Data::ShowTable(3)
ShowTable - routines to display tabular data in several
formats.
USAGE
use Data::ShowTable;
ShowTable \@titles, \@types, \@widths, \&row_sub [,
\&fmt_sub ];
$Data::ShowTable::Show_Mode = 'mode';
$Data::ShowTable::Term_Columns = NNN;
$Data::ShowTable::Max_Table_Width = NNN;
$Data::ShowTable::No_Escape = flag;
%Data::ShowTable::URL_Keys = { "$colname" => "$col_URL",
... };
ShowRow $rewindflag, \$index, $col_array_1 [,
$col_array_2, ...;]
ShowDatabases \@dbnames;
ShowTables \@tblnames;
ShowColumns \@columns, \@col_types, \@col_lengths,
\@col_attrs;
ShowBoxTable \@titles, \@types, \@widths, \&row_sub [,
\&fmt_sub ];
ShowSimpleTable \@titles, \@types, \@widths, \&row_sub [,
\&fmt_sub];
ShowHTMLTable \@titles, \@types, \@widths, \&row_sub [,
\&fmt_sub];
ShowListTable \@titles, \@types, \@widths, \&row_sub [,
\&fmt_sub];
$fmt = ShowTableValue $value, $type, $max_width, $width,
$precision;
DESCRIPTION
The ShowTable module provides subroutines to display
tabular data, typially from a database, in nicely
formatted columns, in several formats. The output format
for any one invocation can be one of four possible styles:
Box A tabular format, with the column titles and the
ShowBoxTable for details.
Table A simple tabular format, with columns
automatically aligned, with column titles. See
the section on ShowSimpleTable.
List A list style, where columns of data are listed
as a name:value pair, one pair per line, with
rows being one or more column values, separated
by an empty line. See the section on
ShowListTable.
HTML The data is output as an HTML TABLE, suitable
for display through a Web-client. See the
section on ShowHTMLTable.
The subroutines which perform these displays are listed
below.
EXPORTED NAMES
This module exports the following subroutines:
ShowDatabases - show list of databases
ShowTables - show list of tables
ShowColumns - show table of column info
ShowTable - show a table of data
ShowRow - show a row from one or more columns
ShowTableValue - show a single column's value
ShowBoxTable - show a table of data in a box
ShowListTable - show a table of data in a list
ShowSimpleTable - show a table of data in a simple table
ShowHTMLTable - show a table of data using HTML
All of these subroutines, and others, are described in
detail in the following sections.
MODULES
ShowTable
Format and display the contents of one or more rows of
data.
ShowTable \@titles, \@types, \@widths, \&row_sub [,
\&fmt_sub ];
$Data::ShowTable::Show_Mode = 'mode';
$Data::ShowTable::Term_Columns = NNN;
$Data::ShowTable::Max_Table_Width = NNN;
$Data::ShowTable::No_Escape = flag;
display: Box, Table, List, and HTML. Each mode is
described separately below.
The arguments to ShowTable are:
\@titles A reference to an array of column names, or
titles. If a particular column name is null,
then the string Column num is used by default.
To have a column have no title, use the empty
string.
\@types A reference to an array of types, one for each
column. These types are passed to the fmt_sub
for appropriate formatting. Also, if a column
type matches the regexp "/text|char|string/i",
then the column alignment will be left-
justified, otherwise it will be right-justified.
\@widths A reference to an array of column widths, which
may be given as an integer, or as a string of
the form: "width.precision".
\&row_sub A reference to a subroutine which successively
returns rows of values in an array. It is
called for two purposes, each described
separately:
* To fetch successive rows of data:
@row = &$row_sub(0);
When given a null, zero, or empty argument, the
next row is returned.
* To initialize or rewind the data traversal.
$rewindable = &$row_sub(1);
When invoked with a non-null argument, the
subroutine should rewind its row pointer to
start at the first row of data. If the data
which row_sub is traversing is not rewindable,
it must return zero or null. If the data is
rewindable, a non-null, non-zero value should be
returned.
The row_sub must expect to be invoked once with
a non-null argument, in order to discover
whether or not the data is rewindable. If the
data cannot be rewound, row_sub will thereafter
only be called with a zero argument.
