than on all assignment statements on the line.
-
The
command
builtin does not prevent builtins that take assignment
statements as arguments from expanding them as assignment statements;
when not in POSIX mode, assignment builtins lose their assignment
statement expansion properties when preceded by command
.
-
The default history file is `~/.sh_history' (this is the
default value of
$HISTFILE
).
-
The output of `kill -l' prints all the signal names on a single line,
separated by spaces, without the `SIG' prefix.
-
The
kill
builtin does not accept signal names with a `SIG'
prefix.
-
Non-interactive shells exit if filename in
.
filename
is not found.
-
Non-interactive shells exit if a syntax error in an arithmetic expansion
results in an invalid expression.
-
Non-interactive shells exit if there is a syntax error in a script read
with the
.
or source
builtins, or in a string processed by
the eval
builtin.
-
Redirection operators do not perform filename expansion on the word
in the redirection unless the shell is interactive.
-
Redirection operators do not perform word splitting on the word in the
redirection.
-
Function names must be valid shell
name
s. That is, they may not
contain characters other than letters, digits, and underscores, and
may not start with a digit. Declaring a function with an invalid name
causes a fatal syntax error in non-interactive shells.
-
Function names may not be the same as one of the POSIX special
builtins.
-
POSIX special builtins are found before shell functions
during command lookup.
-
The
time
reserved word may be used by itself as a command. When
used in this way, it displays timing statistics for the shell and its
completed children. The TIMEFORMAT
variable controls the format
of the timing information.
-
When parsing and expanding a ${...} expansion that appears within
double quotes, single quotes are no longer special and cannot be used to
quote a closing brace or other special character, unless the operator is
one of those defined to perform pattern removal. In this case, they do
not have to appear as matched pairs.
-
The parser does not recognize
time
as a reserved word if the next
token begins with a `-'.
-
If a POSIX special builtin returns an error status, a
non-interactive shell exits. The fatal errors are those listed in
the POSIX standard, and include things like passing incorrect options,
redirection errors, variable assignment errors for assignments preceding
the command name, and so on.
-
A non-interactive shell exits with an error status if a variable
assignment error occurs when no command name follows the assignment
statements.
A variable assignment error occurs, for example, when trying to assign
a value to a readonly variable.
-
A non-interactive shell exits with an error status if a variable
assignment error occurs in an assignment statement preceding a special
builtin, but not with any other simple command.
-
A non-interactive shell exits with an error status if the iteration
variable in a
for
statement or the selection variable in a
select
statement is a readonly variable.
-
Process substitution is not available.
-
While variable indirection is available, it may not be applied to the
`#' and `?' special parameters.
-
Assignment statements preceding POSIX special builtins
persist in the shell environment after the builtin completes.
-
Assignment statements preceding shell function calls persist in the
shell environment after the function returns, as if a POSIX
special builtin command had been executed.
-
The
export
and readonly
builtin commands display their
output in the format required by POSIX.
-
The
trap
builtin displays signal names without the leading
SIG
.
-
The
trap
builtin doesn't check the first argument for a possible
signal specification and revert the signal handling to the original
disposition if it is, unless that argument consists solely of digits and
is a valid signal number. If users want to reset the handler for a given
signal to the original disposition, they should use `-' as the
first argument.
-
The
.
and source
builtins do not search the current directory
for the filename argument if it is not found by searching PATH
.
-
Subshells spawned to execute command substitutions inherit the value of
the `-e' option from the parent shell. When not in POSIX mode,
Bash clears the `-e' option in such subshells.
-
Alias expansion is always enabled, even in non-interactive shells.
-
When the
alias
builtin displays alias definitions, it does not
display them with a leading `alias ' unless the `-p' option
is supplied.
-
When the
set
builtin is invoked without options, it does not display
shell function names and definitions.
-
When the
set
builtin is invoked without options, it displays
variable values without quotes, unless they contain shell metacharacters,
even if the result contains nonprinting characters.
-
When the
cd
builtin is invoked in logical mode, and the pathname
constructed from $PWD
and the directory name supplied as an argument
does not refer to an existing directory, cd
will fail instead of
falling back to physical mode.
-
The
pwd
builtin verifies that the value it prints is the same as the
current directory, even if it is not asked to check the file system with the
`-P' option.
-
When listing the history, the
fc
builtin does not include an
indication of whether or not a history entry has been modified.
-
The default editor used by
fc
is ed
.
-
The
type
and command
builtins will not report a non-executable
file as having been found, though the shell will attempt to execute such a
file if it is the only so-named file found in $PATH
.
-
The
vi
editing mode will invoke the vi
editor directly when
the `v' command is run, instead of checking $VISUAL
and
$EDITOR
.
-
When the
xpg_echo
option is enabled, Bash does not attempt to interpret
any arguments to echo
as options. Each argument is displayed, after
escape characters are converted.
-
The
ulimit
builtin uses a block size of 512 bytes for the `-c'
and `-f' options.
-
The arrival of
SIGCHLD
when a trap is set on SIGCHLD
does
not interrupt the wait
builtin and cause it to return immediately.
The trap command is run once for each child that exits.
-
The
read
builtin may be interrupted by a signal for which a trap
has been set.
If Bash receives a trapped signal while executing read
, the trap
handler executes and read
returns an exit status greater than 128.
There is other POSIX behavior that Bash does not implement by
default even when in POSIX mode.
Specifically:
-
The
fc
builtin checks $EDITOR
as a program to edit history
entries if FCEDIT
is unset, rather than defaulting directly to
ed
. fc
uses ed
if EDITOR
is unset.
-
As noted above, Bash requires the
xpg_echo
option to be enabled for
the echo
builtin to be fully conformant.
Bash can be configured to be POSIX-conformant by default, by specifying
the `--enable-strict-posix-default' to configure
when building
(see section 10.8 Optional Features).
7. Job Control
This chapter discusses what job control is, how it works, and how
Bash allows you to access its facilities.
7.1 Job Control Basics
Job control
refers to the ability to selectively stop (suspend)
the execution of processes and continue (resume)
their execution at a later point. A user typically employs
this facility via an interactive interface supplied jointly
by the operating system kernel's terminal driver and Bash.
The shell associates a job with each pipeline. It keeps a
table of currently executing jobs, which may be listed with the
jobs
command. When Bash starts a job
asynchronously, it prints a line that looks
like:
indicating that this job is job number 1 and that the process ID
of the last process in the pipeline associated with this job is
25647. All of the processes in a single pipeline are members of
the same job. Bash uses the job abstraction as the
basis for job control.
To facilitate the implementation of the user interface to job
control, the operating system maintains the notion of a current terminal
process group ID. Members of this process group (processes whose
process group ID is equal to the current terminal process group
ID) receive keyboard-generated signals such as SIGINT
.
These processes are said to be in the foreground. Background
processes are those whose process group ID differs from the
terminal's; such processes are immune to keyboard-generated
signals. Only foreground processes are allowed to read from or, if
the user so specifies with stty tostop
, write to the terminal.
Background processes which attempt to
read from (write to when stty tostop
is in effect) the
terminal are sent a SIGTTIN
(SIGTTOU
)
signal by the kernel's terminal driver,
which, unless caught, suspends the process.
If the operating system on which Bash is running supports
job control, Bash contains facilities to use it. Typing the
suspend character (typically `^Z', Control-Z) while a
process is running causes that process to be stopped and returns
control to Bash. Typing the delayed suspend character
(typically `^Y', Control-Y) causes the process to be stopped
when it attempts to read input from the terminal, and control to
be returned to Bash. The user then manipulates the state of
this job, using the bg
command to continue it in the
background, the fg
command to continue it in the
foreground, or the kill
command to kill it. A `^Z'
takes effect immediately, and has the additional side effect of
causing pending output and typeahead to be discarded.
There are a number of ways to refer to a job in the shell. The
character `%' introduces a job specification (jobspec).
Job number n
may be referred to as `%n'.
The symbols `%%' and `%+' refer to the shell's notion of the
current job, which is the last job stopped while it was in the foreground
or started in the background.
A single `%' (with no accompanying job specification) also refers
to the current job.
The previous job may be referenced using `%-'.
If there is only a single job, `%+' and `%-' can both be used
to refer to that job.
In output pertaining to jobs (e.g., the output of the jobs
command), the current job is always flagged with a `+', and the
previous job with a `-'.
A job may also be referred to
using a prefix of the name used to start it, or using a substring
that appears in its command line. For example, `%ce' refers
to a stopped ce
job. Using `%?ce', on the
other hand, refers to any job containing the string `ce' in
its command line. If the prefix or substring matches more than one job,
Bash reports an error.
Simply naming a job can be used to bring it into the foreground:
`%1' is a synonym for `fg %1', bringing job 1 from the
background into the foreground. Similarly, `%1 &' resumes
job 1 in the background, equivalent to `bg %1'
The shell learns immediately whenever a job changes state.
Normally, Bash waits until it is about to print a prompt
before reporting changes in a job's status so as to not interrupt
any other output.
If the `-b' option to the set
builtin is enabled,
Bash reports such changes immediately (see section 4.3.1 The Set Builtin).
Any trap on SIGCHLD
is executed for each child process
that exits.
If an attempt to exit Bash is made while jobs are stopped, (or running, if
the checkjobs
option is enabled -- see 4.3.2 The Shopt Builtin), the
shell prints a warning message, and if the checkjobs
option is
enabled, lists the jobs and their statuses.
The jobs
command may then be used to inspect their status.
If a second attempt to exit is made without an intervening command,
Bash does not print another warning, and any stopped jobs are terminated.
7.2 Job Control Builtins
bg
-
Resume each suspended job jobspec in the background, as if it
had been started with `&'.
If jobspec is not supplied, the current job is used.
The return status is zero unless it is run when job control is not
enabled, or, when run with job control enabled, any
jobspec was not found or specifies a job
that was started without job control.
fg
-
Resume the job jobspec in the foreground and make it the current job.
If jobspec is not supplied, the current job is used.
The return status is that of the command placed into the foreground,
or non-zero if run when job control is disabled or, when run with
job control enabled, jobspec does not specify a valid job or
jobspec specifies a job that was started without job control.
jobs
-
| jobs [-lnprs] [jobspec]
jobs -x command [arguments]
|
The first form lists the active jobs. The options have the
following meanings:
-l
- List process IDs in addition to the normal information.
-n
- Display information only about jobs that have changed status since
the user was last notified of their status.
-p
- List only the process ID of the job's process group leader.
-r
- Display only running jobs.
-s
- Display only stopped jobs.
If jobspec is given,
output is restricted to information about that job.
If jobspec is not supplied, the status of all jobs is
listed.
If the `-x' option is supplied, jobs
replaces any
jobspec found in command or arguments with the
corresponding process group ID, and executes command,
passing it arguments, returning its exit status.
kill
-
| kill [-s sigspec] [-n signum] [-sigspec] jobspec or pid
kill -l [exit_status]
|
Send a signal specified by sigspec or signum to the process
named by job specification jobspec or process ID pid.
sigspec is either a case-insensitive signal name such as
SIGINT
(with or without the SIG
prefix)
or a signal number; signum is a signal number.
If sigspec and signum are not present, SIGTERM
is used.
The `-l' option lists the signal names.
If any arguments are supplied when `-l' is given, the names of the
signals corresponding to the arguments are listed, and the return status
is zero.
exit_status is a number specifying a signal number or the exit
status of a process terminated by a signal.
The return status is zero if at least one signal was successfully sent,
or non-zero if an error occurs or an invalid option is encountered.
wait
-
| wait [-n] [jobspec or pid ...]
|
Wait until the child process specified by each process ID pid
or job specification jobspec exits and return the exit status of the
last command waited for.
If a job spec is given, all processes in the job are waited for.
If no arguments are given, all currently active child processes are
waited for, and the return status is zero.
If the `-n' option is supplied, wait
waits for any job to
terminate and returns its exit status.
If neither jobspec nor pid specifies an active child process
of the shell, the return status is 127.
disown
-
| disown [-ar] [-h] [jobspec ...]
|
Without options, remove each jobspec from the table of
active jobs.
If the `-h' option is given, the job is not removed from the table,
but is marked so that SIGHUP
is not sent to the job if the shell
receives a SIGHUP
.
If jobspec is not present, and neither the `-a' nor the
`-r' option is supplied, the current job is used.
If no jobspec is supplied, the `-a' option means to remove or
mark all jobs; the `-r' option without a jobspec
argument restricts operation to running jobs.
suspend
-
Suspend the execution of this shell until it receives a
SIGCONT
signal.
A login shell cannot be suspended; the `-f'
option can be used to override this and force the suspension.
When job control is not active, the kill
and wait
builtins do not accept jobspec arguments. They must be
supplied process IDs.
7.3 Job Control Variables
auto_resume
-
This variable controls how the shell interacts with the user and
job control. If this variable exists then single word simple
commands without redirections are treated as candidates for resumption
of an existing job. There is no ambiguity allowed; if there is
more than one job beginning with the string typed, then
the most recently accessed job will be selected.
The name of a stopped job, in this context, is the command line
used to start it. If this variable is set to the value `exact',
the string supplied must match the name of a stopped job exactly;
if set to `substring',
the string supplied needs to match a substring of the name of a
stopped job. The `substring' value provides functionality
analogous to the `%?' job ID (see section 7.1 Job Control Basics).
If set to any other value, the supplied string must
be a prefix of a stopped job's name; this provides functionality
analogous to the `%' job ID.
8. Command Line Editing
This chapter describes the basic features of the GNU
command line editing interface.
Command line editing is provided by the Readline library, which is
used by several different programs, including Bash.
Command line editing is enabled by default when using an interactive shell,
unless the `--noediting' option is supplied at shell invocation.
Line editing is also used when using the `-e' option to the
read
builtin command (see section 4.2 Bash Builtin Commands).
By default, the line editing commands are similar to those of Emacs.
A vi-style line editing interface is also available.
Line editing can be enabled at any time using the `-o emacs' or
`-o vi' options to the set
builtin command
(see section 4.3.1 The Set Builtin), or disabled using the `+o emacs' or
`+o vi' options to set
.
8.1 Introduction to Line Editing
The following paragraphs describe the notation used to represent
keystrokes.
The text C-k is read as `Control-K' and describes the character
produced when the k key is pressed while the Control key
is depressed.
The text M-k is read as `Meta-K' and describes the character
produced when the Meta key (if you have one) is depressed, and the k
key is pressed.
The Meta key is labeled ALT on many keyboards.
On keyboards with two keys labeled ALT (usually to either side of
the space bar), the ALT on the left side is generally set to
work as a Meta key.
The ALT key on the right may also be configured to work as a
Meta key or may be configured as some other modifier, such as a
Compose key for typing accented characters.
If you do not have a Meta or ALT key, or another key working as
a Meta key, the identical keystroke can be generated by typing ESC
first, and then typing k.
Either process is known as metafying the k key.
The text M-C-k is read as `Meta-Control-k' and describes the
character produced by metafying C-k.
In addition, several keys have their own names. Specifically,
DEL, ESC, LFD, SPC, RET, and TAB all
stand for themselves when seen in this text, or in an init file
(see section 8.3 Readline Init File).
If your keyboard lacks a LFD key, typing C-j will
produce the desired character.
The RET key may be labeled Return or Enter on
some keyboards.
8.2 Readline Interaction
Often during an interactive session you type in a long line of text,
only to notice that the first word on the line is misspelled. The
Readline library gives you a set of commands for manipulating the text
as you type it in, allowing you to just fix your typo, and not forcing
you to retype the majority of the line. Using these editing commands,
you move the cursor to the place that needs correction, and delete or
insert the text of the corrections. Then, when you are satisfied with
the line, you simply press RET. You do not have to be at the
end of the line to press RET; the entire line is accepted
regardless of the location of the cursor within the line.
8.2.1 Readline Bare Essentials
In order to enter characters into the line, simply type them. The typed
character appears where the cursor was, and then the cursor moves one
space to the right. If you mistype a character, you can use your
erase character to back up and delete the mistyped character.
Sometimes you may mistype a character, and
not notice the error until you have typed several other characters. In
that case, you can type C-b to move the cursor to the left, and then
correct your mistake. Afterwards, you can move the cursor to the right
with C-f.
When you add text in the middle of a line, you will notice that characters
to the right of the cursor are `pushed over' to make room for the text
that you have inserted. Likewise, when you delete text behind the cursor,
characters to the right of the cursor are `pulled back' to fill in the
blank space created by the removal of the text. A list of the bare
essentials for editing the text of an input line follows.
- C-b
- Move back one character.
- C-f
- Move forward one character.
- DEL or Backspace
- Delete the character to the left of the cursor.
- C-d
- Delete the character underneath the cursor.
- Printing characters
- Insert the character into the line at the cursor.
- C-_ or C-x C-u
- Undo the last editing command. You can undo all the way back to an
empty line.
(Depending on your configuration, the Backspace key be set to
delete the character to the left of the cursor and the DEL key set
to delete the character underneath the cursor, like C-d, rather
than the character to the left of the cursor.)
8.2.2 Readline Movement Commands
The above table describes the most basic keystrokes that you need
in order to do editing of the input line. For your convenience, many
other commands have been added in addition to C-b, C-f,
C-d, and DEL. Here are some commands for moving more rapidly
about the line.
- C-a
- Move to the start of the line.
- C-e
- Move to the end of the line.
- M-f
- Move forward a word, where a word is composed of letters and digits.
- M-b
- Move backward a word.
- C-l
- Clear the screen, reprinting the current line at the top.
Notice how C-f moves forward a character, while M-f moves
forward a word. It is a loose convention that control keystrokes
operate on characters while meta keystrokes operate on words.
8.2.3 Readline Killing Commands
Killing text means to delete the text from the line, but to save
it away for later use, usually by yanking (re-inserting)
it back into the line.
(`Cut' and `paste' are more recent jargon for `kill' and `yank'.)
If the description for a command says that it `kills' text, then you can
be sure that you can get the text back in a different (or the same)
place later.
When you use a kill command, the text is saved in a kill-ring.
Any number of consecutive kills save all of the killed text together, so
that when you yank it back, you get it all. The kill
ring is not line specific; the text that you killed on a previously
typed line is available to be yanked back later, when you are typing
another line.
Here is the list of commands for killing text.
- C-k
- Kill the text from the current cursor position to the end of the line.
- M-d
- Kill from the cursor to the end of the current word, or, if between
words, to the end of the next word.
Word boundaries are the same as those used by M-f.
- M-DEL
- Kill from the cursor the start of the current word, or, if between
words, to the start of the previous word.
Word boundaries are the same as those used by M-b.
- C-w
- Kill from the cursor to the previous whitespace. This is different than
M-DEL because the word boundaries differ.
Here is how to yank the text back into the line. Yanking
means to copy the most-recently-killed text from the kill buffer.
- C-y
- Yank the most recently killed text back into the buffer at the cursor.
- M-y
- Rotate the kill-ring, and yank the new top. You can only do this if
the prior command is C-y or M-y.
8.2.4 Readline Arguments
You can pass numeric arguments to Readline commands. Sometimes the
argument acts as a repeat count, other times it is the sign of the
argument that is significant. If you pass a negative argument to a
command which normally acts in a forward direction, that command will
act in a backward direction. For example, to kill text back to the
start of the line, you might type `M-- C-k'.
The general way to pass numeric arguments to a command is to type meta
digits before the command. If the first `digit' typed is a minus
sign (`-'), then the sign of the argument will be negative. Once
you have typed one meta digit to get the argument started, you can type
the remainder of the digits, and then the command. For example, to give
the C-d command an argument of 10, you could type `M-1 0 C-d',
which will delete the next ten characters on the input line.
8.2.5 Searching for Commands in the History
Readline provides commands for searching through the command history
(see section 9.1 Bash History Facilities)
for lines containing a specified string.
There are two search modes: incremental and non-incremental.
Incremental searches begin before the user has finished typing the
search string.
As each character of the search string is typed, Readline displays
the next entry from the history matching the string typed so far.
An incremental search requires only as many characters as needed to
find the desired history entry.
To search backward in the history for a particular string, type
C-r. Typing C-s searches forward through the history.