$rewindable = &$row_sub(1);
if ($rewindable) {
while ((@row = &$row_sub(0)), $#row >= 0) {
# examine lengths for optimal formatting
}
&$row_sub(1); # rewind
}
while ((@row = &$row_sub(0)), $#row >= 0) {
# format the data
}
The consequence of data that is not rewindable,
a reasonably nice table will still be formatted,
but it may contain fairly large amounts of
whitespace for wide columns.
\&fmt_sub A reference to a subroutine which formats a
value, according to its type, width, precision,
and the current column width. It is invoked
this way:
$string = &fmt_sub($value, $type, $max_width, $width, $precision)
The $max_width is the maximum width for the
column currently being formatted.
If $width is omitted, $max_width is assumed.
If $precision is omitted, zero is assumed.
If \&fmt_sub is omitted, then a default
subroutine, ShowTableValue, will be used, which
will use Perl's standard string formatting
rules.
ShowRow
Fetch rows successively from one or more columns of data.
ShowRow $rewindflag, \$index, $col_array_1 [,
$col_array_2, ...;]
The ShowRow subroutine returns a row of data from one or
more columns of data. It is designed to be used as a
callback routine, within the ShowTable routine. It can
be used to select elements from one or more array
reference arguments.
If passed two or more array references as arguments,
elements of the arrays selected by $index are returned as
the "row" of data.
the "row" of data.
If the $rewindflag flag is set, then the $index pointer is
reset to zero, and "true" is returned (a scalar 1). This
indicates that the data is rewindable to the ShowTable
routines.
When the $rewindflag is not set, then the current row of
data, as determined by $index is returned, and $index will
have been incremented.
An actual invocation (from ShowColumns) is:
ShowTable \@titles, \@types, \@lengths,
sub { &ShowRow( $_[0], \$current_row, $col_names, $col_types,
$col_lengths, \@col_attrs); };
In the example above, after each invocation, the
$current_row argument will have been incremented.
ShowDatabases
Show a list of database names.
ShowDatabases \@dbnames;
ShowDatabases is intended to be used to display a list of
database names, under the column heading of "Databases".
It is a special case usage of ShowTable.
The argument, \@dbnames, is a reference to an array of
strings.
ShowTables
Show an array of table names.
ShowTables \@tblnames;
ShowTables is used to display a list of table names, under
the column heading of "Tables". It is a special case
usage of ShowTable.
ShowColumns
Display a table of column names, types, and attributes.
ShowColumns \@columns, \@col_types, \@col_lengths,
\@col_attrs;
The ShowColumns subroutine displays a table of column
names, types, lengths, and other attributes in a nicely
formatted table. It is a special case usage of ShowTable.
The arguments are:
\@col_types
An array of column types names.
\@col_lengths
An array of maximum lengths for corresponding
columns.
\@col_attrs
An array of column attributes array references
(ie: an array of arrays). The attributes array
for the first column are at "$col_attrs-\>[0]".
The first attribute of the second column is
"$col_attrs-\>[1][0]".
The columns, types, lengths, and attributes are displayed
in a table with the column headings: "Column", "Type",
"Length", and "Attributes". This is a special case usage
of ShowTable.
ShowBoxTable
Show tabular data in a box.
ShowBoxTable \@titles, \@types, \@widths, \&row_sub [,
\&fmt_sub ];
The ShowBoxTable displays tabular data in titled columns
using a "box" of ASCII graphics, looking something like
this:
+------------+----------+-----+----------+
| Column1 | Column2 | ... | ColumnN |
+------------+----------+-----+----------+
| Value11 | Value12 | ... | Value 1M |
| Value21 | Value22 | ... | Value 2M |
| Value31 | Value32 | ... | Value 3M |
| ... | ... | ... | ... |
| ValueN1 | ValueN2 | ... | Value NM |
+------------+----------+-----+----------+
The arguments are the same as with ShowTable. If the
@titles array is empty, the header row is omitted.
ShowSimpleTable
Display a table of data using a simple table format.
ShowSimpleTable \@titles, \@types, \@widths, \&row_sub
[, \&fmt_sub];
The ShowSimpleTable subroutine formats data into a simple
table of aligned columns, in the following example:
------- ------- -------
Value1 Value2 Value3
Value12 Value22 Value32
Columns are auto-sized by the data's widths, plus two
spaces between columns. Values which are too long for the
maximum colulmn width are wrapped within the column.