The characters present in the value of the isearch-terminators
variable
are used to terminate an incremental search.
If that variable has not been assigned a value, the ESC and
C-J characters will terminate an incremental search.
C-g will abort an incremental search and restore the original line.
When the search is terminated, the history entry containing the
search string becomes the current line.
To find other matching entries in the history list, type C-r or
C-s as appropriate.
This will search backward or forward in the history for the next
entry matching the search string typed so far.
Any other key sequence bound to a Readline command will terminate
the search and execute that command.
For instance, a RET will terminate the search and accept
the line, thereby executing the command from the history list.
A movement command will terminate the search, make the last line found
the current line, and begin editing.
Readline remembers the last incremental search string. If two
C-rs are typed without any intervening characters defining a new
search string, any remembered search string is used.
Non-incremental searches read the entire search string before starting
to search for matching history lines. The search string may be
typed by the user or be part of the contents of the current line.
8.3 Readline Init File
Although the Readline library comes with a set of Emacs-like
keybindings installed by default, it is possible to use a different set
of keybindings.
Any user can customize programs that use Readline by putting
commands in an inputrc file, conventionally in his home directory.
The name of this
file is taken from the value of the shell variable INPUTRC
. If
that variable is unset, the default is `~/.inputrc'. If that
file does not exist or cannot be read, the ultimate default is
`/etc/inputrc'.
When a program which uses the Readline library starts up, the
init file is read, and the key bindings are set.
In addition, the C-x C-r
command re-reads this init file, thus
incorporating any changes that you might have made to it.
8.3.1 Readline Init File Syntax
There are only a few basic constructs allowed in the
Readline init file. Blank lines are ignored.
Lines beginning with a `#' are comments.
Lines beginning with a `$' indicate conditional
constructs (see section 8.3.2 Conditional Init Constructs). Other lines
denote variable settings and key bindings.
- Variable Settings
- You can modify the run-time behavior of Readline by
altering the values of variables in Readline
using the
set
command within the init file.
The syntax is simple:
Here, for example, is how to
change from the default Emacs-like key binding to use
vi
line editing commands:
Variable names and values, where appropriate, are recognized without regard
to case. Unrecognized variable names are ignored.
Boolean variables (those that can be set to on or off) are set to on if
the value is null or empty, on (case-insensitive), or 1. Any other
value results in the variable being set to off.
The bind -V
command lists the current Readline variable names
and values. See section 4.2 Bash Builtin Commands.
A great deal of run-time behavior is changeable with the following
variables.
bell-style
-
Controls what happens when Readline wants to ring the terminal bell.
If set to `none', Readline never rings the bell. If set to
`visible', Readline uses a visible bell if one is available.
If set to `audible' (the default), Readline attempts to ring
the terminal's bell.
bind-tty-special-chars
-
If set to `on', Readline attempts to bind the control characters
treated specially by the kernel's terminal driver to their Readline
equivalents.
colored-stats
-
If set to `on', Readline displays possible completions using different
colors to indicate their file type.
The color definitions are taken from the value of the
LS_COLORS
environment variable.
The default is `off'.
comment-begin
-
The string to insert at the beginning of the line when the
insert-comment
command is executed. The default value
is "#"
.
completion-display-width
-
The number of screen columns used to display possible matches
when performing completion.
The value is ignored if it is less than 0 or greater than the terminal
screen width.
A value of 0 will cause matches to be displayed one per line.
The default value is -1.
completion-ignore-case
-
If set to `on', Readline performs filename matching and completion
in a case-insensitive fashion.
The default value is `off'.
completion-map-case
-
If set to `on', and completion-ignore-case is enabled, Readline
treats hyphens (`-') and underscores (`_') as equivalent when
performing case-insensitive filename matching and completion.
completion-prefix-display-length
-
The length in characters of the common prefix of a list of possible
completions that is displayed without modification. When set to a
value greater than zero, common prefixes longer than this value are
replaced with an ellipsis when displaying possible completions.
completion-query-items
-
The number of possible completions that determines when the user is
asked whether the list of possibilities should be displayed.
If the number of possible completions is greater than this value,
Readline will ask the user whether or not he wishes to view
them; otherwise, they are simply listed.
This variable must be set to an integer value greater than or equal to 0.
A negative value means Readline should never ask.
The default limit is
100
.
convert-meta
-
If set to `on', Readline will convert characters with the
eighth bit set to an ASCII key sequence by stripping the eighth
bit and prefixing an ESC character, converting them to a
meta-prefixed key sequence. The default value is `on'.
disable-completion
-
If set to `On', Readline will inhibit word completion.
Completion characters will be inserted into the line as if they had
been mapped to
self-insert
. The default is `off'.
editing-mode
-
The
editing-mode
variable controls which default set of
key bindings is used. By default, Readline starts up in Emacs editing
mode, where the keystrokes are most similar to Emacs. This variable can be
set to either `emacs' or `vi'.
echo-control-characters
- When set to `on', on operating systems that indicate they support it,
readline echoes a character corresponding to a signal generated from the
keyboard. The default is `on'.
enable-keypad
-
When set to `on', Readline will try to enable the application
keypad when it is called. Some systems need this to enable the
arrow keys. The default is `off'.
enable-meta-key
- When set to `on', Readline will try to enable any meta modifier
key the terminal claims to support when it is called. On many terminals,
the meta key is used to send eight-bit characters.
The default is `on'.
expand-tilde
-
If set to `on', tilde expansion is performed when Readline
attempts word completion. The default is `off'.
history-preserve-point
-
If set to `on', the history code attempts to place the point (the
current cursor position) at the
same location on each history line retrieved with
previous-history
or next-history
. The default is `off'.
history-size
-
Set the maximum number of history entries saved in the history list.
If set to zero, any existing history entries are deleted and no new entries
are saved.
If set to a value less than zero, the number of history entries is not
limited.
By default, the number of history entries is not limited.
horizontal-scroll-mode
-
This variable can be set to either `on' or `off'. Setting it
to `on' means that the text of the lines being edited will scroll
horizontally on a single screen line when they are longer than the width
of the screen, instead of wrapping onto a new screen line. By default,
this variable is set to `off'.
input-meta
-
If set to `on', Readline will enable eight-bit input (it
will not clear the eighth bit in the characters it reads),
regardless of what the terminal claims it can support. The
default value is `off'. The name
meta-flag
is a
synonym for this variable.
isearch-terminators
-
The string of characters that should terminate an incremental search without
subsequently executing the character as a command (see section 8.2.5 Searching for Commands in the History).
If this variable has not been given a value, the characters ESC and
C-J will terminate an incremental search.
keymap
-
Sets Readline's idea of the current keymap for key binding commands.
Acceptable
keymap
names are
emacs
,
emacs-standard
,
emacs-meta
,
emacs-ctlx
,
vi
,
vi-move
,
vi-command
, and
vi-insert
.
vi
is equivalent to vi-command
; emacs
is
equivalent to emacs-standard
. The default value is emacs
.
The value of the editing-mode
variable also affects the
default keymap.
keyseq-timeout
- Specifies the duration Readline will wait for a character when reading an
ambiguous key sequence (one that can form a complete key sequence using
the input read so far, or can take additional input to complete a longer
key sequence).
If no input is received within the timeout, Readline will use the shorter
but complete key sequence.
Readline uses this value to determine whether or not input is
available on the current input source (
rl_instream
by default).
The value is specified in milliseconds, so a value of 1000 means that
Readline will wait one second for additional input.
If this variable is set to a value less than or equal to zero, or to a
non-numeric value, Readline will wait until another key is pressed to
decide which key sequence to complete.
The default value is 500
.
mark-directories
- If set to `on', completed directory names have a slash
appended. The default is `on'.
mark-modified-lines
-
This variable, when set to `on', causes Readline to display an
asterisk (`*') at the start of history lines which have been modified.
This variable is `off' by default.
mark-symlinked-directories
-
If set to `on', completed names which are symbolic links
to directories have a slash appended (subject to the value of
mark-directories
).
The default is `off'.
match-hidden-files
-
This variable, when set to `on', causes Readline to match files whose
names begin with a `.' (hidden files) when performing filename
completion.
If set to `off', the leading `.' must be
supplied by the user in the filename to be completed.
This variable is `on' by default.
menu-complete-display-prefix
-
If set to `on', menu completion displays the common prefix of the
list of possible completions (which may be empty) before cycling through
the list. The default is `off'.
output-meta
-
If set to `on', Readline will display characters with the
eighth bit set directly rather than as a meta-prefixed escape
sequence. The default is `off'.
page-completions
-
If set to `on', Readline uses an internal
more
-like pager
to display a screenful of possible completions at a time.
This variable is `on' by default.
print-completions-horizontally
- If set to `on', Readline will display completions with matches
sorted horizontally in alphabetical order, rather than down the screen.
The default is `off'.
revert-all-at-newline
-
If set to `on', Readline will undo all changes to history lines
before returning when
accept-line
is executed. By default,
history lines may be modified and retain individual undo lists across
calls to readline
. The default is `off'.
show-all-if-ambiguous
-
This alters the default behavior of the completion functions. If
set to `on',
words which have more than one possible completion cause the
matches to be listed immediately instead of ringing the bell.
The default value is `off'.
show-all-if-unmodified
-
This alters the default behavior of the completion functions in
a fashion similar to show-all-if-ambiguous.
If set to `on',
words which have more than one possible completion without any
possible partial completion (the possible completions don't share
a common prefix) cause the matches to be listed immediately instead
of ringing the bell.
The default value is `off'.
show-mode-in-prompt
-
If set to `on', add a character to the beginning of the prompt
indicating the editing mode: emacs (`@'), vi command (`:'),
or vi insertion (`+').
The default value is `off'.
skip-completed-text
-
If set to `on', this alters the default completion behavior when
inserting a single match into the line. It's only active when
performing completion in the middle of a word. If enabled, readline
does not insert characters from the completion that match characters
after point in the word being completed, so portions of the word
following the cursor are not duplicated.
For instance, if this is enabled, attempting completion when the cursor
is after the `e' in `Makefile' will result in `Makefile'
rather than `Makefilefile', assuming there is a single possible
completion.
The default value is `off'.
visible-stats
-
If set to `on', a character denoting a file's type
is appended to the filename when listing possible
completions. The default is `off'.
- Key Bindings
- The syntax for controlling key bindings in the init file is
simple. First you need to find the name of the command that you
want to change. The following sections contain tables of the command
name, the default keybinding, if any, and a short description of what
the command does.
Once you know the name of the command, simply place on a line
in the init file the name of the key
you wish to bind the command to, a colon, and then the name of the
command.
There can be no space between the key name and the colon -- that will be
interpreted as part of the key name.
The name of the key can be expressed in different ways, depending on
what you find most comfortable.
In addition to command names, readline allows keys to be bound
to a string that is inserted when the key is pressed (a macro).
The bind -p
command displays Readline function names and
bindings in a format that can put directly into an initialization file.
See section 4.2 Bash Builtin Commands.
- keyname: function-name or macro
- keyname is the name of a key spelled out in English. For example:
| Control-u: universal-argument
Meta-Rubout: backward-kill-word
Control-o: "> output"
|
In the above example, C-u is bound to the function
universal-argument
,
M-DEL is bound to the function backward-kill-word
, and
C-o is bound to run the macro
expressed on the right hand side (that is, to insert the text
`> output' into the line).
A number of symbolic character names are recognized while
processing this key binding syntax:
DEL,
ESC,
ESCAPE,
LFD,
NEWLINE,
RET,
RETURN,
RUBOUT,
SPACE,
SPC,
and
TAB.
- "keyseq": function-name or macro
- keyseq differs from keyname above in that strings
denoting an entire key sequence can be specified, by placing
the key sequence in double quotes. Some GNU Emacs style key
escapes can be used, as in the following example, but the
special character names are not recognized.
| "\C-u": universal-argument
"\C-x\C-r": re-read-init-file
"\e[11~": "Function Key 1"
|
In the above example, C-u is again bound to the function
universal-argument
(just as it was in the first example),
`C-x C-r' is bound to the function re-read-init-file
,
and `ESC [ 1 1 ~' is bound to insert
the text `Function Key 1'.
The following GNU Emacs style escape sequences are available when
specifying key sequences:
\C-
- control prefix
\M-
- meta prefix
\e
- an escape character
\\
- backslash
\"
- ", a double quotation mark
\'
- ', a single quote or apostrophe
In addition to the GNU Emacs style escape sequences, a second
set of backslash escapes is available:
\a
- alert (bell)
\b
- backspace
\d
- delete
\f
- form feed
\n
- newline
\r
- carriage return
\t
- horizontal tab
\v
- vertical tab
\nnn
- the eight-bit character whose value is the octal value nnn
(one to three digits)
\xHH
- the eight-bit character whose value is the hexadecimal value HH
(one or two hex digits)
When entering the text of a macro, single or double quotes must
be used to indicate a macro definition.
Unquoted text is assumed to be a function name.
In the macro body, the backslash escapes described above are expanded.
Backslash will quote any other character in the macro text,
including `"' and `''.
For example, the following binding will make `C-x \'
insert a single `\' into the line:
8.3.2 Conditional Init Constructs
Readline implements a facility similar in spirit to the conditional
compilation features of the C preprocessor which allows key
bindings and variable settings to be performed as the result
of tests. There are four parser directives used.
$if
- The
$if
construct allows bindings to be made based on the
editing mode, the terminal being used, or the application using
Readline. The text of the test extends to the end of the line;
no characters are required to isolate it.
mode
- The
mode=
form of the $if
directive is used to test
whether Readline is in emacs
or vi
mode.
This may be used in conjunction
with the `set keymap' command, for instance, to set bindings in
the emacs-standard
and emacs-ctlx
keymaps only if
Readline is starting out in emacs
mode.
term
- The
term=
form may be used to include terminal-specific
key bindings, perhaps to bind the key sequences output by the
terminal's function keys. The word on the right side of the
`=' is tested against both the full name of the terminal and
the portion of the terminal name before the first `-'. This
allows sun
to match both sun
and sun-cmd
,
for instance.
application
- The application construct is used to include
application-specific settings. Each program using the Readline
library sets the application name, and you can test for
a particular value.
This could be used to bind key sequences to functions useful for
a specific program. For instance, the following command adds a
key sequence that quotes the current or previous word in Bash:
| $if Bash
# Quote the current or previous word
"\C-xq": "\eb\"\ef\""
$endif
|
$endif
- This command, as seen in the previous example, terminates an
$if
command.
$else
- Commands in this branch of the
$if
directive are executed if
the test fails.
$include
- This directive takes a single filename as an argument and reads commands
and bindings from that file.
For example, the following directive reads from `/etc/inputrc':
8.3.3 Sample Init File
Here is an example of an inputrc file. This illustrates key
binding, variable assignment, and conditional syntax.
| # This file controls the behaviour of line input editing for
# programs that use the GNU Readline library. Existing
# programs include FTP, Bash, and GDB.
#
# You can re-read the inputrc file with C-x C-r.
# Lines beginning with '#' are comments.
#
# First, include any system-wide bindings and variable
# assignments from /etc/Inputrc
$include /etc/Inputrc
#
# Set various bindings for emacs mode.
set editing-mode emacs
$if mode=emacs
Meta-Control-h: backward-kill-word Text after the function name is ignored
#
# Arrow keys in keypad mode
#
#"\M-OD": backward-char
#"\M-OC": forward-char
#"\M-OA": previous-history
#"\M-OB": next-history
#
# Arrow keys in ANSI mode
#
"\M-[D": backward-char
"\M-[C": forward-char
"\M-[A": previous-history
"\M-[B": next-history
#
# Arrow keys in 8 bit keypad mode
#
#"\M-\C-OD": backward-char
#"\M-\C-OC": forward-char
#"\M-\C-OA": previous-history
#"\M-\C-OB": next-history
#
# Arrow keys in 8 bit ANSI mode
#
#"\M-\C-[D": backward-char
#"\M-\C-[C": forward-char
#"\M-\C-[A": previous-history
#"\M-\C-[B": next-history
C-q: quoted-insert
$endif
# An old-style binding. This happens to be the default.
TAB: complete
# Macros that are convenient for shell interaction
$if Bash
# edit the path
"\C-xp": "PATH=${PATH}\e\C-e\C-a\ef\C-f"
# prepare to type a quoted word --
# insert open and close double quotes
# and move to just after the open quote
"\C-x\"": "\"\"\C-b"
# insert a backslash (testing backslash escapes
# in sequences and macros)
"\C-x\\": "\\"
# Quote the current or previous word
"\C-xq": "\eb\"\ef\""
# Add a binding to refresh the line, which is unbound
"\C-xr": redraw-current-line
# Edit variable on current line.
"\M-\C-v": "\C-a\C-k$\C-y\M-\C-e\C-a\C-y="
$endif
# use a visible bell if one is available
set bell-style visible
# don't strip characters to 7 bits when reading
set input-meta on
# allow iso-latin1 characters to be inserted rather
# than converted to prefix-meta sequences
set convert-meta off
# display characters with the eighth bit set directly
# rather than as meta-prefixed characters
set output-meta on
# if there are more than 150 possible completions for
# a word, ask the user if he wants to see all of them
set completion-query-items 150
# For FTP
$if Ftp
"\C-xg": "get \M-?"
"\C-xt": "put \M-?"
"\M-.": yank-last-arg
$endif
|
8.4 Bindable Readline Commands
This section describes Readline commands that may be bound to key
sequences.
You can list your key bindings by executing
bind -P
or, for a more terse format, suitable for an
inputrc file, bind -p
. (See section 4.2 Bash Builtin Commands.)
Command names without an accompanying key sequence are unbound by default.
In the following descriptions, point refers to the current cursor
position, and mark refers to a cursor position saved by the
set-mark
command.
The text between the point and mark is referred to as the region.
8.4.1 Commands For Moving
beginning-of-line (C-a)
-
Move to the start of the current line.
end-of-line (C-e)
-
Move to the end of the line.
forward-char (C-f)
-
Move forward a character.
backward-char (C-b)
-
Move back a character.
forward-word (M-f)
-
Move forward to the end of the next word.
Words are composed of letters and digits.
backward-word (M-b)
-
Move back to the start of the current or previous word.
Words are composed of letters and digits.
shell-forward-word ()
-
Move forward to the end of the next word.
Words are delimited by non-quoted shell metacharacters.
shell-backward-word ()
-
Move back to the start of the current or previous word.
Words are delimited by non-quoted shell metacharacters.
clear-screen (C-l)
-
Clear the screen and redraw the current line,
leaving the current line at the top of the screen.
redraw-current-line ()
-
Refresh the current line. By default, this is unbound.
8.4.2 Commands For Manipulating The History
accept-line (Newline or Return)
-
Accept the line regardless of where the cursor is.
If this line is
non-empty, add it to the history list according to the setting of
the
HISTCONTROL
and HISTIGNORE
variables.
If this line is a modified history line, then restore the history line
to its original state.
previous-history (C-p)
-
Move `back' through the history list, fetching the previous command.
next-history (C-n)
-
Move `forward' through the history list, fetching the next command.
beginning-of-history (M-<)
-
Move to the first line in the history.
end-of-history (M->)
-
Move to the end of the input history, i.e., the line currently
being entered.
reverse-search-history (C-r)
-
Search backward starting at the current line and moving `up' through
the history as necessary. This is an incremental search.
forward-search-history (C-s)
-
Search forward starting at the current line and moving `down' through
the the history as necessary. This is an incremental search.
non-incremental-reverse-search-history (M-p)
-
Search backward starting at the current line and moving `up'
through the history as necessary using a non-incremental search
for a string supplied by the user.
non-incremental-forward-search-history (M-n)
-
Search forward starting at the current line and moving `down'
through the the history as necessary using a non-incremental search
for a string supplied by the user.
history-search-forward ()
-
Search forward through the history for the string of characters
between the start of the current line and the point.
The search string must match at the beginning of a history line.
This is a non-incremental search.
By default, this command is unbound.
history-search-backward ()
-
Search backward through the history for the string of characters
between the start of the current line and the point.
The search string must match at the beginning of a history line.
This is a non-incremental search.
By default, this command is unbound.
history-substr-search-forward ()
-
Search forward through the history for the string of characters
between the start of the current line and the point.
The search string may match anywhere in a history line.
This is a non-incremental search.
By default, this command is unbound.
history-substr-search-backward ()
-
Search backward through the history for the string of characters
between the start of the current line and the point.
The search string may match anywhere in a history line.
This is a non-incremental search.
By default, this command is unbound.
yank-nth-arg (M-C-y)
-
Insert the first argument to the previous command (usually
the second word on the previous line) at point.
With an argument n,
insert the nth word from the previous command (the words
in the previous command begin with word 0). A negative argument
inserts the nth word from the end of the previous command.
Once the argument n is computed, the argument is extracted
as if the `!n' history expansion had been specified.
yank-last-arg (M-. or M-_)
-
Insert last argument to the previous command (the last word of the
previous history entry).
With a numeric argument, behave exactly like
yank-nth-arg
.
Successive calls to yank-last-arg
move back through the history
list, inserting the last word (or the word specified by the argument to
the first call) of each line in turn.
Any numeric argument supplied to these successive calls determines
the direction to move through the history. A negative argument switches
the direction through the history (back or forward).
The history expansion facilities are used to extract the last argument,
as if the `!$' history expansion had been specified.
8.4.3 Commands For Changing Text
end-of-file (usually C-d)
-
The character indicating end-of-file as set, for example, by
stty
. If this character is read when there are no characters
on the line, and point is at the beginning of the line, Readline
interprets it as the end of input and returns EOF.
delete-char (C-d)
-
Delete the character at point. If this function is bound to the
same character as the tty EOF character, as C-d
commonly is, see above for the effects.
backward-delete-char (Rubout)
-
Delete the character behind the cursor. A numeric argument means
to kill the characters instead of deleting them.
forward-backward-delete-char ()
-
Delete the character under the cursor, unless the cursor is at the
end of the line, in which case the character behind the cursor is
deleted. By default, this is not bound to a key.
quoted-insert (C-q or C-v)
-
Add the next character typed to the line verbatim. This is
how to insert key sequences like C-q, for example.
self-insert (a, b, A, 1, !, ...)
-
Insert yourself.
transpose-chars (C-t)
-
Drag the character before the cursor forward over
the character at the cursor, moving the
cursor forward as well. If the insertion point
is at the end of the line, then this
transposes the last two characters of the line.
Negative arguments have no effect.
transpose-words (M-t)
-
Drag the word before point past the word after point,
moving point past that word as well.
If the insertion point is at the end of the line, this transposes
the last two words on the line.
upcase-word (M-u)
-
Uppercase the current (or following) word. With a negative argument,
uppercase the previous word, but do not move the cursor.
downcase-word (M-l)
-
Lowercase the current (or following) word. With a negative argument,
lowercase the previous word, but do not move the cursor.
capitalize-word (M-c)
-
Capitalize the current (or following) word. With a negative argument,
capitalize the previous word, but do not move the cursor.
overwrite-mode ()
-
Toggle overwrite mode. With an explicit positive numeric argument,
switches to overwrite mode. With an explicit non-positive numeric
argument, switches to insert mode. This command affects only
emacs
mode; vi
mode does overwrite differently.
Each call to readline()
starts in insert mode.
In overwrite mode, characters bound to self-insert
replace
the text at point rather than pushing the text to the right.
Characters bound to backward-delete-char
replace the character
before point with a space.
By default, this command is unbound.
8.4.4 Killing And Yanking
kill-line (C-k)
-
Kill the text from point to the end of the line.
backward-kill-line (C-x Rubout)
-
Kill backward to the beginning of the line.
unix-line-discard (C-u)
-
Kill backward from the cursor to the beginning of the current line.
kill-whole-line ()
-
Kill all characters on the current line, no matter where point is.
By default, this is unbound.
kill-word (M-d)
-
Kill from point to the end of the current word, or if between
words, to the end of the next word.
Word boundaries are the same as
forward-word
.
backward-kill-word (M-DEL)
-
Kill the word behind point.
Word boundaries are the same as
backward-word
.
shell-kill-word ()
-
Kill from point to the end of the current word, or if between
words, to the end of the next word.
Word boundaries are the same as
shell-forward-word
.
shell-backward-kill-word ()
-
Kill the word behind point.
Word boundaries are the same as
shell-backward-word
.
unix-word-rubout (C-w)
-
Kill the word behind point, using white space as a word boundary.
The killed text is saved on the kill-ring.
unix-filename-rubout ()
-
Kill the word behind point, using white space and the slash character
as the word boundaries.
The killed text is saved on the kill-ring.
delete-horizontal-space ()
-
Delete all spaces and tabs around point. By default, this is unbound.
kill-region ()
-
Kill the text in the current region.
By default, this command is unbound.
copy-region-as-kill ()
-
Copy the text in the region to the kill buffer, so it can be yanked
right away. By default, this command is unbound.
copy-backward-word ()
-
Copy the word before point to the kill buffer.
The word boundaries are the same as
backward-word
.
By default, this command is unbound.
copy-forward-word ()
-
Copy the word following point to the kill buffer.
The word boundaries are the same as
forward-word
.
By default, this command is unbound.
yank (C-y)
-
Yank the top of the kill ring into the buffer at point.
yank-pop (M-y)
-
Rotate the kill-ring, and yank the new top. You can only do this if
the prior command is
yank
or yank-pop
.
8.4.5 Specifying Numeric Arguments
digit-argument (M-0, M-1, ... M--)
-
Add this digit to the argument already accumulating, or start a new
argument. M-- starts a negative argument.
universal-argument ()
-
This is another way to specify an argument.
If this command is followed by one or more digits, optionally with a
leading minus sign, those digits define the argument.
If the command is followed by digits, executing
universal-argument
again ends the numeric argument, but is otherwise ignored.
As a special case, if this command is immediately followed by a
character that is neither a digit or minus sign, the argument count
for the next command is multiplied by four.
The argument count is initially one, so executing this function the
first time makes the argument count four, a second time makes the
argument count sixteen, and so on.
By default, this is not bound to a key.
8.4.6 Letting Readline Type For You
complete (TAB)
-
Attempt to perform completion on the text before point.
The actual completion performed is application-specific.
Bash attempts completion treating the text as a variable (if the
text begins with `$'), username (if the text begins with
`~'), hostname (if the text begins with `@'), or
command (including aliases and functions) in turn. If none
of these produces a match, filename completion is attempted.
possible-completions (M-?)
-
List the possible completions of the text before point.
When displaying completions, Readline sets the number of columns used
for display to the value of
completion-display-width
, the value of
the environment variable COLUMNS
, or the screen width, in that order.
insert-completions (M-*)
-
Insert all completions of the text before point that would have
been generated by
possible-completions
.
menu-complete ()
-
Similar to
complete
, but replaces the word to be completed
with a single match from the list of possible completions.
Repeated execution of menu-complete
steps through the list
of possible completions, inserting each match in turn.
At the end of the list of completions, the bell is rung
(subject to the setting of bell-style
)
and the original text is restored.
An argument of n moves n positions forward in the list
of matches; a negative argument may be used to move backward
through the list.
This command is intended to be bound to TAB, but is unbound
by default.
menu-complete-backward ()
-
Identical to
menu-complete
, but moves backward through the list
of possible completions, as if menu-complete
had been given a
negative argument.
delete-char-or-list ()
-
Deletes the character under the cursor if not at the beginning or
end of the line (like
delete-char
).
If at the end of the line, behaves identically to
possible-completions
.
This command is unbound by default.
complete-filename (M-/)
-
Attempt filename completion on the text before point.
possible-filename-completions (C-x /)
-
List the possible completions of the text before point,
treating it as a filename.
complete-username (M-~)
-
Attempt completion on the text before point, treating
it as a username.
possible-username-completions (C-x ~)
-
List the possible completions of the text before point,
treating it as a username.
complete-variable (M-$)
-
Attempt completion on the text before point, treating
it as a shell variable.
possible-variable-completions (C-x $)
-
List the possible completions of the text before point,
treating it as a shell variable.
complete-hostname (M-@)
-
Attempt completion on the text before point, treating
it as a hostname.
possible-hostname-completions (C-x @)
-
List the possible completions of the text before point,
treating it as a hostname.
complete-command (M-!)
-
Attempt completion on the text before point, treating
it as a command name. Command completion attempts to
match the text against aliases, reserved words, shell
functions, shell builtins, and finally executable filenames,
in that order.
possible-command-completions (C-x !)
-
List the possible completions of the text before point,
treating it as a command name.
dynamic-complete-history (M-TAB)
-
Attempt completion on the text before point, comparing
the text against lines from the history list for possible
completion matches.
dabbrev-expand ()
-
Attempt menu completion on the text before point, comparing
the text against lines from the history list for possible
completion matches.
complete-into-braces (M-{)
-
Perform filename completion and insert the list of possible completions
enclosed within braces so the list is available to the shell
(see section 3.5.1 Brace Expansion).
8.4.7 Keyboard Macros
start-kbd-macro (C-x ()
-
Begin saving the characters typed into the current keyboard macro.
end-kbd-macro (C-x ))
-
Stop saving the characters typed into the current keyboard macro
and save the definition.
call-last-kbd-macro (C-x e)
-
Re-execute the last keyboard macro defined, by making the characters
in the macro appear as if typed at the keyboard.
print-last-kbd-macro ()
-
Print the last keboard macro defined in a format suitable for the
inputrc file.
8.4.8 Some Miscellaneous Commands
re-read-init-file (C-x C-r)
-
Read in the contents of the inputrc file, and incorporate
any bindings or variable assignments found there.
abort (C-g)
-
Abort the current editing command and
ring the terminal's bell (subject to the setting of
bell-style
).
do-uppercase-version (M-a, M-b, M-x, ...)
-
If the metafied character x is lowercase, run the command
that is bound to the corresponding uppercase character.
prefix-meta (ESC)
-
Metafy the next character typed. This is for keyboards
without a meta key. Typing `ESC f' is equivalent to typing
M-f.
undo (C-_ or C-x C-u)
-
Incremental undo, separately remembered for each line.
revert-line (M-r)
-
Undo all changes made to this line. This is like executing the
undo
command enough times to get back to the beginning.
tilde-expand (M-&)
-
Perform tilde expansion on the current word.
set-mark (C-@)
-
Set the mark to the point. If a
numeric argument is supplied, the mark is set to that position.
exchange-point-and-mark (C-x C-x)
-
Swap the point with the mark. The current cursor position is set to
the saved position, and the old cursor position is saved as the mark.
character-search (C-])
-
A character is read and point is moved to the next occurrence of that
character. A negative count searches for previous occurrences.
character-search-backward (M-C-])
-
A character is read and point is moved to the previous occurrence
of that character. A negative count searches for subsequent
occurrences.
skip-csi-sequence ()
-
Read enough characters to consume a multi-key sequence such as those
defined for keys like Home and End. Such sequences begin with a
Control Sequence Indicator (CSI), usually ESC-[. If this sequence is
bound to "\e[", keys producing such sequences will have no effect
unless explicitly bound to a readline command, instead of inserting
stray characters into the editing buffer. This is unbound by default,
but usually bound to ESC-[.
insert-comment (M-#)
-
Without a numeric argument, the value of the
comment-begin
variable is inserted at the beginning of the current line.
If a numeric argument is supplied, this command acts as a toggle: if
the characters at the beginning of the line do not match the value
of comment-begin
, the value is inserted, otherwise
the characters in comment-begin
are deleted from the beginning of
the line.
In either case, the line is accepted as if a newline had been typed.
The default value of comment-begin
causes this command
to make the current line a shell comment.
If a numeric argument causes the comment character to be removed, the line
will be executed by the shell.
dump-functions ()
-
Print all of the functions and their key bindings to the
Readline output stream. If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an inputrc file. This command is unbound by default.
dump-variables ()
-
Print all of the settable variables and their values to the
Readline output stream. If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an inputrc file. This command is unbound by default.
dump-macros ()
-
Print all of the Readline key sequences bound to macros and the
strings they output. If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an inputrc file. This command is unbound by default.
glob-complete-word (M-g)
-
The word before point is treated as a pattern for pathname expansion,
with an asterisk implicitly appended. This pattern is used to
generate a list of matching file names for possible completions.
glob-expand-word (C-x *)
-
The word before point is treated as a pattern for pathname expansion,
and the list of matching file names is inserted, replacing the word.
If a numeric argument is supplied, a `*' is appended before
pathname expansion.
glob-list-expansions (C-x g)
-
The list of expansions that would have been generated by
glob-expand-word
is displayed, and the line is redrawn.
If a numeric argument is supplied, a `*' is appended before
pathname expansion.
display-shell-version (C-x C-v)
-
Display version information about the current instance of Bash.
shell-expand-line (M-C-e)
-
Expand the line as the shell does.
This performs alias and history expansion as well as all of the shell
word expansions (see section 3.5 Shell Expansions).
history-expand-line (M-^)
-
Perform history expansion on the current line.
magic-space ()
-
Perform history expansion on the current line and insert a space
(see section 9.3 History Expansion).
alias-expand-line ()
-
Perform alias expansion on the current line (see section 6.6 Aliases).
history-and-alias-expand-line ()
-
Perform history and alias expansion on the current line.
insert-last-argument (M-. or M-_)
-
A synonym for
yank-last-arg
.
operate-and-get-next (C-o)
-
Accept the current line for execution and fetch the next line
relative to the current line from the history for editing. Any
argument is ignored.
edit-and-execute-command (C-xC-e)
-
Invoke an editor on the current command line, and execute the result as shell
commands.
Bash attempts to invoke
$VISUAL
, $EDITOR
, and emacs
as the editor, in that order.
8.5 Readline vi Mode
While the Readline library does not have a full set of vi
editing functions, it does contain enough to allow simple editing
of the line. The Readline vi
mode behaves as specified in
the POSIX standard.
In order to switch interactively between emacs
and vi
editing modes, use the `set -o emacs' and `set -o vi'
commands (see section 4.3.1 The Set Builtin).
The Readline default is emacs
mode.
When you enter a line in vi
mode, you are already placed in
`insertion' mode, as if you had typed an `i'. Pressing ESC
switches you into `command' mode, where you can edit the text of the
line with the standard vi
movement keys, move to previous
history lines with `k' and subsequent lines with `j', and
so forth.
8.6 Programmable Completion
When word completion is attempted for an argument to a command for
which a completion specification (a compspec) has been defined
using the complete
builtin (see section 8.7 Programmable Completion Builtins),
the programmable completion facilities are invoked.
First, the command name is identified.
If a compspec has been defined for that command, the
compspec is used to generate the list of possible completions for the word.
If the command word is the empty string (completion attempted at the
beginning of an empty line), any compspec defined with
the `-E' option to complete
is used.
If the command word is a full pathname, a compspec for the full
pathname is searched for first.
If no compspec is found for the full pathname, an attempt is made to
find a compspec for the portion following the final slash.
If those searches do not result in a compspec, any compspec defined with
the `-D' option to complete
is used as the default.
Once a compspec has been found, it is used to generate the list of
matching words.
If a compspec is not found, the default Bash completion
described above (see section 8.4.6 Letting Readline Type For You) is performed.
First, the actions specified by the compspec are used.
Only matches which are prefixed by the word being completed are
returned.
When the `-f' or `-d' option is used for filename or
directory name completion, the shell variable FIGNORE
is
used to filter the matches.
See section 5.2 Bash Variables, for a description of FIGNORE
.
Any completions specified by a filename expansion pattern to the
`-G' option are generated next.
The words generated by the pattern need not match the word being completed.
The GLOBIGNORE
shell variable is not used to filter the matches,
but the FIGNORE
shell variable is used.
Next, the string specified as the argument to the `-W' option
is considered.
The string is first split using the characters in the IFS
special variable as delimiters.
Shell quoting is honored.
Each word is then expanded using
brace expansion, tilde expansion, parameter and variable expansion,
command substitution, and arithmetic expansion,
as described above (see section 3.5 Shell Expansions).
The results are split using the rules described above
(see section 3.5.7 Word Splitting).
The results of the expansion are prefix-matched against the word being
completed, and the matching words become the possible completions.
After these matches have been generated, any shell function or command
specified with the `-F' and `-C' options is invoked.
When the command or function is invoked, the COMP_LINE
,
COMP_POINT
, COMP_KEY
, and COMP_TYPE
variables are
assigned values as described above (see section 5.2 Bash Variables).
If a shell function is being invoked, the COMP_WORDS
and
COMP_CWORD
variables are also set.
When the function or command is invoked, the first argument ($1) is the
name of the command whose arguments are being completed, the
second argument ($2) is the word being completed, and the third argument
($3) is the word preceding the word being completed on the current command
line.
No filtering of the generated completions against the word being completed
is performed; the function or command has complete freedom in generating
the matches.
Any function specified with `-F' is invoked first.
The function may use any of the shell facilities, including the
compgen
and compopt
builtins described below
(see section 8.7 Programmable Completion Builtins), to generate the matches.
It must put the possible completions in the COMPREPLY
array
variable, one per array element.
Next, any command specified with the `-C' option is invoked
in an environment equivalent to command substitution.
It should print a list of completions, one per line, to
the standard output.
Backslash may be used to escape a newline, if necessary.
After all of the possible completions are generated, any filter
specified with the `-X' option is applied to the list.
The filter is a pattern as used for pathname expansion; a `&'
in the pattern is replaced with the text of the word being completed.
A literal `&' may be escaped with a backslash; the backslash
is removed before attempting a match.
Any completion that matches the pattern will be removed from the list.
A leading `!' negates the pattern; in this case any completion
not matching the pattern will be removed.
Finally, any prefix and suffix specified with the `-P' and `-S'
options are added to each member of the completion list, and the result is
returned to the Readline completion code as the list of possible
completions.
If the previously-applied actions do not generate any matches, and the
`-o dirnames' option was supplied to complete
when the
compspec was defined, directory name completion is attempted.
If the `-o plusdirs' option was supplied to complete
when
the compspec was defined, directory name completion is attempted and any
matches are added to the results of the other actions.
By default, if a compspec is found, whatever it generates is returned to
the completion code as the full set of possible completions.
The default Bash completions are not attempted, and the Readline default
of filename completion is disabled.
If the `-o bashdefault' option was supplied to complete
when
the compspec was defined, the default Bash completions are attempted
if the compspec generates no matches.
If the `-o default' option was supplied to complete
when the
compspec was defined, Readline's default completion will be performed
if the compspec (and, if attempted, the default Bash completions)
generate no matches.
When a compspec indicates that directory name completion is desired,
the programmable completion functions force Readline to append a slash
to completed names which are symbolic links to directories, subject to
the value of the mark-directories Readline variable, regardless
of the setting of the mark-symlinked-directories Readline variable.
There is some support for dynamically modifying completions. This is
most useful when used in combination with a default completion specified
with `-D'. It's possible for shell functions executed as completion
handlers to indicate that completion should be retried by returning an
exit status of 124. If a shell function returns 124, and changes
the compspec associated with the command on which completion is being
attempted (supplied as the first argument when the function is executed),
programmable completion restarts from the beginning, with an
attempt to find a new compspec for that command. This allows a set of
completions to be built dynamically as completion is attempted, rather than
being loaded all at once.
For instance, assuming that there is a library of compspecs, each kept in a
file corresponding to the name of the command, the following default
completion function would load completions dynamically:
| _completion_loader()
{
. "/etc/bash_completion.d/$1.sh" >/dev/null 2>&1 && return 124
}
complete -D -F _completion_loader -o bashdefault -o default
|
8.7 Programmable Completion Builtins
Three builtin commands are available to manipulate the programmable completion
facilities: one to specify how the arguments to a particular command are to
be completed, and two to modify the completion as it is happening.
compgen
-
Generate possible completion matches for word according to
the options, which may be any option accepted by the
complete
builtin with the exception of `-p' and `-r', and write
the matches to the standard output.
When using the `-F' or `-C' options, the various shell variables
set by the programmable completion facilities, while available, will not
have useful values.
The matches will be generated in the same way as if the programmable
completion code had generated them directly from a completion specification
with the same flags.