ShowHTMLTable
Display a table of data nicely using HTML tables.
ShowHTMLTable \@titles, \@types, \@widths, \&row_sub [,
\&fmt_sub];
The ShowHTMLTable displays one or more rows of columns of
data using the HTML C<\ShowTable.
If the @titles array is empty, no header row is generated.
There is a variable which controls if and how hypertext
links are generated within the table:
%URL_Keys This is a hash array of column names (titles)
and corresponding base URLs. The values of any
columns occuring as keys in the hash array will
be generated as hypertext anchors using the
associated base URL and the column name and
value as a querystring for the "col" and "val"
parameters, respectively.
For example, if we define the array:
$base_url = "http://www.$domain/cgi/lookup";
%url_cols = ('Author' => $base_url,
'Name' => $base_url);
Then, the values in the Author column will be generated
with the following HTML text:
<A HREF="http://www.$domain/cgi/lookup?col=Author?val=somevalue>somevalue</A>
and the values in the Name column will be generated with
the URL:
<A HREF="http://www.$domain/cgi/lookup?col=Name?val=othervalue>othervalue</A>
ShowListTable
Display a table of data using a list format.
ShowListTable \@titles, \@types, \@widths, \&row_sub [,
displayed wth a field name and value pair per line, with
records being one or more fields . In other words, the
output of a table would look something like this:
Field1-1: Value1-1
Field1-2: Value1-2
Field1-3: Value1-3
...
Field1-N: Value1-M
<empty line>
Field2-1: Value2-1
Field2-2: Value2-2
Field2-3: Value2-3
...
Field2-N: Value2-N
...
FieldM-1: ValueM-1
FieldM-2: ValueM-2
...
FieldM-N: ValueM-N
<empty line>
<empty line>
Characteristics of List mode:
o two empty lines indicate the end of data.
o An empty field (column) may be omitted, or may
have a label, but no data.
o A long line can be continue by a null field
(column):
Field2: blah blah blah
: blah blah blah
o On a continuation, the null field is an
arbitrary number of leading white space, a colon
':', a single blank or tab, followed by the
continued text.
o Embedded newlines are indicated by the escape
mechanism "\n". Similarly, embedded tabs are
indicated with "\t", returns with "\r".
o If the @Titles array is empty, the field names
"Field NN" are used instead.
ShowTableValue
Prepare and return a formatted representation of a value.
A value argument, using its corresponding type, effective
$fmt = ShowTableValue $value, $type, $max_width, $width,
$precision;
$value The value to be formatted.
$type The type name of the value; eg: char, varchar,
int, etc.
$max_width
The maximum width of any value in the current
value's column. If $width is zero or null,
$max_width is used by default. $max_width is
also used as a minimum width, in case $width is
a smaller value.
$width The default width of the value, obtained from
the width specification of the column in which
this value occurs.
$precision
The precision specification, if any, from the
column width specification.
VARIABLES
The following variables may be set by the user to affect
the display (with the defaults enclosed in square brackets
[..]):
$Show_Mode [Box]
This is the default display mode when using
ShowTable. The environment variable,
$ENV{'SHOWMODE'}, is used when this variable is
null or the empty string. The possible values
for this variable are: "Box", "List", "Table",
and "HTML". Case is insignificant.
$List_Wrap_Margin [2]
This variable's value determines how large a
margin to keep before wrarpping a long value's
display in a column. This value is only used in
"List" mode.
$Term_Columns [80]
This variable, used in "List" mode, is used to
determine how long an output line may be before
wrapping it. The environment variable,
$ENV{'COLUMNS'}, is used to define this value
when it is null.
$Max_Table_Width ['']
This variable, when set, causes all tables to
this variable is not set, which is the default
case, there is no maximum table width, and no
scaling will be done.
$No_Escape ['']
If set, allows embedded HTML text to be included
in the data displayed in an HTML-formatted
table. By default, the HTML formatting
characters ("<", ">", and "&") occuring in
values are escaped.
%URL_Keys In HTML mode, this variable is used to recognize
which columns are to be displayed with a
corresponding hypertext anchor. See the section
on ShowHTMLTable for more details.