If word is specified, only those completions matching word
will be displayed.
The return value is true unless an invalid option is supplied, or no
matches were generated.
complete
-
| complete [-abcdefgjksuv] [-o comp-option] [-DE] [-A action] [-G globpat] [-W wordlist]
[-F function] [-C command] [-X filterpat]
[-P prefix] [-S suffix] name [name ...]
complete -pr [-DE] [name ...]
|
Specify how arguments to each name should be completed.
If the `-p' option is supplied, or if no options are supplied, existing
completion specifications are printed in a way that allows them to be
reused as input.
The `-r' option removes a completion specification for
each name, or, if no names are supplied, all
completion specifications.
The `-D' option indicates that the remaining options and actions should
apply to the "default" command completion; that is, completion attempted
on a command for which no completion has previously been defined.
The `-E' option indicates that the remaining options and actions should
apply to "empty" command completion; that is, completion attempted on a
blank line.
The process of applying these completion specifications when word completion
is attempted is described above (see section 8.6 Programmable Completion). The
`-D' option takes precedence over `-E'.
Other options, if specified, have the following meanings.
The arguments to the `-G', `-W', and `-X' options
(and, if necessary, the `-P' and `-S' options)
should be quoted to protect them from expansion before the
complete
builtin is invoked.
-o comp-option
- The comp-option controls several aspects of the compspec's behavior
beyond the simple generation of completions.
comp-option may be one of:
bashdefault
- Perform the rest of the default Bash completions if the compspec
generates no matches.
default
- Use Readline's default filename completion if the compspec generates
no matches.
dirnames
- Perform directory name completion if the compspec generates no matches.
filenames
- Tell Readline that the compspec generates filenames, so it can perform any
filename-specific processing (like adding a slash to directory names
quoting special characters, or suppressing trailing spaces).
This option is intended to be used with shell functions specified
with `-F'.
noquote
- Tell Readline not to quote the completed words if they are filenames
(quoting filenames is the default).
nospace
- Tell Readline not to append a space (the default) to words completed at
the end of the line.
plusdirs
- After any matches defined by the compspec are generated,
directory name completion is attempted and any
matches are added to the results of the other actions.
-A action
- The action may be one of the following to generate a list of possible
completions:
alias
- Alias names. May also be specified as `-a'.
arrayvar
- Array variable names.
binding
- Readline key binding names (see section 8.4 Bindable Readline Commands).
builtin
- Names of shell builtin commands. May also be specified as `-b'.
command
- Command names. May also be specified as `-c'.
directory
- Directory names. May also be specified as `-d'.
disabled
- Names of disabled shell builtins.
enabled
- Names of enabled shell builtins.
export
- Names of exported shell variables. May also be specified as `-e'.
file
- File names. May also be specified as `-f'.
function
- Names of shell functions.
group
- Group names. May also be specified as `-g'.
helptopic
- Help topics as accepted by the
help
builtin (see section 4.2 Bash Builtin Commands).
hostname
- Hostnames, as taken from the file specified by the
HOSTFILE
shell variable (see section 5.2 Bash Variables).
job
- Job names, if job control is active. May also be specified as `-j'.
keyword
- Shell reserved words. May also be specified as `-k'.
running
- Names of running jobs, if job control is active.
service
- Service names. May also be specified as `-s'.
setopt
- Valid arguments for the `-o' option to the
set
builtin
(see section 4.3.1 The Set Builtin).
shopt
- Shell option names as accepted by the
shopt
builtin
(see section 4.2 Bash Builtin Commands).
signal
- Signal names.
stopped
- Names of stopped jobs, if job control is active.
user
- User names. May also be specified as `-u'.
variable
- Names of all shell variables. May also be specified as `-v'.
-C command
- command is executed in a subshell environment, and its output is
used as the possible completions.
-F function
- The shell function function is executed in the current shell
environment.
When it is executed, $1 is the name of the command whose arguments are
being completed, $2 is the word being completed, and $3 is the word
preceding the word being completed, as described above
(see section 8.6 Programmable Completion).
When it finishes, the possible completions are retrieved from the value
of the
COMPREPLY
array variable.
-G globpat
- The filename expansion pattern globpat is expanded to generate
the possible completions.
-P prefix
- prefix is added at the beginning of each possible completion
after all other options have been applied.
-S suffix
- suffix is appended to each possible completion
after all other options have been applied.
-W wordlist
- The wordlist is split using the characters in the
IFS
special variable as delimiters, and each resultant word
is expanded.
The possible completions are the members of the resultant list which
match the word being completed.
-X filterpat
- filterpat is a pattern as used for filename expansion.
It is applied to the list of possible completions generated by the
preceding options and arguments, and each completion matching
filterpat is removed from the list.
A leading `!' in filterpat negates the pattern; in this
case, any completion not matching filterpat is removed.
The return value is true unless an invalid option is supplied, an option
other than `-p' or `-r' is supplied without a name
argument, an attempt is made to remove a completion specification for
a name for which no specification exists, or
an error occurs adding a completion specification.
compopt
-
| compopt [-o option] [-DE] [+o option] [name]
|
Modify completion options for each name according to the
options, or for the currently-executing completion if no names
are supplied.
If no options are given, display the completion options for each
name or the current completion.
The possible values of option are those valid for the complete
builtin described above.
The `-D' option indicates that the remaining options should
apply to the "default" command completion; that is, completion attempted
on a command for which no completion has previously been defined.
The `-E' option indicates that the remaining options should
apply to "empty" command completion; that is, completion attempted on a
blank line.
The `-D' option takes precedence over `-E'.
The return value is true unless an invalid option is supplied, an attempt
is made to modify the options for a name for which no completion
specification exists, or an output error occurs.
8.8 A Programmable Completion Example
The most common way to obtain additional completion functionality beyond
the default actions complete
and compgen
provide is to use
a shell function and bind it to a particular command using complete -F
.
The following function provides completions for the cd
builtin.
It is a reasonably good example of what shell functions must do when
used for completion. This function uses the word passsed as $2
to determine the directory name to complete. You can also use the
COMP_WORDS
array variable; the current word is indexed by the
COMP_CWORD
variable.
The function relies on the complete
and compgen
builtins
to do much of the work, adding only the things that the Bash cd
does beyond accepting basic directory names:
tilde expansion (see section 3.5.2 Tilde Expansion),
searching directories in $CDPATH, which is described above
(see section 4.1 Bourne Shell Builtins),
and basic support for the cdable_vars
shell option
(see section 4.3.2 The Shopt Builtin).
_comp_cd
modifies the value of IFS so that it contains only
a newline to accommodate file names containing spaces and tabs --
compgen
prints the possible completions it generates one per line.
Possible completions go into the COMPREPLY array variable, one
completion per array element. The programmable completion system retrieves
the completions from there when the function returns.
| # A completion function for the cd builtin
# based on the cd completion function from the bash_completion package
_comp_cd()
{
local IFS=$' \t\n' # normalize IFS
local cur _skipdot _cdpath
local i j k
# Tilde expansion, with side effect of expanding tilde to full pathname
case "$2" in
\~*) eval cur="$2" ;;
*) cur=$2 ;;
esac
# no cdpath or absolute pathname -- straight directory completion
if [[ -z "${CDPATH:-}" ]] || [[ "$cur" == @(./*|../*|/*) ]]; then
# compgen prints paths one per line; could also use while loop
IFS=$'\n'
COMPREPLY=( $(compgen -d -- "$cur") )
IFS=$' \t\n'
# CDPATH+directories in the current directory if not in CDPATH
else
IFS=$'\n'
_skipdot=false
# preprocess CDPATH to convert null directory names to .
_cdpath=${CDPATH/#:/.:}
_cdpath=${_cdpath//::/:.:}
_cdpath=${_cdpath/%:/:.}
for i in ${_cdpath//:/$'\n'}; do
if [[ $i -ef . ]]; then _skipdot=true; fi
k="${#COMPREPLY[@]}"
for j in $( compgen -d -- "$i/$cur" ); do
COMPREPLY[k++]=${j#$i/} # cut off directory
done
done
$_skipdot || COMPREPLY+=( $(compgen -d -- "$cur") )
IFS=$' \t\n'
fi
# variable names if appropriate shell option set and no completions
if shopt -q cdable_vars && [[ ${#COMPREPLY[@]} -eq 0 ]]; then
COMPREPLY=( $(compgen -v -- "$cur") )
fi
return 0
}
|
We install the completion function using the `-F' option to
complete
:
| # Tell readline to quote appropriate and append slashes to directories;
# use the bash default completion for other arguments
complete -o filenames -o nospace -o bashdefault -F _comp_cd cd
|
Since we'd like Bash and Readline to take care of some
of the other details for us, we use several other options to tell Bash
and Readline what to do. The `-o filenames' option tells Readline
that the possible completions should be treated as filenames, and quoted
appropriately. That option will also cause Readline to append a slash to
filenames it can determine are directories (which is why we might want to
extend _comp_cd
to append a slash if we're using directories found
via CDPATH: Readline can't tell those completions are directories).
The `-o nospace' option tells Readline to not append a space
character to the directory name, in case we want to append to it.
The `-o bashdefault' option brings in the rest of the "Bash default"
completions -- possible completion that Bash adds to the default Readline
set. These include things like command name completion, variable completion
for words beginning with `{', completions containing pathname
expansion patterns (see section 3.5.8 Filename Expansion), and so on.
Once installed using complete
, _comp_cd
will be called every
time we attempt word completion for a cd
command.
Many more examples -- an extensive collection of completions for most of
the common GNU, Unix, and Linux commands -- are available as part of the
bash_completion project. This is installed by default on many GNU/Linux
distributions. Originally written by Ian Macdonald, the project now lives
at http://bash-completion.alioth.debian.org/. There are ports for
other systems such as Solaris and Mac OS X.
An older version of the bash_completion package is distributed with bash
in the `examples/complete' subdirectory.
9. Using History Interactively
This chapter describes how to use the GNU History Library
interactively, from a user's standpoint.
It should be considered a user's guide.
For information on using the GNU History Library in other programs,
see the GNU Readline Library Manual.
9.1 Bash History Facilities
When the `-o history' option to the set
builtin
is enabled (see section 4.3.1 The Set Builtin),
the shell provides access to the command history,
the list of commands previously typed.
The value of the HISTSIZE
shell variable is used as the
number of commands to save in a history list.
The text of the last $HISTSIZE
commands (default 500) is saved.
The shell stores each command in the history list prior to
parameter and variable expansion
but after history expansion is performed, subject to the
values of the shell variables
HISTIGNORE
and HISTCONTROL
.
When the shell starts up, the history is initialized from the
file named by the HISTFILE
variable (default `~/.bash_history').
The file named by the value of HISTFILE
is truncated, if
necessary, to contain no more than the number of lines specified by
the value of the HISTFILESIZE
variable.
When a shell with history enabled exits, the last
$HISTSIZE
lines are copied from the history list to the file
named by $HISTFILE
.
If the histappend
shell option is set (see section 4.2 Bash Builtin Commands),
the lines are appended to the history file,
otherwise the history file is overwritten.
If HISTFILE
is unset, or if the history file is unwritable, the history is not saved.
After saving the history, the history file is truncated
to contain no more than $HISTFILESIZE
lines.
If HISTFILESIZE
is unset, or set to null, a non-numeric value, or
a numeric value less than zero, the history file is not truncated.
If the HISTTIMEFORMAT
is set, the time stamp information
associated with each history entry is written to the history file,
marked with the history comment character.
When the history file is read, lines beginning with the history
comment character followed immediately by a digit are interpreted
as timestamps for the previous history line.
The builtin command fc
may be used to list or edit and re-execute
a portion of the history list.
The history
builtin may be used to display or modify the history
list and manipulate the history file.
When using command-line editing, search commands
are available in each editing mode that provide access to the
history list (see section 8.4.2 Commands For Manipulating The History).
The shell allows control over which commands are saved on the history
list. The HISTCONTROL
and HISTIGNORE
variables may be set to cause the shell to save only a subset of the
commands entered.
The cmdhist
shell option, if enabled, causes the shell to attempt to save each
line of a multi-line command in the same history entry, adding
semicolons where necessary to preserve syntactic correctness.
The lithist
shell option causes the shell to save the command with embedded newlines
instead of semicolons.
The shopt
builtin is used to set these options.
See section 4.2 Bash Builtin Commands, for a description of shopt
.
9.2 Bash History Builtins
Bash provides two builtin commands which manipulate the
history list and history file.
fc
-
| fc [-e ename] [-lnr] [first] [last]
fc -s [pat=rep] [command]
|
The first form selects a range of commands from first to
last from the history list and displays or edits and re-executes
them.
Both first and
last may be specified as a string (to locate the most recent
command beginning with that string) or as a number (an index into the
history list, where a negative number is used as an offset from the
current command number). If last is not specified it is set to
first. If first is not specified it is set to the previous
command for editing and -16 for listing. If the `-l' flag is
given, the commands are listed on standard output. The `-n' flag
suppresses the command numbers when listing. The `-r' flag
reverses the order of the listing. Otherwise, the editor given by
ename is invoked on a file containing those commands. If
ename is not given, the value of the following variable expansion
is used: ${FCEDIT:-${EDITOR:-vi}}
. This says to use the
value of the FCEDIT
variable if set, or the value of the
EDITOR
variable if that is set, or vi
if neither is set.
When editing is complete, the edited commands are echoed and executed.
In the second form, command is re-executed after each instance
of pat in the selected command is replaced by rep.
command is intepreted the same as first above.
A useful alias to use with the fc
command is r='fc -s'
, so
that typing `r cc' runs the last command beginning with cc
and typing `r' re-executes the last command (see section 6.6 Aliases).
history
-
| history [n]
history -c
history -d offset
history [-anrw] [filename]
history -ps arg
|
With no options, display the history list with line numbers.
Lines prefixed with a `*' have been modified.
An argument of n lists only the last n lines.
If the shell variable HISTTIMEFORMAT
is set and not null,
it is used as a format string for strftime to display
the time stamp associated with each displayed history entry.
No intervening blank is printed between the formatted time stamp
and the history line.
Options, if supplied, have the following meanings:
-c
- Clear the history list. This may be combined
with the other options to replace the history list completely.
-d offset
- Delete the history entry at position offset.
offset should be specified as it appears when the history is
displayed.
-a
- Append the new
history lines (history lines entered since the beginning of the
current Bash session) to the history file.
-n
- Append the history lines not already read from the history file
to the current history list. These are lines appended to the history
file since the beginning of the current Bash session.
-r
- Read the history file and append its contents to
the history list.
-w
- Write out the current history list to the history file.
-p
- Perform history substitution on the args and display the result
on the standard output, without storing the results in the history list.
-s
- The args are added to the end of
the history list as a single entry.
When any of the `-w', `-r', `-a', or `-n' options is
used, if filename
is given, then it is used as the history file. If not, then
the value of the HISTFILE
variable is used.
9.3 History Expansion
The History library provides a history expansion feature that is similar
to the history expansion provided by csh
. This section
describes the syntax used to manipulate the history information.
History expansions introduce words from the history list into
the input stream, making it easy to repeat commands, insert the
arguments to a previous command into the current input line, or
fix errors in previous commands quickly.
History expansion takes place in two parts. The first is to determine
which line from the history list should be used during substitution.
The second is to select portions of that line for inclusion into the
current one. The line selected from the history is called the
event, and the portions of that line that are acted upon are
called words. Various modifiers are available to manipulate
the selected words. The line is broken into words in the same fashion
that Bash does, so that several words
surrounded by quotes are considered one word.
History expansions are introduced by the appearance of the
history expansion character, which is `!' by default.
Only `\' and `'' may be used to escape the history expansion
character.
Several shell options settable with the shopt
builtin (see section 4.2 Bash Builtin Commands) may be used to tailor
the behavior of history expansion. If the
histverify
shell option is enabled, and Readline
is being used, history substitutions are not immediately passed to
the shell parser.
Instead, the expanded line is reloaded into the Readline
editing buffer for further modification.
If Readline is being used, and the histreedit
shell option is enabled, a failed history expansion will be
reloaded into the Readline editing buffer for correction.
The `-p' option to the history
builtin command
may be used to see what a history expansion will do before using it.
The `-s' option to the history
builtin may be used to
add commands to the end of the history list without actually executing
them, so that they are available for subsequent recall.
This is most useful in conjunction with Readline.
The shell allows control of the various characters used by the
history expansion mechanism with the histchars
variable,
as explained above (see section 5.2 Bash Variables). The shell uses
the history comment character to mark history timestamps when
writing the history file.
9.3.1 Event Designators
An event designator is a reference to a command line entry in the
history list.
Unless the reference is absolute, events are relative to the current
position in the history list.
!
- Start a history substitution, except when followed by a space, tab,
the end of the line, `=' or `(' (when the
extglob
shell option is enabled using the shopt
builtin).
!n
- Refer to command line n.
!-n
- Refer to the command n lines back.
!!
- Refer to the previous command. This is a synonym for `!-1'.
!string
- Refer to the most recent command
preceding the current position in the history list
starting with string.
!?string[?]
- Refer to the most recent command
preceding the current position in the history list
containing string.
The trailing
`?' may be omitted if the string is followed immediately by
a newline.
^string1^string2^
- Quick Substitution. Repeat the last command, replacing string1
with string2. Equivalent to
!!:s/string1/string2/
.
!#
- The entire command line typed so far.
9.3.2 Word Designators
Word designators are used to select desired words from the event.
A `:' separates the event specification from the word designator. It
may be omitted if the word designator begins with a `^', `$',
`*', `-', or `%'. Words are numbered from the beginning
of the line, with the first word being denoted by 0 (zero). Words are
inserted into the current line separated by single spaces.
For example,
!!
- designates the preceding command. When you type this, the preceding
command is repeated in toto.
!!:$
- designates the last argument of the preceding command. This may be
shortened to
!$
.
!fi:2
- designates the second argument of the most recent command starting with
the letters
fi
.
Here are the word designators:
0 (zero)
- The
0
th word. For many applications, this is the command word.
n
- The nth word.
^
- The first argument; that is, word 1.
$
- The last argument.
%
- The word matched by the most recent `?string?' search.
x-y
- A range of words; `-y' abbreviates `0-y'.
*
- All of the words, except the
0
th. This is a synonym for `1-$'.
It is not an error to use `*' if there is just one word in the event;
the empty string is returned in that case.
x*
- Abbreviates `x-$'
x-
- Abbreviates `x-$' like `x*', but omits the last word.
If a word designator is supplied without an event specification, the
previous command is used as the event.
9.3.3 Modifiers
After the optional word designator, you can add a sequence of one or more
of the following modifiers, each preceded by a `:'.
h
- Remove a trailing pathname component, leaving only the head.
t
- Remove all leading pathname components, leaving the tail.
r
- Remove a trailing suffix of the form `.suffix', leaving
the basename.
e
- Remove all but the trailing suffix.
p
- Print the new command but do not execute it.
q
- Quote the substituted words, escaping further substitutions.
x
- Quote the substituted words as with `q',
but break into words at spaces, tabs, and newlines.
s/old/new/
- Substitute new for the first occurrence of old in the
event line. Any delimiter may be used in place of `/'.
The delimiter may be quoted in old and new
with a single backslash. If `&' appears in new,
it is replaced by old. A single backslash will quote
the `&'. The final delimiter is optional if it is the last
character on the input line.
&
- Repeat the previous substitution.
g
a
- Cause changes to be applied over the entire event line. Used in
conjunction with `s', as in
gs/old/new/
,
or with `&'.
G
- Apply the following `s' modifier once to each word in the event.
10. Installing Bash
This chapter provides basic instructions for installing Bash on
the various supported platforms. The distribution supports the
GNU operating systems, nearly every version of Unix, and several
non-Unix systems such as BeOS and Interix.
Other independent ports exist for
MS-DOS, OS/2, and Windows platforms.
10.1 Basic Installation
These are installation instructions for Bash.
The simplest way to compile Bash is:
-
cd
to the directory containing the source code and type
`./configure' to configure Bash for your system. If you're
using csh
on an old version of System V, you might need to
type `sh ./configure' instead to prevent csh
from trying
to execute configure
itself.
Running configure
takes some time.
While running, it prints messages telling which features it is
checking for.
-
Type `make' to compile Bash and build the
bashbug
bug
reporting script.
-
Optionally, type `make tests' to run the Bash test suite.
-
Type `make install' to install
bash
and bashbug
.
This will also install the manual pages and Info file.
The configure
shell script attempts to guess correct
values for various system-dependent variables used during
compilation. It uses those values to create a `Makefile' in
each directory of the package (the top directory, the
`builtins', `doc', and `support' directories,
each directory under `lib', and several others). It also creates a
`config.h' file containing system-dependent definitions.
Finally, it creates a shell script named config.status
that you
can run in the future to recreate the current configuration, a
file `config.cache' that saves the results of its tests to
speed up reconfiguring, and a file `config.log' containing
compiler output (useful mainly for debugging configure
).
If at some point
`config.cache' contains results you don't want to keep, you
may remove or edit it.
To find out more about the options and arguments that the
configure
script understands, type
| bash-2.04$ ./configure --help
|
at the Bash prompt in your Bash source directory.
If you need to do unusual things to compile Bash, please
try to figure out how configure
could check whether or not
to do them, and mail diffs or instructions to
bash-maintainers@gnu.org so they can be
considered for the next release.
The file `configure.ac' is used to create configure
by a program called Autoconf. You only need
`configure.ac' if you want to change it or regenerate
configure
using a newer version of Autoconf. If
you do this, make sure you are using Autoconf version 2.50 or
newer.
You can remove the program binaries and object files from the
source code directory by typing `make clean'. To also remove the
files that configure
created (so you can compile Bash for
a different kind of computer), type `make distclean'.
10.2 Compilers and Options
Some systems require unusual options for compilation or linking
that the configure
script does not know about. You can
give configure
initial values for variables by setting
them in the environment. Using a Bourne-compatible shell, you
can do that on the command line like this:
| CC=c89 CFLAGS=-O2 LIBS=-lposix ./configure
|
On systems that have the env
program, you can do it like this:
| env CPPFLAGS=-I/usr/local/include LDFLAGS=-s ./configure
|
The configuration process uses GCC to build Bash if it
is available.
10.3 Compiling For Multiple Architectures
You can compile Bash for more than one kind of computer at the
same time, by placing the object files for each architecture in their
own directory. To do this, you must use a version of make
that
supports the VPATH
variable, such as GNU make
.
cd
to the
directory where you want the object files and executables to go and run
the configure
script from the source directory. You may need to
supply the `--srcdir=PATH' argument to tell configure
where the
source files are. configure
automatically checks for the
source code in the directory that configure
is in and in `..'.
If you have to use a make
that does not supports the VPATH
variable, you can compile Bash for one architecture at a
time in the source code directory. After you have installed
Bash for one architecture, use `make distclean' before
reconfiguring for another architecture.
Alternatively, if your system supports symbolic links, you can use the
`support/mkclone' script to create a build tree which has
symbolic links back to each file in the source directory. Here's an
example that creates a build directory in the current directory from a
source directory `/usr/gnu/src/bash-2.0':
| bash /usr/gnu/src/bash-2.0/support/mkclone -s /usr/gnu/src/bash-2.0 .
|
The mkclone
script requires Bash, so you must have already built
Bash for at least one architecture before you can create build
directories for other architectures.
10.4 Installation Names
By default, `make install' will install into
`/usr/local/bin', `/usr/local/man', etc. You can
specify an installation prefix other than `/usr/local' by
giving configure
the option `--prefix=PATH',
or by specifying a value for the DESTDIR
`make'
variable when running `make install'.
You can specify separate installation prefixes for
architecture-specific files and architecture-independent files.
If you give configure
the option
`--exec-prefix=PATH', `make install' will use
PATH as the prefix for installing programs and libraries.
Documentation and other data files will still use the regular prefix.
10.5 Specifying the System Type
There may be some features configure
can not figure out
automatically, but need to determine by the type of host Bash
will run on. Usually configure
can figure that
out, but if it prints a message saying it can not guess the host
type, give it the `--host=TYPE' option. `TYPE' can
either be a short name for the system type, such as `sun4',
or a canonical name with three fields: `CPU-COMPANY-SYSTEM'
(e.g., `i386-unknown-freebsd4.2').
See the file `support/config.sub' for the possible
values of each field.
10.6 Sharing Defaults
If you want to set default values for configure
scripts to
share, you can create a site shell script called
config.site
that gives default values for variables like
CC
, cache_file
, and prefix
. configure
looks for `PREFIX/share/config.site' if it exists, then
`PREFIX/etc/config.site' if it exists. Or, you can set the
CONFIG_SITE
environment variable to the location of the site
script. A warning: the Bash configure
looks for a site script,
but not all configure
scripts do.
10.7 Operation Controls
configure
recognizes the following options to control how it
operates.
--cache-file=file
- Use and save the results of the tests in
file instead of `./config.cache'. Set file to
`/dev/null' to disable caching, for debugging
configure
.
--help
- Print a summary of the options to
configure
, and exit.
--quiet
--silent
-q
- Do not print messages saying which checks are being made.
--srcdir=dir
- Look for the Bash source code in directory dir. Usually
configure
can determine that directory automatically.
--version
- Print the version of Autoconf used to generate the
configure
script, and exit.
configure
also accepts some other, not widely used, boilerplate
options. `configure --help' prints the complete list.
10.8 Optional Features
The Bash configure
has a number of `--enable-feature'
options, where feature indicates an optional part of Bash.
There are also several `--with-package' options,
where package is something like `bash-malloc' or `purify'.
To turn off the default use of a package, use
`--without-package'. To configure Bash without a feature
that is enabled by default, use `--disable-feature'.
Here is a complete list of the `--enable-' and
`--with-' options that the Bash configure
recognizes.
--with-afs
- Define if you are using the Andrew File System from Transarc.
--with-bash-malloc
- Use the Bash version of
malloc
in the directory `lib/malloc'. This is not the same
malloc
that appears in GNU libc, but an older version
originally derived from the 4.2 BSD malloc
. This malloc
is very fast, but wastes some space on each allocation.
This option is enabled by default.
The `NOTES' file contains a list of systems for
which this should be turned off, and configure
disables this
option automatically for a number of systems.
--with-curses
- Use the curses library instead of the termcap library. This should
be supplied if your system has an inadequate or incomplete termcap
database.
--with-gnu-malloc
- A synonym for
--with-bash-malloc
.
--with-installed-readline[=PREFIX]
- Define this to make Bash link with a locally-installed version of Readline
rather than the version in `lib/readline'. This works only with
Readline 5.0 and later versions. If PREFIX is
yes
or not
supplied, configure
uses the values of the make variables
includedir
and libdir
, which are subdirectories of prefix
by default, to find the installed version of Readline if it is not in
the standard system include and library directories.
If PREFIX is no
, Bash links with the version in
`lib/readline'.
If PREFIX is set to any other value, configure
treats it as
a directory pathname and looks for
the installed version of Readline in subdirectories of that directory
(include files in PREFIX/include
and the library in
PREFIX/lib
).
--with-purify
- Define this to use the Purify memory allocation checker from Rational
Software.
--enable-minimal-config
- This produces a shell with minimal features, close to the historical
Bourne shell.
There are several `--enable-' options that alter how Bash is
compiled and linked, rather than changing run-time features.
--enable-largefile
- Enable support for large files if the operating system requires special compiler options
to build programs which can access large files. This is enabled by
default, if the operating system provides large file support.
--enable-profiling
- This builds a Bash binary that produces profiling information to be
processed by
gprof
each time it is executed.
--enable-static-link
- This causes Bash to be linked statically, if
gcc
is being used.
This could be used to build a version to use as root's shell.
The `minimal-config' option can be used to disable all of
the following options, but it is processed first, so individual
options may be enabled using `enable-feature'.
All of the following options except for `disabled-builtins',
`directpand-default', and
`xpg-echo-default' are
enabled by default, unless the operating system does not provide the
necessary support.
--enable-alias
- Allow alias expansion and include the
alias
and unalias
builtins (see section 6.6 Aliases).
--enable-arith-for-command
- Include support for the alternate form of the
for
command
that behaves like the C language for
statement
(see section 3.2.4.1 Looping Constructs).
--enable-array-variables
- Include support for one-dimensional array shell variables
(see section 6.7 Arrays).
--enable-bang-history
- Include support for
csh
-like history substitution
(see section 9.3 History Expansion).
--enable-brace-expansion
- Include
csh
-like brace expansion
( b{a,b}c
==> bac bbc
).
See 3.5.1 Brace Expansion, for a complete description.
--enable-casemod-attributes
- Include support for case-modifying attributes in the
declare
builtin
and assignment statements. Variables with the uppercase attribute,
for example, will have their values converted to uppercase upon assignment.
--enable-casemod-expansion
- Include support for case-modifying word expansions.
--enable-command-timing
- Include support for recognizing
time
as a reserved word and for
displaying timing statistics for the pipeline following time
(see section 3.2.2 Pipelines).
This allows pipelines as well as shell builtins and functions to be timed.
--enable-cond-command
- Include support for the
[[
conditional command.
(see section 3.2.4.2 Conditional Constructs).
--enable-cond-regexp
- Include support for matching POSIX regular expressions using the
`=~' binary operator in the
[[
conditional command.
(see section 3.2.4.2 Conditional Constructs).
--enable-coprocesses
- Include support for coprocesses and the
coproc
reserved word
(see section 3.2.2 Pipelines).
--enable-debugger
- Include support for the bash debugger (distributed separately).
--enable-direxpand-default
- Cause the
direxpand
shell option (see section 4.3.2 The Shopt Builtin)
to be enabled by default when the shell starts.
It is normally disabled by default.
--enable-directory-stack
- Include support for a
csh
-like directory stack and the
pushd
, popd
, and dirs
builtins
(see section 6.8 The Directory Stack).
--enable-disabled-builtins
- Allow builtin commands to be invoked via `builtin xxx'
even after
xxx
has been disabled using `enable -n xxx'.
See 4.2 Bash Builtin Commands, for details of the builtin
and
enable
builtin commands.
--enable-dparen-arithmetic
- Include support for the
((...))
command
(see section 3.2.4.2 Conditional Constructs).
--enable-extended-glob
- Include support for the extended pattern matching features described
above under 3.5.8.1 Pattern Matching.
--enable-extended-glob-default
- Set the default value of the extglob shell option described
above under 4.3.2 The Shopt Builtin to be enabled.
--enable-glob-asciirange-default
- Set the default value of the globasciiranges shell option described
above under 4.3.2 The Shopt Builtin to be enabled.
This controls the behavior of character ranges when used in pattern matching
bracket expressions.
--enable-help-builtin
- Include the
help
builtin, which displays help on shell builtins and
variables (see section 4.2 Bash Builtin Commands).
--enable-history
- Include command history and the
fc
and history
builtin commands (see section 9.1 Bash History Facilities).
--enable-job-control
- This enables the job control features (see section 7. Job Control),
if the operating system supports them.
--enable-multibyte
- This enables support for multibyte characters if the operating
system provides the necessary support.
--enable-net-redirections
- This enables the special handling of filenames of the form
/dev/tcp/host/port
and
/dev/udp/host/port
when used in redirections (see section 3.6 Redirections).
--enable-process-substitution
- This enables process substitution (see section 3.5.6 Process Substitution) if
the operating system provides the necessary support.
--enable-progcomp
- Enable the programmable completion facilities
(see section 8.6 Programmable Completion).
If Readline is not enabled, this option has no effect.
--enable-prompt-string-decoding
- Turn on the interpretation of a number of backslash-escaped characters
in the
$PS1
, $PS2
, $PS3
, and $PS4
prompt
strings. See 6.9 Controlling the Prompt, for a complete list of prompt
string escape sequences.
--enable-readline
- Include support for command-line editing and history with the Bash
version of the Readline library (see section 8. Command Line Editing).
--enable-restricted
- Include support for a restricted shell. If this is enabled, Bash,
when called as
rbash
, enters a restricted mode. See
6.10 The Restricted Shell, for a description of restricted mode.
--enable-select
- Include the
select
compound command, which allows the generation of
simple menus (see section 3.2.4.2 Conditional Constructs).
--enable-separate-helpfiles
- Use external files for the documentation displayed by the
help
builtin
instead of storing the text internally.
--enable-single-help-strings
- Store the text displayed by the
help
builtin as a single string for
each help topic. This aids in translating the text to different languages.
You may need to disable this if your compiler cannot handle very long string
literals.
--enable-strict-posix-default
- Make Bash POSIX-conformant by default (see section 6.11 Bash POSIX Mode).
--enable-usg-echo-default
- A synonym for
--enable-xpg-echo-default
.
--enable-xpg-echo-default
- Make the
echo
builtin expand backslash-escaped characters by default,
without requiring the `-e' option.
This sets the default value of the xpg_echo
shell option to on
,
which makes the Bash echo
behave more like the version specified in
the Single Unix Specification, version 3.
See section 4.2 Bash Builtin Commands, for a description of the escape sequences that
echo
recognizes.
The file `config-top.h' contains C Preprocessor
`#define' statements for options which are not settable from
configure
.
Some of these are not meant to be changed; beware of the consequences if
you do.
Read the comments associated with each definition for more
information about its effect.
A. Reporting Bugs
Please report all bugs you find in Bash.
But first, you should
make sure that it really is a bug, and that it appears in the latest
version of Bash.
The latest version of Bash is always available for FTP from
ftp://ftp.gnu.org/pub/gnu/bash/.
Once you have determined that a bug actually exists, use the
bashbug
command to submit a bug report.
If you have a fix, you are encouraged to mail that as well!
Suggestions and `philosophical' bug reports may be mailed
to bug-bash@gnu.org or posted to the Usenet
newsgroup gnu.bash.bug
.
All bug reports should include:
-
The version number of Bash.
-
The hardware and operating system.
-
The compiler used to compile Bash.
-
A description of the bug behaviour.
-
A short script or `recipe' which exercises the bug and may be used
to reproduce it.
bashbug
inserts the first three items automatically into
the template it provides for filing a bug report.
Please send all reports concerning this manual to
bug-bash@gnu.org.
B. Major Differences From The Bourne Shell
Bash implements essentially the same grammar, parameter and
variable expansion, redirection, and quoting as the Bourne Shell.
Bash uses the POSIX standard as the specification of
how these features are to be implemented. There are some
differences between the traditional Bourne shell and Bash; this
section quickly details the differences of significance. A
number of these differences are explained in greater depth in
previous sections.
This section uses the version of sh
included in SVR4.2 (the
last version of the historical Bourne shell) as the baseline reference.
-
Bash is POSIX-conformant, even where the POSIX specification
differs from traditional
sh
behavior (see section 6.11 Bash POSIX Mode).
-
Bash has multi-character invocation options (see section 6.1 Invoking Bash).
-
Bash has command-line editing (see section 8. Command Line Editing) and
the
bind
builtin.
-
Bash provides a programmable word completion mechanism
(see section 8.6 Programmable Completion), and builtin commands
complete
, compgen
, and compopt
, to
manipulate it.
-
Bash has command history (see section 9.1 Bash History Facilities) and the
history
and fc
builtins to manipulate it.
The Bash history list maintains timestamp information and uses the
value of the HISTTIMEFORMAT
variable to display it.
-
Bash implements
csh
-like history expansion
(see section 9.3 History Expansion).
-
Bash has one-dimensional array variables (see section 6.7 Arrays), and the
appropriate variable expansions and assignment syntax to use them.
Several of the Bash builtins take options to act on arrays.
Bash provides a number of built-in array variables.
-
The
$'...'
quoting syntax, which expands ANSI-C
backslash-escaped characters in the text between the single quotes,
is supported (see section 3.1.2.4 ANSI-C Quoting).
-
Bash supports the
$"..."
quoting syntax to do
locale-specific translation of the characters between the double
quotes. The `-D', `--dump-strings', and `--dump-po-strings'
invocation options list the translatable strings found in a script
(see section 3.1.2.5 Locale-Specific Translation).
-
Bash implements the
!
keyword to negate the return value of
a pipeline (see section 3.2.2 Pipelines).
Very useful when an if
statement needs to act only if a test fails.
The Bash `-o pipefail' option to set
will cause a pipeline to
return a failure status if any command fails.
-
Bash has the
time
reserved word and command timing (see section 3.2.2 Pipelines).
The display of the timing statistics may be controlled with the
TIMEFORMAT
variable.
-
Bash implements the
for (( expr1 ; expr2 ; expr3 ))
arithmetic for command, similar to the C language (see section 3.2.4.1 Looping Constructs).
-
Bash includes the
select
compound command, which allows the
generation of simple menus (see section 3.2.4.2 Conditional Constructs).
-
Bash includes the
[[
compound command, which makes conditional
testing part of the shell grammar (see section 3.2.4.2 Conditional Constructs), including
optional regular expression matching.
-
Bash provides optional case-insensitive matching for the
case
and
[[
constructs.
-
Bash includes brace expansion (see section 3.5.1 Brace Expansion) and tilde
expansion (see section 3.5.2 Tilde Expansion).
-
Bash implements command aliases and the
alias
and unalias
builtins (see section 6.6 Aliases).
-
Bash provides shell arithmetic, the
((
compound command
(see section 3.2.4.2 Conditional Constructs),
and arithmetic expansion (see section 6.5 Shell Arithmetic).
-
Variables present in the shell's initial environment are automatically
exported to child processes. The Bourne shell does not normally do
this unless the variables are explicitly marked using the
export
command.
-
Bash supports the `+=' assignment operator, which appends to the value
of the variable named on the left hand side.
-
Bash includes the POSIX pattern removal `%', `#', `%%'
and `##' expansions to remove leading or trailing substrings from
variable values (see section 3.5.3 Shell Parameter Expansion).
-
The expansion
${#xx}
, which returns the length of ${xx}
,
is supported (see section 3.5.3 Shell Parameter Expansion).
-
The expansion
${var:
offset[:
length]}
,
which expands to the substring of var
's value of length
length, beginning at offset, is present
(see section 3.5.3 Shell Parameter Expansion).
-
The expansion
${var/[/]
pattern[/
replacement]}
,
which matches pattern and replaces it with replacement in
the value of var
, is available (see section 3.5.3 Shell Parameter Expansion).
-
The expansion
${!prefix*}
expansion, which expands to
the names of all shell variables whose names begin with prefix,
is available (see section 3.5.3 Shell Parameter Expansion).
-
Bash has indirect variable expansion using
${!word}
(see section 3.5.3 Shell Parameter Expansion).
-
Bash can expand positional parameters beyond
$9
using
${num}
.
-
The POSIX
$()
form of command substitution
is implemented (see section 3.5.4 Command Substitution),
and preferred to the Bourne shell's "
(which
is also implemented for backwards compatibility).
-
Bash has process substitution (see section 3.5.6 Process Substitution).
-
Bash automatically assigns variables that provide information about the
current user (
UID
, EUID
, and GROUPS
), the current host
(HOSTTYPE
, OSTYPE
, MACHTYPE
, and HOSTNAME
),
and the instance of Bash that is running (BASH
,
BASH_VERSION
, and BASH_VERSINFO
). See section 5.2 Bash Variables,
for details.
-
The
IFS
variable is used to split only the results of expansion,
not all words (see section 3.5.7 Word Splitting).
This closes a longstanding shell security hole.
-
The filename expansion bracket expression code uses `!' and `^'
to negate the set of characters between the brackets.
The Bourne shell uses only `!'.
-
Bash implements the full set of POSIX filename expansion operators,
including character classes, equivalence classes, and
collating symbols (see section 3.5.8 Filename Expansion).
-
Bash implements extended pattern matching features when the
extglob
shell option is enabled (see section 3.5.8.1 Pattern Matching).
-
It is possible to have a variable and a function with the same name;
sh
does not separate the two name spaces.
-
Bash functions are permitted to have local variables using the
local
builtin, and thus useful recursive functions may be written
(see section 4.2 Bash Builtin Commands).
-
Variable assignments preceding commands affect only that command, even
builtins and functions (see section 3.7.4 Environment).