INTERNAL SUBROUTINES
calc_widths
($num_cols, $widths, $precision, $max_widths) =
&calc_widths( $widthspec, $titles, $rewindable,
$row_sub, $fmt_sub, $types, $showmode);
DESCRIPTION
calc_widths is a generalized subroutine used by all the
ShowTable variant subroutines to setup internal variables
prior to formatting for display. Calc_widths handles the
column width and precision analysis, including scanning
the data (if rewindable) for appropriate default values.
The number of columns in the data is returned, as well as
three arrays: the declared column widths, the column
precision values, and the maximum column widths.
RETURN VALUES
$num_cols is the number of columns in the data. If the
data is not rewindable, this is computed as the
maximum of the number of elements in the
$widthspec array and the number of elements in
the $titles array. When the data is rewindable,
this is the maximum of the number of columns of
each row of data.
$widths is the column widths array ref, without the
precision specs (if any). Each column's width
value is determined by the original $widthspec
value and/or the maximum length of the formatted
data for the column.
$precision
original precision component from the
$widthspec, and the data is rewindable, then the
data is examined to determine the maximum
default precision.
$max_widths
is the ref to the array of maximum widths for
the given columns.
ARGUMENTS
$widthspec
A reference to an array of column width (or
length) values, each given as an integer, real
number, or a string value of "width.precision".
If a value is zero or null, the length of the
corresponding formatted data (if rewindable) and
column title length are used to determine a
reasonable default.
If a column's width portion is a positive, non-
zero number, then the column will be this wide,
regardless of the values lengths of the data in
the column.
If the column's width portion is given as a
negative number, then the positive value is used
as a minimum column width, with no limit on the
maximum column width. In other words, the
column will be at least width characters wide.
If the data is not rewindable, and a column's
width value is null or zero, then the length of
the column title is used. This may cause severe
wrapping of data in the column, if the column
data lengths are much greater than the column
title widths.
$titles The array ref to the column titles; used to
determine the minimum acceptable width, as well
as the default number of columns. If the
$titles array is empty, then the $widthspec
array is used to determine the default number of
columns.
$rewindable
A flag indicating whether or not the data being
formatted is rewindable. If this is true, a
pass over the data will be done in order to
calculate the maximum lengths of the actual
formatted data, using $fmt_sub (below), rather
(ie: the actual column widths may be less than
the declared column widths).
If it is not desired to have the column widths
dynamically adjusted, then set the $rewindable
argument to 0, even if the data is rewindable.
$row_sub The code reference to the subroutine which
returns the data; invoked only if $rewindable is
non-null.
$fmt_sub The subroutine used to determine the length of
the data when formatted; if this is omitted or
null, the length of the data is used by default.
The $fmt_sub is used only when the data is
rewindable.
$types An array reference to the types of each of the
value columns; used only when $fmt_sub is
invoked.
$showmode A string indicating the mode of the eventual
display; one of four strings: "box", "table",
"list", and "html". Used to adjust widths for
formatting requirements.
putcell
$wrapped = &putcell( \@cells, $c, $cell_width, \@prefix,
\@suffix, $wrap_flag );
Output the contents of an array cell at $cell[$c], causing
text longer than $cell_width to be saved for output on
subsequent calls. Prefixing the output of each cell's
value is a string from the two-element array @prefix.
Suffixing each cell's value is a string from the two-
element array @suffix. The first element of either array
is selected when $wrap_flag is zero or null, or when there
is no more text in the current to be output. The second
element is selected when $wrap_flag is non-zero, and when
there is more text in the current cell to be output.
In the case of text longer than $cell_width, a non-zero
value is returned.
Cells with undefined data are not output, nor are the
prefix or suffix strings.
center
Center a string within a given width.
$field = center $string, $width;
Compute the maximum value from a list of values.
$max = &max( @values );
min
Compute the minum value from a list of values.
$min = &min( @values );
max_length
Compute the maximum length of a set of strings in an array
reference.
$maxlength = &max_length( \@array_ref );
htmltext
Translate regular text for output into an HTML document.
This means certain characters, such as "&", ">", and "<"
must be escaped.
$output = &htmltext( $input );
AUTHOR
Alan K. Stebbens <aks@sgi.com>