In
sh
, all variable assignments
preceding commands are global unless the command is executed from the
file system.
-
Bash performs filename expansion on filenames specified as operands
to input and output redirection operators (see section 3.6 Redirections).
-
Bash contains the `<>' redirection operator, allowing a file to be
opened for both reading and writing, and the `&>' redirection
operator, for directing standard output and standard error to the same
file (see section 3.6 Redirections).
-
Bash includes the `<<<' redirection operator, allowing a string to
be used as the standard input to a command.
-
Bash implements the `[n]<&word' and `[n]>&word'
redirection operators, which move one file descriptor to another.
-
Bash treats a number of filenames specially when they are
used in redirection operators (see section 3.6 Redirections).
-
Bash can open network connections to arbitrary machines and services
with the redirection operators (see section 3.6 Redirections).
-
The
noclobber
option is available to avoid overwriting existing
files with output redirection (see section 4.3.1 The Set Builtin).
The `>|' redirection operator may be used to override noclobber
.
-
The Bash
cd
and pwd
builtins (see section 4.1 Bourne Shell Builtins)
each take `-L' and `-P' options to switch between logical and
physical modes.
-
Bash allows a function to override a builtin with the same name, and provides
access to that builtin's functionality within the function via the
builtin
and command
builtins (see section 4.2 Bash Builtin Commands).
-
The
command
builtin allows selective disabling of functions
when command lookup is performed (see section 4.2 Bash Builtin Commands).
-
Individual builtins may be enabled or disabled using the
enable
builtin (see section 4.2 Bash Builtin Commands).
-
The Bash
exec
builtin takes additional options that allow users
to control the contents of the environment passed to the executed
command, and what the zeroth argument to the command is to be
(see section 4.1 Bourne Shell Builtins).
-
Shell functions may be exported to children via the environment
using
export -f
(see section 3.3 Shell Functions).
-
The Bash
export
, readonly
, and declare
builtins can
take a `-f' option to act on shell functions, a `-p' option to
display variables with various attributes set in a format that can be
used as shell input, a `-n' option to remove various variable
attributes, and `name=value' arguments to set variable attributes
and values simultaneously.
-
The Bash
hash
builtin allows a name to be associated with
an arbitrary filename, even when that filename cannot be found by
searching the $PATH
, using `hash -p'
(see section 4.1 Bourne Shell Builtins).
-
Bash includes a
help
builtin for quick reference to shell
facilities (see section 4.2 Bash Builtin Commands).
-
The
printf
builtin is available to display formatted output
(see section 4.2 Bash Builtin Commands).
-
The Bash
read
builtin (see section 4.2 Bash Builtin Commands)
will read a line ending in `\' with
the `-r' option, and will use the REPLY
variable as a
default if no non-option arguments are supplied.
The Bash read
builtin
also accepts a prompt string with the `-p' option and will use
Readline to obtain the line when given the `-e' option.
The read
builtin also has additional options to control input:
the `-s' option will turn off echoing of input characters as
they are read, the `-t' option will allow read
to time out
if input does not arrive within a specified number of seconds, the
`-n' option will allow reading only a specified number of
characters rather than a full line, and the `-d' option will read
until a particular character rather than newline.
-
The
return
builtin may be used to abort execution of scripts
executed with the .
or source
builtins
(see section 4.1 Bourne Shell Builtins).
-
Bash includes the
shopt
builtin, for finer control of shell
optional capabilities (see section 4.3.2 The Shopt Builtin), and allows these options
to be set and unset at shell invocation (see section 6.1 Invoking Bash).
-
Bash has much more optional behavior controllable with the
set
builtin (see section 4.3.1 The Set Builtin).
-
The `-x' (`xtrace') option displays commands other than
simple commands when performing an execution trace
(see section 4.3.1 The Set Builtin).
-
The
test
builtin (see section 4.1 Bourne Shell Builtins)
is slightly different, as it implements the POSIX algorithm,
which specifies the behavior based on the number of arguments.
-
Bash includes the
caller
builtin, which displays the context of
any active subroutine call (a shell function or a script executed with
the .
or source
builtins). This supports the bash
debugger.
-
The
trap
builtin (see section 4.1 Bourne Shell Builtins) allows a
DEBUG
pseudo-signal specification, similar to EXIT
.
Commands specified with a DEBUG
trap are executed before every
simple command, for
command, case
command,
select
command, every arithmetic for
command, and before
the first command executes in a shell function.
The DEBUG
trap is not inherited by shell functions unless the
function has been given the trace
attribute or the
functrace
option has been enabled using the shopt
builtin.
The extdebug
shell option has additional effects on the
DEBUG
trap.
The trap
builtin (see section 4.1 Bourne Shell Builtins) allows an
ERR
pseudo-signal specification, similar to EXIT
and DEBUG
.
Commands specified with an ERR
trap are executed after a simple
command fails, with a few exceptions.
The ERR
trap is not inherited by shell functions unless the
-o errtrace
option to the set
builtin is enabled.
The trap
builtin (see section 4.1 Bourne Shell Builtins) allows a
RETURN
pseudo-signal specification, similar to
EXIT
and DEBUG
.
Commands specified with an RETURN
trap are executed before
execution resumes after a shell function or a shell script executed with
.
or source
returns.
The RETURN
trap is not inherited by shell functions unless the
function has been given the trace
attribute or the
functrace
option has been enabled using the shopt
builtin.
-
The Bash
type
builtin is more extensive and gives more information
about the names it finds (see section 4.2 Bash Builtin Commands).
-
The Bash
umask
builtin permits a `-p' option to cause
the output to be displayed in the form of a umask
command
that may be reused as input (see section 4.1 Bourne Shell Builtins).
-
Bash implements a
csh
-like directory stack, and provides the
pushd
, popd
, and dirs
builtins to manipulate it
(see section 6.8 The Directory Stack).
Bash also makes the directory stack visible as the value of the
DIRSTACK
shell variable.
-
Bash interprets special backslash-escaped characters in the prompt
strings when interactive (see section 6.9 Controlling the Prompt).
-
The Bash restricted mode is more useful (see section 6.10 The Restricted Shell);
the SVR4.2 shell restricted mode is too limited.
-
The
disown
builtin can remove a job from the internal shell
job table (see section 7.2 Job Control Builtins) or suppress the sending
of SIGHUP
to a job when the shell exits as the result of a
SIGHUP
.
-
Bash includes a number of features to support a separate debugger for
shell scripts.
-
The SVR4.2 shell has two privilege-related builtins
(
mldmode
and priv
) not present in Bash.
-
Bash does not have the
stop
or newgrp
builtins.
-
Bash does not use the
SHACCT
variable or perform shell accounting.
-
The SVR4.2
sh
uses a TIMEOUT
variable like Bash uses
TMOUT
.
More features unique to Bash may be found in 6. Bash Features.
B.1 Implementation Differences From The SVR4.2 Shell
Since Bash is a completely new implementation, it does not suffer from
many of the limitations of the SVR4.2 shell. For instance:
-
Bash does not fork a subshell when redirecting into or out of
a shell control structure such as an
if
or while
statement.
-
Bash does not allow unbalanced quotes. The SVR4.2 shell will silently
insert a needed closing quote at
EOF
under certain circumstances.
This can be the cause of some hard-to-find errors.
-
The SVR4.2 shell uses a baroque memory management scheme based on
trapping
SIGSEGV
. If the shell is started from a process with
SIGSEGV
blocked (e.g., by using the system()
C library
function call), it misbehaves badly.
-
In a questionable attempt at security, the SVR4.2 shell,
when invoked without the `-p' option, will alter its real
and effective UID and GID if they are less than some
magic threshold value, commonly 100.
This can lead to unexpected results.
-
The SVR4.2 shell does not allow users to trap
SIGSEGV
,
SIGALRM
, or SIGCHLD
.
-
The SVR4.2 shell does not allow the
IFS
, MAILCHECK
,
PATH
, PS1
, or PS2
variables to be unset.
-
The SVR4.2 shell treats `^' as the undocumented equivalent of
`|'.
-
Bash allows multiple option arguments when it is invoked (
-x -v
);
the SVR4.2 shell allows only one option argument (-xv
). In
fact, some versions of the shell dump core if the second argument begins
with a `-'.
-
The SVR4.2 shell exits a script if any builtin fails; Bash exits
a script only if one of the POSIX special builtins fails, and
only for certain failures, as enumerated in the POSIX standard.
-
The SVR4.2 shell behaves differently when invoked as
jsh
(it turns on job control).
C. GNU Free Documentation License
Version 1.3, 3 November 2008
| Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
http://fsf.org/
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
|
-
PREAMBLE
The purpose of this License is to make a manual, textbook, or other
functional and useful document free in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or noncommercially.
Secondarily, this License preserves for the author and publisher a way
to get credit for their work, while not being considered responsible
for modifications made by others.
This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense. It
complements the GNU General Public License, which is a copyleft
license designed for free software.
We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free
program should come with manuals providing the same freedoms that the
software does. But this License is not limited to software manuals;
it can be used for any textual work, regardless of subject matter or
whether it is published as a printed book. We recommend this License
principally for works whose purpose is instruction or reference.
-
APPLICABILITY AND DEFINITIONS
This License applies to any manual or other work, in any medium, that
contains a notice placed by the copyright holder saying it can be
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A "Modified Version" of the Document means any work containing the
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specific section name mentioned below, such as "Acknowledgements",
"Dedications", "Endorsements", or "History".) To "Preserve the Title"
of such a section when you modify the Document means that it remains a
section "Entitled XYZ" according to this definition.
The Document may include Warranty Disclaimers next to the notice which
states that this License applies to the Document. These Warranty
Disclaimers are considered to be included by reference in this
License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and has
no effect on the meaning of this License.
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VERBATIM COPYING
You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
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You may also lend copies, under the same conditions stated above, and
you may publicly display copies.
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COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly have
printed covers) of the Document, numbering more than 100, and the
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Copying with changes limited to the covers, as long as they preserve
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If the required texts for either cover are too voluminous to fit
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MODIFICATIONS
You may copy and distribute a Modified Version of the Document under
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and modification of the Modified Version to whoever possesses a copy
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Use in the Title Page (and on the covers, if any) a title distinct
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(which should, if there were any, be listed in the History section
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List on the Title Page, as authors, one or more persons or entities
responsible for authorship of the modifications in the Modified
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Document (all of its principal authors, if it has fewer than five),
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State on the Title page the name of the publisher of the
Modified Version, as the publisher.
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Preserve all the copyright notices of the Document.
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Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.
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Include, immediately after the copyright notices, a license notice
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Preserve in that license notice the full lists of Invariant Sections
and required Cover Texts given in the Document's license notice.
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Include an unaltered copy of this License.
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Preserve the section Entitled "History", Preserve its Title, and add
to it an item stating at least the title, year, new authors, and
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there is no section Entitled "History" in the Document, create one
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Preserve the network location, if any, given in the Document for
public access to a Transparent copy of the Document, and likewise
the network locations given in the Document for previous versions
it was based on. These may be placed in the "History" section.
You may omit a network location for a work that was published at
least four years before the Document itself, or if the original
publisher of the version it refers to gives permission.
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For any section Entitled "Acknowledgements" or "Dedications", Preserve
the Title of the section, and preserve in the section all the
substance and tone of each of the contributor acknowledgements and/or
dedications given therein.
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Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles. Section numbers
or the equivalent are not considered part of the section titles.
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Delete any section Entitled "Endorsements". Such a section
may not be included in the Modified Version.
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Do not retitle any existing section to be Entitled "Endorsements" or
to conflict in title with any Invariant Section.
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Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant. To do this, add their titles to the
list of Invariant Sections in the Modified Version's license notice.
These titles must be distinct from any other section titles.
You may add a section Entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various
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been approved by an organization as the authoritative definition of a
standard.
You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version. Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or
through arrangements made by) any one entity. If the Document already
includes a cover text for the same cover, previously added by you or
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you may not add another; but you may replace the old one, on explicit
permission from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.
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COMBINING DOCUMENTS
You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
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Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its
license notice, and that you preserve all their Warranty Disclaimers.
The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy. If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by
adding at the end of it, in parentheses, the name of the original
author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of
Invariant Sections in the license notice of the combined work.
In the combination, you must combine any sections Entitled "History"
in the various original documents, forming one section Entitled
"History"; likewise combine any sections Entitled "Acknowledgements",
and any sections Entitled "Dedications". You must delete all
sections Entitled "Endorsements."
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COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other documents
released under this License, and replace the individual copies of this
License in the various documents with a single copy that is included in
the collection, provided that you follow the rules of this License for
verbatim copying of each of the documents in all other respects.
You may extract a single document from such a collection, and distribute
it individually under this License, provided you insert a copy of this
License into the extracted document, and follow this License in all
other respects regarding verbatim copying of that document.
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AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, is called an "aggregate" if the copyright
resulting from the compilation is not used to limit the legal rights
of the compilation's users beyond what the individual works permit.
When the Document is included in an aggregate, this License does not
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If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half of
the entire aggregate, the Document's Cover Texts may be placed on
covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form.
Otherwise they must appear on printed covers that bracket the whole
aggregate.
-
TRANSLATION
Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections. You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also include
the original English version of this License and the original versions
of those notices and disclaimers. In case of a disagreement between
the translation and the original version of this License or a notice
or disclaimer, the original version will prevail.
If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to Preserve
its Title (section 1) will typically require changing the actual
title.
-
TERMINATION
You may not copy, modify, sublicense, or distribute the Document
except as expressly provided under this License. Any attempt
otherwise to copy, modify, sublicense, or distribute it is void, and
will automatically terminate your rights under this License.
However, if you cease all violation of this License, then your license
from a particular copyright holder is reinstated (a) provisionally,
unless and until the copyright holder explicitly and finally
terminates your license, and (b) permanently, if the copyright holder
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Moreover, your license from a particular copyright holder is
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violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from that
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your receipt of the notice.
Termination of your rights under this section does not terminate the
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this License. If your rights have been terminated and not permanently
reinstated, receipt of a copy of some or all of the same material does
not give you any rights to use it.
-
FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions
of the GNU Free Documentation License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns. See
http://www.gnu.org/copyleft/.
Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
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License can be used, that proxy's public statement of acceptance of a
version permanently authorizes you to choose that version for the
Document.
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RELICENSING
"Massive Multiauthor Collaboration Site" (or "MMC Site") means any
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"Massive Multiauthor Collaboration" (or "MMC") contained in the
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"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
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corporation with a principal place of business in San Francisco,
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"Incorporate" means to publish or republish a Document, in whole or
in part, as part of another Document.
An MMC is "eligible for relicensing" if it is licensed under this
License, and if all works that were first published under this License
somewhere other than this MMC, and subsequently incorporated in whole
or in part into the MMC, (1) had no cover texts or invariant sections,
and (2) were thus incorporated prior to November 1, 2008.
The operator of an MMC Site may republish an MMC contained in the site
under CC-BY-SA on the same site at any time before August 1, 2009,
provided the MMC is eligible for relicensing.
ADDENDUM: How to use this License for your documents
To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and
license notices just after the title page:
| Copyright (C) year your name.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
|
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the "with...Texts." line with this:
| with the Invariant Sections being list their titles, with
the Front-Cover Texts being list, and with the Back-Cover Texts
being list.
|
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License,
to permit their use in free software.
D. Indexes
D.1 Index of Shell Builtin Commands
D.2 Index of Shell Reserved Words
D.3 Parameter and Variable Index
D.4 Function Index
| Index Entry | Section |
|
A | | |
| abort (C-g) | 8.4.8 Some Miscellaneous Commands |
| abort (C-g) | 8.4.8 Some Miscellaneous Commands |
| accept-line (Newline or Return) | 8.4.2 Commands For Manipulating The History |
| accept-line (Newline or Return) | 8.4.2 Commands For Manipulating The History |
| alias-expand-line () | 8.4.8 Some Miscellaneous Commands |
| alias-expand-line () | 8.4.8 Some Miscellaneous Commands |
|
B | | |
| backward-char (C-b) | 8.4.1 Commands For Moving |
| backward-char (C-b) | 8.4.1 Commands For Moving |
| backward-delete-char (Rubout) | 8.4.3 Commands For Changing Text |
| backward-delete-char (Rubout) | 8.4.3 Commands For Changing Text |
| backward-kill-line (C-x Rubout) | 8.4.4 Killing And Yanking |
| backward-kill-line (C-x Rubout) | 8.4.4 Killing And Yanking |
| backward-kill-word (M-DEL) | 8.4.4 Killing And Yanking |
| backward-kill-word (M-DEL) | 8.4.4 Killing And Yanking |
| backward-word (M-b) | 8.4.1 Commands For Moving |
| backward-word (M-b) | 8.4.1 Commands For Moving |
| beginning-of-history (M-<) | 8.4.2 Commands For Manipulating The History |
| beginning-of-history (M-<) | 8.4.2 Commands For Manipulating The History |
| beginning-of-line (C-a) | 8.4.1 Commands For Moving |
| beginning-of-line (C-a) | 8.4.1 Commands For Moving |
|
C | | |
| call-last-kbd-macro (C-x e) | 8.4.7 Keyboard Macros |
| call-last-kbd-macro (C-x e) | 8.4.7 Keyboard Macros |
| capitalize-word (M-c) | 8.4.3 Commands For Changing Text |
| capitalize-word (M-c) | 8.4.3 Commands For Changing Text |
| character-search (C-]) | 8.4.8 Some Miscellaneous Commands |
| character-search (C-]) | 8.4.8 Some Miscellaneous Commands |
| character-search-backward (M-C-]) | 8.4.8 Some Miscellaneous Commands |
| character-search-backward (M-C-]) | 8.4.8 Some Miscellaneous Commands |
| clear-screen (C-l) | 8.4.1 Commands For Moving |
| clear-screen (C-l) | 8.4.1 Commands For Moving |
| complete (TAB) | 8.4.6 Letting Readline Type For You |
| complete (TAB) | 8.4.6 Letting Readline Type For You |
| complete-command (M-!) | 8.4.6 Letting Readline Type For You |
| complete-command (M-!) | 8.4.6 Letting Readline Type For You |
| complete-filename (M-/) | 8.4.6 Letting Readline Type For You |
| complete-filename (M-/) | 8.4.6 Letting Readline Type For You |
| complete-hostname (M-@) | 8.4.6 Letting Readline Type For You |
| complete-hostname (M-@) | 8.4.6 Letting Readline Type For You |
| complete-into-braces (M-{) | 8.4.6 Letting Readline Type For You |
| complete-into-braces (M-{) | 8.4.6 Letting Readline Type For You |
| complete-username (M-~) | 8.4.6 Letting Readline Type For You |
| complete-username (M-~) | 8.4.6 Letting Readline Type For You |
| complete-variable (M-$) | 8.4.6 Letting Readline Type For You |
| complete-variable (M-$) | 8.4.6 Letting Readline Type For You |
| copy-backward-word () | 8.4.4 Killing And Yanking |
| copy-backward-word () | 8.4.4 Killing And Yanking |
| copy-forward-word () | 8.4.4 Killing And Yanking |
| copy-forward-word () | 8.4.4 Killing And Yanking |
| copy-region-as-kill () | 8.4.4 Killing And Yanking |
| copy-region-as-kill () | 8.4.4 Killing And Yanking |
|
D | | |
| dabbrev-expand () | 8.4.6 Letting Readline Type For You |
| dabbrev-expand () | 8.4.6 Letting Readline Type For You |
| delete-char (C-d) | 8.4.3 Commands For Changing Text |
| delete-char (C-d) | 8.4.3 Commands For Changing Text |
| delete-char-or-list () | 8.4.6 Letting Readline Type For You |
| delete-char-or-list () | 8.4.6 Letting Readline Type For You |
| delete-horizontal-space () | 8.4.4 Killing And Yanking |
| delete-horizontal-space () | 8.4.4 Killing And Yanking |
| digit-argument (M-0, M-1, <small>...</small> M--) | 8.4.5 Specifying Numeric Arguments |
| digit-argument (M-0, M-1, <small>...</small> M--) | 8.4.5 Specifying Numeric Arguments |
| display-shell-version (C-x C-v) | 8.4.8 Some Miscellaneous Commands |
| display-shell-version (C-x C-v) | 8.4.8 Some Miscellaneous Commands |
| do-uppercase-version (M-a, M-b, M-x, <small>...</small>) | 8.4.8 Some Miscellaneous Commands |
| do-uppercase-version (M-a, M-b, M-x, <small>...</small>) | 8.4.8 Some Miscellaneous Commands |
| downcase-word (M-l) | 8.4.3 Commands For Changing Text |
| downcase-word (M-l) | 8.4.3 Commands For Changing Text |
| dump-functions () | 8.4.8 Some Miscellaneous Commands |
| dump-functions () | 8.4.8 Some Miscellaneous Commands |
| dump-macros () | 8.4.8 Some Miscellaneous Commands |
| dump-macros () | 8.4.8 Some Miscellaneous Commands |
| dump-variables () | 8.4.8 Some Miscellaneous Commands |
| dump-variables () | 8.4.8 Some Miscellaneous Commands |
| dynamic-complete-history (M-TAB) | 8.4.6 Letting Readline Type For You |
| dynamic-complete-history (M-TAB) | 8.4.6 Letting Readline Type For You |
|
E | | |
| edit-and-execute-command (C-xC-e) | 8.4.8 Some Miscellaneous Commands |
| edit-and-execute-command (C-xC-e) | 8.4.8 Some Miscellaneous Commands |
| end-kbd-macro (C-x )) | 8.4.7 Keyboard Macros |
| end-kbd-macro (C-x )) | 8.4.7 Keyboard Macros |
| end-of-file (usually C-d) | 8.4.3 Commands For Changing Text |
| end-of-file (usually C-d) | 8.4.3 Commands For Changing Text |
| end-of-history (M->) | 8.4.2 Commands For Manipulating The History |
| end-of-history (M->) | 8.4.2 Commands For Manipulating The History |
| end-of-line (C-e) | 8.4.1 Commands For Moving |
| end-of-line (C-e) | 8.4.1 Commands For Moving |
| exchange-point-and-mark (C-x C-x) | 8.4.8 Some Miscellaneous Commands |
| exchange-point-and-mark (C-x C-x) | 8.4.8 Some Miscellaneous Commands |
|
F | | |
| forward-backward-delete-char () | 8.4.3 Commands For Changing Text |
| forward-backward-delete-char () | 8.4.3 Commands For Changing Text |
| forward-char (C-f) | 8.4.1 Commands For Moving |
| forward-char (C-f) | 8.4.1 Commands For Moving |
| forward-search-history (C-s) | 8.4.2 Commands For Manipulating The History |
| forward-search-history (C-s) | 8.4.2 Commands For Manipulating The History |
| forward-word (M-f) | 8.4.1 Commands For Moving |
| forward-word (M-f) | 8.4.1 Commands For Moving |
|
G | | |
| glob-complete-word (M-g) | 8.4.8 Some Miscellaneous Commands |
| glob-complete-word (M-g) | 8.4.8 Some Miscellaneous Commands |
| glob-expand-word (C-x *) | 8.4.8 Some Miscellaneous Commands |
| glob-expand-word (C-x *) | 8.4.8 Some Miscellaneous Commands |
| glob-list-expansions (C-x g) | 8.4.8 Some Miscellaneous Commands |
| glob-list-expansions (C-x g) | 8.4.8 Some Miscellaneous Commands |
|
H | | |
| history-and-alias-expand-line () | 8.4.8 Some Miscellaneous Commands |
| history-and-alias-expand-line () | 8.4.8 Some Miscellaneous Commands |
| history-expand-line (M-^) | 8.4.8 Some Miscellaneous Commands |
| history-expand-line (M-^) | 8.4.8 Some Miscellaneous Commands |
| history-search-backward () | 8.4.2 Commands For Manipulating The History |
| history-search-backward () | 8.4.2 Commands For Manipulating The History |
| history-search-forward () | 8.4.2 Commands For Manipulating The History |
| history-search-forward () | 8.4.2 Commands For Manipulating The History |
| history-substr-search-backward () | 8.4.2 Commands For Manipulating The History |
| history-substr-search-backward () | 8.4.2 Commands For Manipulating The History |
| history-substr-search-forward () | 8.4.2 Commands For Manipulating The History |
| history-substr-search-forward () | 8.4.2 Commands For Manipulating The History |
|
I | | |
| insert-comment (M-#) | 8.4.8 Some Miscellaneous Commands |
| insert-comment (M-#) | 8.4.8 Some Miscellaneous Commands |
| insert-completions (M-*) | 8.4.6 Letting Readline Type For You |
| insert-completions (M-*) | 8.4.6 Letting Readline Type For You |
| insert-last-argument (M-. or M-_) | 8.4.8 Some Miscellaneous Commands |
| insert-last-argument (M-. or M-_) | 8.4.8 Some Miscellaneous Commands |
|
K | | |
| kill-line (C-k) | 8.4.4 Killing And Yanking |
| kill-line (C-k) | 8.4.4 Killing And Yanking |
| kill-region () | 8.4.4 Killing And Yanking |
| kill-region () | 8.4.4 Killing And Yanking |
| kill-whole-line () | 8.4.4 Killing And Yanking |
| kill-whole-line () | 8.4.4 Killing And Yanking |
| kill-word (M-d) | 8.4.4 Killing And Yanking |
| kill-word (M-d) | 8.4.4 Killing And Yanking |
|
M | | |
| magic-space () | 8.4.8 Some Miscellaneous Commands |
| magic-space () | 8.4.8 Some Miscellaneous Commands |
| menu-complete () | 8.4.6 Letting Readline Type For You |
| menu-complete () | 8.4.6 Letting Readline Type For You |
| menu-complete-backward () | 8.4.6 Letting Readline Type For You |
| menu-complete-backward () | 8.4.6 Letting Readline Type For You |
|
N | | |
| next-history (C-n) | 8.4.2 Commands For Manipulating The History |
| next-history (C-n) | 8.4.2 Commands For Manipulating The History |
| non-incremental-forward-search-history (M-n) | 8.4.2 Commands For Manipulating The History |
| non-incremental-forward-search-history (M-n) | 8.4.2 Commands For Manipulating The History |
| non-incremental-reverse-search-history (M-p) | 8.4.2 Commands For Manipulating The History |
| non-incremental-reverse-search-history (M-p) | 8.4.2 Commands For Manipulating The History |
|
O | | |
| operate-and-get-next (C-o) | 8.4.8 Some Miscellaneous Commands |
| operate-and-get-next (C-o) | 8.4.8 Some Miscellaneous Commands |
| overwrite-mode () | 8.4.3 Commands For Changing Text |
| overwrite-mode () | 8.4.3 Commands For Changing Text |
|
P | | |
| possible-command-completions (C-x !) | 8.4.6 Letting Readline Type For You |
| possible-command-completions (C-x !) | 8.4.6 Letting Readline Type For You |
| possible-completions (M-?) | 8.4.6 Letting Readline Type For You |
| possible-completions (M-?) | 8.4.6 Letting Readline Type For You |
| possible-filename-completions (C-x /) | 8.4.6 Letting Readline Type For You |
| possible-filename-completions (C-x /) | 8.4.6 Letting Readline Type For You |
| possible-hostname-completions (C-x @) | 8.4.6 Letting Readline Type For You |
| possible-hostname-completions (C-x @) | 8.4.6 Letting Readline Type For You |
| possible-username-completions (C-x ~) | 8.4.6 Letting Readline Type For You |
| possible-username-completions (C-x ~) | 8.4.6 Letting Readline Type For You |
| possible-variable-completions (C-x $) | 8.4.6 Letting Readline Type For You |
| possible-variable-completions (C-x $) | 8.4.6 Letting Readline Type For You |
| prefix-meta (ESC) | 8.4.8 Some Miscellaneous Commands |
| prefix-meta (ESC) | 8.4.8 Some Miscellaneous Commands |
| previous-history (C-p) | 8.4.2 Commands For Manipulating The History |
| previous-history (C-p) | 8.4.2 Commands For Manipulating The History |
| print-last-kbd-macro () | 8.4.7 Keyboard Macros |
| print-last-kbd-macro () | 8.4.7 Keyboard Macros |
|
Q | | |
| quoted-insert (C-q or C-v) | 8.4.3 Commands For Changing Text |
| quoted-insert (C-q or C-v) | 8.4.3 Commands For Changing Text |
|
R | | |
| re-read-init-file (C-x C-r) | 8.4.8 Some Miscellaneous Commands |
| re-read-init-file (C-x C-r) | 8.4.8 Some Miscellaneous Commands |
| redraw-current-line () | 8.4.1 Commands For Moving |
| redraw-current-line () | 8.4.1 Commands For Moving |
| reverse-search-history (C-r) | 8.4.2 Commands For Manipulating The History |
| reverse-search-history (C-r) | 8.4.2 Commands For Manipulating The History |
| revert-line (M-r) | 8.4.8 Some Miscellaneous Commands |
| revert-line (M-r) | 8.4.8 Some Miscellaneous Commands |
|
S | | |
| self-insert (a, b, A, 1, !, <small>...</small>) | 8.4.3 Commands For Changing Text |
| self-insert (a, b, A, 1, !, <small>...</small>) | 8.4.3 Commands For Changing Text |
| set-mark (C-@) | 8.4.8 Some Miscellaneous Commands |
| set-mark (C-@) | 8.4.8 Some Miscellaneous Commands |
| shell-backward-kill-word () | 8.4.4 Killing And Yanking |
| shell-backward-kill-word () | 8.4.4 Killing And Yanking |
| shell-backward-word () | 8.4.1 Commands For Moving |
| shell-backward-word () | 8.4.1 Commands For Moving |
| shell-expand-line (M-C-e) | 8.4.8 Some Miscellaneous Commands |
| shell-expand-line (M-C-e) | 8.4.8 Some Miscellaneous Commands |
| shell-forward-word () | 8.4.1 Commands For Moving |
| shell-forward-word () | 8.4.1 Commands For Moving |
| shell-kill-word () | 8.4.4 Killing And Yanking |
| shell-kill-word () | 8.4.4 Killing And Yanking |
| skip-csi-sequence () | 8.4.8 Some Miscellaneous Commands |
| skip-csi-sequence () | 8.4.8 Some Miscellaneous Commands |
| start-kbd-macro (C-x () | 8.4.7 Keyboard Macros |
| start-kbd-macro (C-x () | 8.4.7 Keyboard Macros |
|
T | | |
| tilde-expand (M-&) | 8.4.8 Some Miscellaneous Commands |
| tilde-expand (M-&) | 8.4.8 Some Miscellaneous Commands |
| transpose-chars (C-t) | 8.4.3 Commands For Changing Text |
| transpose-chars (C-t) | 8.4.3 Commands For Changing Text |
| transpose-words (M-t) | 8.4.3 Commands For Changing Text |
| transpose-words (M-t) | 8.4.3 Commands For Changing Text |
|
U | | |
| undo (C-_ or C-x C-u) | 8.4.8 Some Miscellaneous Commands |
| undo (C-_ or C-x C-u) | 8.4.8 Some Miscellaneous Commands |
| universal-argument () | 8.4.5 Specifying Numeric Arguments |
| universal-argument () | 8.4.5 Specifying Numeric Arguments |
| unix-filename-rubout () | 8.4.4 Killing And Yanking |
| unix-filename-rubout () | 8.4.4 Killing And Yanking |
| unix-line-discard (C-u) | 8.4.4 Killing And Yanking |
| unix-line-discard (C-u) | 8.4.4 Killing And Yanking |
| unix-word-rubout (C-w) | 8.4.4 Killing And Yanking |
| unix-word-rubout (C-w) | 8.4.4 Killing And Yanking |
| upcase-word (M-u) | 8.4.3 Commands For Changing Text |
| upcase-word (M-u) | 8.4.3 Commands For Changing Text |
|
Y | | |
| yank (C-y) | 8.4.4 Killing And Yanking |
| yank (C-y) | 8.4.4 Killing And Yanking |
| yank-last-arg (M-. or M-_) | 8.4.2 Commands For Manipulating The History |
| yank-last-arg (M-. or M-_) | 8.4.2 Commands For Manipulating The History |
| yank-nth-arg (M-C-y) | 8.4.2 Commands For Manipulating The History |
| yank-nth-arg (M-C-y) | 8.4.2 Commands For Manipulating The History |
| yank-pop (M-y) | 8.4.4 Killing And Yanking |
| yank-pop (M-y) | 8.4.4 Killing And Yanking |
|
D.5 Concept Index
| Index Entry | Section |
|
A | | |
| alias expansion | 6.6 Aliases |
| arithmetic evaluation | 6.5 Shell Arithmetic |
| arithmetic expansion | 3.5.5 Arithmetic Expansion |
| arithmetic, shell | 6.5 Shell Arithmetic |
| arrays | 6.7 Arrays |
|
B | | |
| background | 7.1 Job Control Basics |
| Bash configuration | 10.1 Basic Installation |
| Bash installation | 10.1 Basic Installation |
| Bourne shell | 3. Basic Shell Features |
| brace expansion | 3.5.1 Brace Expansion |
| builtin | 2. Definitions |
|
C | | |
| command editing | 8.2.1 Readline Bare Essentials |
| command execution | 3.7.2 Command Search and Execution |
| command expansion | 3.7.1 Simple Command Expansion |
| command history | 9.1 Bash History Facilities |
| command search | 3.7.2 Command Search and Execution |
| command substitution | 3.5.4 Command Substitution |
| command timing | 3.2.2 Pipelines |
| commands, compound | 3.2.4 Compound Commands |
| commands, conditional | 3.2.4.2 Conditional Constructs |
| commands, grouping | 3.2.4.3 Grouping Commands |
| commands, lists | 3.2.3 Lists of Commands |
| commands, looping | 3.2.4.1 Looping Constructs |
| commands, pipelines | 3.2.2 Pipelines |
| commands, shell | 3.2 Shell Commands |
| commands, simple | 3.2.1 Simple Commands |
| comments, shell | 3.1.3 Comments |
| completion builtins | 8.7 Programmable Completion Builtins |
| configuration | 10.1 Basic Installation |
| control operator | 2. Definitions |
| coprocess | 3.2.5 Coprocesses |
|
D | | |
| directory stack | 6.8 The Directory Stack |
|
E | | |
| editing command lines | 8.2.1 Readline Bare Essentials |
| environment | 3.7.4 Environment |
| evaluation, arithmetic | 6.5 Shell Arithmetic |
| event designators | 9.3.1 Event Designators |
| execution environment | 3.7.3 Command Execution Environment |
| exit status | 2. Definitions |
| exit status | 3.7.5 Exit Status |
| expansion | 3.5 Shell Expansions |
| expansion, arithmetic | 3.5.5 Arithmetic Expansion |
| expansion, brace | 3.5.1 Brace Expansion |
| expansion, filename | 3.5.8 Filename Expansion |
| expansion, parameter | 3.5.3 Shell Parameter Expansion |
| expansion, pathname | 3.5.8 Filename Expansion |
| expansion, tilde | 3.5.2 Tilde Expansion |
| expressions, arithmetic | 6.5 Shell Arithmetic |
| expressions, conditional | 6.4 Bash Conditional Expressions |
|
F | | |
| field | 2. Definitions |
| filename | 2. Definitions |
| filename expansion | 3.5.8 Filename Expansion |
| foreground | 7.1 Job Control Basics |
| functions, shell | 3.3 Shell Functions |
|
H | | |
| history builtins | 9.2 Bash History Builtins |
| history events | 9.3.1 Event Designators |
| history expansion | 9.3 History Expansion |
| history list | 9.1 Bash History Facilities |
| History, how to use | 8.8 A Programmable Completion Example |
|
I | | |
| identifier | 2. Definitions |
| initialization file, readline | 8.3 Readline Init File |
| installation | 10.1 Basic Installation |
| interaction, readline | 8.2 Readline Interaction |
| interactive shell | 6.1 Invoking Bash |
| interactive shell | 6.3 Interactive Shells |
| internationalization | 3.1.2.5 Locale-Specific Translation |
|
J | | |
| job | 2. Definitions |
| job control | 2. Definitions |
| job control | 7.1 Job Control Basics |
|
K | | |
| kill ring | 8.2.3 Readline Killing Commands |
| killing text | 8.2.3 Readline Killing Commands |
|
L | | |
| localization | 3.1.2.5 Locale-Specific Translation |
| login shell | 6.1 Invoking Bash |
|
M | | |
| matching, pattern | 3.5.8.1 Pattern Matching |
| metacharacter | 2. Definitions |
|
N | | |
| name | 2. Definitions |
| native languages | 3.1.2.5 Locale-Specific Translation |
| notation, readline | 8.2.1 Readline Bare Essentials |
|
O | | |
| operator, shell | 2. Definitions |
|
P | | |
| parameter expansion | 3.5.3 Shell Parameter Expansion |
| parameters | 3.4 Shell Parameters |
| parameters, positional | 3.4.1 Positional Parameters |
| parameters, special | 3.4.2 Special Parameters |
| pathname expansion | 3.5.8 Filename Expansion |
| pattern matching | 3.5.8.1 Pattern Matching |
| pipeline | 3.2.2 Pipelines |
| POSIX | 2. Definitions |
| POSIX Mode | 6.11 Bash POSIX Mode |
| process group | 2. Definitions |
| process group ID | 2. Definitions |
| process substitution | 3.5.6 Process Substitution |
| programmable completion | 8.6 Programmable Completion |
| prompting | 6.9 Controlling the Prompt |
|
Q | | |
| quoting | 3.1.2 Quoting |
| quoting, ANSI | 3.1.2.4 ANSI-C Quoting |
|
R | | |
| Readline, how to use | 7.3 Job Control Variables |
| redirection | 3.6 Redirections |
| reserved word | 2. Definitions |
| restricted shell | 6.10 The Restricted Shell |
| return status | 2. Definitions |
|
S | | |
| shell arithmetic | 6.5 Shell Arithmetic |
| shell function | 3.3 Shell Functions |
| shell script | 3.8 Shell Scripts |
| shell variable | 3.4 Shell Parameters |
| shell, interactive | 6.3 Interactive Shells |
| signal | 2. Definitions |
| signal handling | 3.7.6 Signals |
| special builtin | 2. Definitions |
| special builtin | 4.4 Special Builtins |
| startup files | 6.2 Bash Startup Files |
| suspending jobs | 7.1 Job Control Basics |
|
T | | |
| tilde expansion | 3.5.2 Tilde Expansion |
| token | 2. Definitions |
| translation, native languages | 3.1.2.5 Locale-Specific Translation |
|
V | | |
| variable, shell | 3.4 Shell Parameters |
| variables, readline | 8.3.1 Readline Init File Syntax |
|
W | | |
| word | 2. Definitions |
| word splitting | 3.5.7 Word Splitting |
|
Y | | |
| yanking text | 8.2.3 Readline Killing Commands |
|
Table of Contents
Short Table of Contents
1. Introduction
2. Definitions
3. Basic Shell Features
4. Shell Builtin Commands
5. Shell Variables
6. Bash Features
7. Job Control
8. Command Line Editing
9. Using History Interactively
10. Installing Bash
A. Reporting Bugs
B. Major Differences From The Bourne Shell
C. GNU Free Documentation License
D. Indexes
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0707010007eb39000081a40000000000000000000000015428b73500000eff00000100000100b5ffffffffffffffff0000002500000000root/usr/local/share/doc/bash/README Introduction
============
This is GNU Bash, version 4.3. Bash is the GNU Project's Bourne
Again SHell, a complete implementation of the POSIX shell spec,
but also with interactive command line editing, job control on
architectures that support it, csh-like features such as history
substitution and brace expansion, and a slew of other features.
For more information on the features of Bash that are new to this
type of shell, see the file `doc/bashref.texi'. There is also a
large Unix-style man page. The man page is the definitive description
of the shell's features.
See the file POSIX for a discussion of how the Bash defaults differ
from the POSIX spec and a description of the Bash `posix mode'.
There are some user-visible incompatibilities between this version
of Bash and previous widely-distributed versions, bash-4.1 and
bash-4.2. For details, see the file COMPAT. The NEWS file tersely
lists features that are new in this release.
Bash is free software, distributed under the terms of the [GNU] General
Public License as published by the Free Software Foundation,
version 3 of the License (or any later version). For more information,
see the file COPYING.
A number of frequently-asked questions are answered in the file
`doc/FAQ'.
To compile Bash, type `./configure', then `make'. Bash auto-configures
the build process, so no further intervention should be necessary. Bash
builds with `gcc' by default if it is available. If you want to use `cc'
instead, type
CC=cc ./configure
if you are using a Bourne-style shell. If you are not, the following
may work:
env CC=cc ./configure
Read the file INSTALL in this directory for more information about how
to customize and control the build process. The file NOTES contains
platform-specific installation and configuration information.
If you are a csh user and wish to convert your csh aliases to Bash
aliases, you may wish to use the script `examples/misc/alias-conv.sh'
as a starting point. The script `examples/misc/cshtobash' is a
more ambitious script that attempts to do a more complete job.
Reporting Bugs
==============
Bug reports for bash should be sent to:
bug-bash@gnu.org
using the `bashbug' program that is built and installed at the same
time as bash.
The discussion list `bug-bash@gnu.org' often contains information
about new ports of Bash, or discussions of new features or behavior
changes that people would like. This mailing list is also available
as a usenet newsgroup: gnu.bash.bug.
When you send a bug report, please use the `bashbug' program that is
built at the same time as bash. If bash fails to build, try building
bashbug directly with `make bashbug'. If you cannot build `bashbug',
please send mail to bug-bash@gnu.org with the following information:
* the version number and release status of Bash (e.g., 2.05a-release)
* the machine and OS that it is running on (you may run
`bashversion -l' from the bash build directory for this information)
* a list of the compilation flags or the contents of `config.h', if
appropriate
* a description of the bug
* a recipe for recreating the bug reliably
* a fix for the bug if you have one!
The `bashbug' program includes much of this automatically.
Questions and requests for help with bash and bash programming may be
sent to the help-bash@gnu.org mailing list.
If you would like to contact the Bash maintainers directly, send mail
to bash-maintainers@gnu.org.
While the Bash maintainers do not promise to fix all bugs, we would
like this shell to be the best that we can make it.
Enjoy!
Chet Ramey
chet.ramey@case.edu
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved. This file is offered as-is,
without any warranty.
0707010007eb33000081a40000000000000000000000015428b73500004a3800000100000100b5ffffffffffffffff0000002500000000root/usr/local/share/doc/bash/COMPAT Compatibility with previous versions
====================================
This document details the incompatibilities between this version of bash,
bash-4.3, and the previous widely-available versions, bash-3.x (which is
still the `standard' version for Mac OS X), 4.0/4.1 (which are still
standard on a few Linux distributions), and bash-4.2, the current
widely-available version. These were discovered by users of bash-2.x
through 4.x, so this list is not comprehensive. Some of these
incompatibilities occur between the current version and versions 2.0 and
above.
1. Bash uses a new quoting syntax, $"...", to do locale-specific
string translation. Users who have relied on the (undocumented)
behavior of bash-1.14 will have to change their scripts. For
instance, if you are doing something like this to get the value of
a variable whose name is the value of a second variable:
eval var2=$"$var1"
you will have to change to a different syntax.
This capability is directly supported by bash-2.0:
var2=${!var1}
This alternate syntax will work portably between bash-1.14 and bash-2.0:
eval var2=\$${var1}
2. One of the bugs fixed in the YACC grammar tightens up the rules
concerning group commands ( {...} ). The `list' that composes the
body of the group command must be terminated by a newline or
semicolon. That's because the braces are reserved words, and are
recognized as such only when a reserved word is legal. This means
that while bash-1.14 accepted shell function definitions like this:
foo() { : }
bash-2.0 requires this:
foo() { :; }
This is also an issue for commands like this:
mkdir dir || { echo 'could not mkdir' ; exit 1; }
The syntax required by bash-2.0 is also accepted by bash-1.14.
3. The options to `bind' have changed to make them more consistent with
the rest of the bash builtins. If you are using `bind -d' to list
the readline key bindings in a form that can be re-read, use `bind -p'
instead. If you were using `bind -v' to list the key bindings, use
`bind -P' instead.
4. The `long' invocation options must now be prefixed by `--' instead
of `-'. (The old form is still accepted, for the time being.)
5. There was a bug in the version of readline distributed with bash-1.14
that caused it to write badly-formatted key bindings when using
`bind -d'. The only key sequences that were affected are C-\ (which
should appear as \C-\\ in a key binding) and C-" (which should appear
as \C-\"). If these key sequences appear in your inputrc, as, for
example,
"\C-\": self-insert
they will need to be changed to something like the following:
"\C-\\": self-insert
6. A number of people complained about having to use ESC to terminate an
incremental search, and asked for an alternate mechanism. Bash-2.03
uses the value of the settable readline variable `isearch-terminators'
to decide which characters should terminate an incremental search. If
that variable has not been set, ESC and Control-J will terminate a
search.
7. Some variables have been removed: MAIL_WARNING, notify, history_control,
command_oriented_history, glob_dot_filenames, allow_null_glob_expansion,
nolinks, hostname_completion_file, noclobber, no_exit_on_failed_exec, and
cdable_vars. Most of them are now implemented with the new `shopt'
builtin; others were already implemented by `set'. Here is a list of
correspondences:
MAIL_WARNING shopt mailwarn
notify set -o notify
history_control HISTCONTROL
command_oriented_history shopt cmdhist
glob_dot_filenames shopt dotglob
allow_null_glob_expansion shopt nullglob
nolinks set -o physical
hostname_completion_file HOSTFILE
noclobber set -o noclobber
no_exit_on_failed_exec shopt execfail
cdable_vars shopt cdable_vars
8. `ulimit' now sets both hard and soft limits and reports the soft limit
by default (when neither -H nor -S is specified). This is compatible
with versions of sh and ksh that implement `ulimit'. The bash-1.14
behavior of, for example,
ulimit -c 0
can be obtained with
ulimit -S -c 0
It may be useful to define an alias:
alias ulimit="ulimit -S"
9. Bash-2.01 uses a new quoting syntax, $'...' to do ANSI-C string
translation. Backslash-escaped characters in ... are expanded and
replaced as specified by the ANSI C standard.
10. The sourcing of startup files has changed somewhat. This is explained
more completely in the INVOCATION section of the manual page.
A non-interactive shell not named `sh' and not in posix mode reads
and executes commands from the file named by $BASH_ENV. A
non-interactive shell started by `su' and not in posix mode will read
startup files. No other non-interactive shells read any startup files.
An interactive shell started in posix mode reads and executes commands
from the file named by $ENV.
11. The <> redirection operator was changed to conform to the POSIX.2 spec.
In the absence of any file descriptor specification preceding the `<>',
file descriptor 0 is used. In bash-1.14, this was the behavior only
when in POSIX mode. The bash-1.14 behavior may be obtained with
<>filename 1>&0
12. The `alias' builtin now checks for invalid options and takes a `-p'
option to display output in POSIX mode. If you have old aliases beginning
with `-' or `+', you will have to add the `--' to the alias command
that declares them:
alias -x='chmod a-x' --> alias -- -x='chmod a-x'
13. The behavior of range specificiers within bracket matching expressions
in the pattern matcher (e.g., [A-Z]) depends on the current locale,
specifically the value of the LC_COLLATE environment variable. Setting
this variable to C or POSIX will result in the traditional ASCII behavior
for range comparisons. If the locale is set to something else, e.g.,
en_US (specified by the LANG or LC_ALL variables), collation order is
locale-dependent. For example, the en_US locale sorts the upper and
lower case letters like this:
AaBb...Zz
so a range specification like [A-Z] will match every letter except `z'.
Other locales collate like
aAbBcC...zZ
which means that [A-Z] matches every letter except `a'.
The portable way to specify upper case letters is [:upper:] instead of
A-Z; lower case may be specified as [:lower:] instead of a-z.
Look at the manual pages for setlocale(3), strcoll(3), and, if it is
present, locale(1).
You can find your current locale information by running locale(1):
caleb.ins.cwru.edu(2)$ locale
LANG=en_US
LC_CTYPE="en_US"
LC_NUMERIC="en_US"
LC_TIME="en_US"
LC_COLLATE="en_US"
LC_MONETARY="en_US"
LC_MESSAGES="en_US"
LC_ALL=en_US
My advice is to put
export LC_COLLATE=C
into /etc/profile and inspect any shell scripts run from cron for
constructs like [A-Z]. This will prevent things like
rm [A-Z]*
from removing every file in the current directory except those beginning
with `z' and still allow individual users to change the collation order.
Users may put the above command into their own profiles as well, of course.
14. Bash versions up to 1.14.7 included an undocumented `-l' operator to
the `test/[' builtin. It was a unary operator that expanded to the
length of its string argument. This let you do things like
test -l $variable -lt 20
for example.
This was included for backwards compatibility with old versions of the
Bourne shell, which did not provide an easy way to obtain the length of
the value of a shell variable.
This operator is not part of the POSIX standard, because one can (and
should) use ${#variable} to get the length of a variable's value.
Bash-2.x does not support it.
15. Bash no longer auto-exports the HOME, PATH, SHELL, TERM, HOSTNAME,
HOSTTYPE, MACHTYPE, or OSTYPE variables. If they appear in the initial
environment, the export attribute will be set, but if bash provides a
default value, they will remain local to the current shell.
16. Bash no longer initializes the FUNCNAME, GROUPS, or DIRSTACK variables
to have special behavior if they appear in the initial environment.
17. Bash no longer removes the export attribute from the SSH_CLIENT or
SSH2_CLIENT variables, and no longer attempts to discover whether or
not it has been invoked by sshd in order to run the startup files.
18. Bash no longer requires that the body of a function be a group command;
any compound command is accepted.
19. As of bash-3.0, the pattern substitution operators no longer perform
quote removal on the pattern before attempting the match. This is the
way the pattern removal functions behave, and is more consistent.
20. After bash-3.0 was released, I reimplemented tilde expansion, incorporating
it into the mainline word expansion code. This fixes the bug that caused
the results of tilde expansion to be re-expanded. There is one
incompatibility: a ${paramOPword} expansion within double quotes will not
perform tilde expansion on WORD. This is consistent with the other
expansions, and what POSIX specifies.
21. A number of variables have the integer attribute by default, so the +=
assignment operator returns expected results: RANDOM, LINENO, MAILCHECK,
HISTCMD, OPTIND.
22. Bash-3.x is much stricter about $LINENO correctly reflecting the line
number in a script; assignments to LINENO have little effect.
23. By default, readline binds the terminal special characters to their
readline equivalents. As of bash-3.1/readline-5.1, this is optional and
controlled by the bind-tty-special-chars readline variable.
24. The \W prompt string expansion abbreviates $HOME as `~'. The previous
behavior is available with ${PWD##/*/}.
25. The arithmetic exponentiation operator is right-associative as of bash-3.1.
26. The rules concerning valid alias names are stricter, as per POSIX.2.
27. The Readline key binding functions now obey the convert-meta setting active
when the binding takes place, as the dispatch code does when characters
are read and processed.
28. The historical behavior of `trap' reverting signal disposition to the
original handling in the absence of a valid first argument is implemented
only if the first argument is a valid signal number.
29. In versions of bash after 3.1, the ${parameter//pattern/replacement}
expansion does not interpret `%' or `#' specially. Those anchors don't
have any real meaning when replacing every match.
30. Beginning with bash-3.1, the combination of posix mode and enabling the
`xpg_echo' option causes echo to ignore all options, not looking for `-n'
31. Beginning with bash-3.2, bash follows the Bourne-shell-style (and POSIX-
style) rules for parsing the contents of old-style backquoted command
substitutions. Previous versions of bash attempted to recursively parse
embedded quoted strings and shell constructs; bash-3.2 uses strict POSIX
rules to find the closing backquote and simply passes the contents of the
command substitution to a subshell for parsing and execution.
32. Beginning with bash-3.2, bash uses access(2) when executing primaries for
the test builtin and the [[ compound command, rather than looking at the
file permission bits obtained with stat(2). This obeys restrictions of
the file system (e.g., read-only or noexec mounts) not available via stat.
33. Bash-3.2 adopts the convention used by other string and pattern matching
operators for the `[[' compound command, and matches any quoted portion
of the right-hand-side argument to the =~ operator as a string rather
than a regular expression.
34. Bash-4.0 allows the behavior in the previous item to be modified using
the notion of a shell `compatibility level'. If the compat31 shopt
option is set, quoting the pattern has no special effect.
35. Bash-3.2 (patched) and Bash-4.0 fix a bug that leaves the shell in an
inconsistent internal state following an assignment error. One of the
changes means that compound commands or { ... } grouping commands are
aborted under some circumstances in which they previously were not.
This is what Posix specifies.
36. Bash-4.0 now allows process substitution constructs to pass unchanged
through brace expansion, so any expansion of the contents will have to be
separately specified, and each process subsitution will have to be
separately entered.
37. Bash-4.0 now allows SIGCHLD to interrupt the wait builtin, as Posix
specifies, so the SIGCHLD trap is no longer always invoked once per
exiting child if you are using `wait' to wait for all children. As
of bash-4.2, this is the status quo only when in posix mode.
38. Since bash-4.0 now follows Posix rules for finding the closing delimiter
of a $() command substitution, it will not behave as previous versions
did, but will catch more syntax and parsing errors before spawning a
subshell to evaluate the command substitution.
39. The programmable completion code uses the same set of delimiting characters
as readline when breaking the command line into words, rather than the
set of shell metacharacters, so programmable completion and readline
should be more consistent.
40. When the read builtin times out, it attempts to assign any input read to
specified variables, which also causes variables to be set to the empty
string if there is not enough input. Previous versions discarded the
characters read.
41. Beginning with bash-4.0, when one of the commands in a pipeline is killed
by a SIGINT while executing a command list, the shell acts as if it
received the interrupt. This can be disabled by setting the compat31 or
compat32 shell options.
42. Bash-4.0 changes the handling of the set -e option so that the shell exits
if a pipeline fails (and not just if the last command in the failing
pipeline is a simple command). This is not as Posix specifies. There is
work underway to update this portion of the standard; the bash-4.0
behavior attempts to capture the consensus at the time of release.
43. Bash-4.0 fixes a Posix mode bug that caused the . (source) builtin to
search the current directory for its filename argument, even if "." is
not in $PATH. Posix says that the shell shouldn't look in $PWD in this
case.
44. Bash-4.1 uses the current locale when comparing strings using the < and
> operators to the `[[' command. This can be reverted to the previous
behavior (ASCII collating and strcmp(3)) by setting one of the
`compatNN' shopt options, where NN is less than 41.
45. Bash-4.1 conforms to the current Posix specification for `set -u':
expansions of $@ and $* when there are no positional parameters do not
cause the shell to exit.
46. Bash-4.1 implements the current Posix specification for `set -e' and
exits when any command fails, not just a simple command or pipeline.
47. Command substitutions now remove the caller's trap strings when trap is
run to set a new trap in the subshell. Previous to bash-4.2, the old
trap strings persisted even though the actual signal handlers were reset.
48. When in Posix mode, a single quote is not treated specially in a
double-quoted ${...} expansion, unless the expansion operator is
# or % or the new `//', `^', or `,' expansions. In particular, it
does not define a new quoting context. This is from Posix interpretation
221.
49. Posix mode shells no longer exit if a variable assignment error occurs
with an assignment preceding a command that is not a special builtin.
50. Bash-4.2 attempts to preserve what the user typed when performing word
completion, instead of, for instance, expanding shell variable
references to their value.
51. When in Posix mode, bash-4.2 exits if the filename supplied as an argument
to `.' is not found and the shell is not interactive.
52. When compiled for strict Posix compatibility, bash-4.3 does not enable
history expansion by default in interactive shells, since it results in
a non-conforming environment.
53. Bash-4.3 runs the replacement string in the pattern substitution word
expansion through quote removal. The code already treats quote
characters in the replacement string as special; if it treats them as
special, then quote removal should remove them.
Shell Compatibility Level
=========================
Bash-4.0 introduced the concept of a `shell compatibility level', specified
as a set of options to the shopt builtin (compat31, compat32, compat40,
compat41, and compat42 at this writing). There is only one current
compatibility level -- each option is mutually exclusive. This list does not
mention behavior that is standard for a particular version (e.g., setting
compat32 means that quoting the rhs of the regexp matching operator quotes
special regexp characters in the word, which is default behavior in bash-3.2
and above).
Bash-4.3 introduces a new shell variable: BASH_COMPAT. The value assigned
to this variable (a decimal version number like 4.2, or an integer
corresponding to the compatNN option, like 42) determines the compatibility
level.
compat31 set
- the < and > operators to the [[ command do not consider the current
locale when comparing strings; they use ASCII ordering
- quoting the rhs of the regexp matching operator (=~) has no
special effect
compat32 set
- the < and > operators to the [[ command do not consider the current
locale when comparing strings; they use ASCII ordering
compat40 set
- the < and > operators to the [[ command do not consider the current
locale when comparing strings; they use ASCII ordering
- interrupting a command list such as "a ; b ; c" causes the execution
of the entire list to be aborted (in versions before bash-4.0,
interrupting one command in a list caused the next to be executed)
compat41 set
- interrupting a command list such as "a ; b ; c" causes the execution
of the entire list to be aborted (in versions before bash-4.1,
interrupting one command in a list caused the next to be executed)
- when in posix mode, single quotes in the `word' portion of a
double-quoted parameter expansion define a new quoting context and
are treated specially
compat42 set
- the replacement string in double-quoted pattern substitution is not
run through quote removal, as in previous versions
-------------------------------------------------------------------------------
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved. This file is offered as-is,
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0707010007eb38000081a40000000000000000000000015428b735000006a900000100000100b5ffffffffffffffff0000002400000000root/usr/local/share/doc/bash/RBASH 6.10 The Restricted Shell
=========================
If Bash is started with the name `rbash', or the `--restricted' or `-r'
option is supplied at invocation, the shell becomes restricted. A
restricted shell is used to set up an environment more controlled than
the standard shell. A restricted shell behaves identically to `bash'
with the exception that the following are disallowed or not performed:
* Changing directories with the `cd' builtin.
* Setting or unsetting the values of the `SHELL', `PATH', `ENV', or
`BASH_ENV' variables.
* Specifying command names containing slashes.
* Specifying a filename containing a slash as an argument to the `.'
builtin command.
* Specifying a filename containing a slash as an argument to the `-p'
option to the `hash' builtin command.
* Importing function definitions from the shell environment at
startup.
* Parsing the value of `SHELLOPTS' from the shell environment at
startup.
* Redirecting output using the `>', `>|', `<>', `>&', `&>', and `>>'
redirection operators.
* Using the `exec' builtin to replace the shell with another command.
* Adding or deleting builtin commands with the `-f' and `-d' options
to the `enable' builtin.
* Using the `enable' builtin command to enable disabled shell
builtins.
* Specifying the `-p' option to the `command' builtin.
* Turning off restricted mode with `set +r' or `set +o restricted'.
These restrictions are enforced after any startup files are read.
When a command that is found to be a shell script is executed (*note
Shell Scripts::), `rbash' turns off any restrictions in the shell
spawned to execute the script.
0707010007eb3f000041ed0000000000000000000000265428b7c80000000000000100000100b5ffffffffffffffff0000001c00000000root/usr/local/share/locale 0707010007eba0000041ed0000000000000000000000035428b7c80000000000000100000100b5ffffffffffffffff0000001f00000000root/usr/local/share/locale/uk 0707010007eba1000041ed0000000000000000000000025428b7c80000000000000100000100b5ffffffffffffffff0000002b00000000root/usr/local/share/locale/uk/LC_MESSAGES 0707010007eba2000081a40000000000000000000000015428b738000365df00000100000100b5ffffffffffffffff0000003300000000root/usr/local/share/locale/uk/LC_MESSAGES/bash.mo 0 # . * . / <