Pod::Usage(3p) Perl Programmers Reference Guide Pod::Usage(3p) #
Pod::Usage(3p) Perl Programmers Reference Guide Pod::Usage(3p)
NNAAMMEE #
Pod::Usage - extracts POD documentation and shows usage information
SSYYNNOOPPSSIISS #
use Pod::Usage;
my $message_text = "This text precedes the usage message.";
my $exit_status = 2; ## The exit status to use
my $verbose_level = 0; ## The verbose level to use
my $filehandle = \*STDERR; ## The filehandle to write to
pod2usage($message_text);
pod2usage($exit_status);
pod2usage( { -message => $message_text ,
-exitval => $exit_status ,
-verbose => $verbose_level,
-output => $filehandle } );
pod2usage( -msg => $message_text ,
-exitval => $exit_status ,
-verbose => $verbose_level,
-output => $filehandle );
pod2usage( -verbose => 2,
-noperldoc => 1 );
pod2usage( -verbose => 2,
-perlcmd => $path_to_perl,
-perldoc => $path_to_perldoc,
-perldocopt => $perldoc_options );
AARRGGUUMMEENNTTSS #
ppoodd22uussaaggee should be given either a single argument, or a list of
arguments corresponding to an associative array (a "hash"). When a single
argument is given, it should correspond to exactly one of the following:
• A string containing the text of a message to print _b_e_f_o_r_e printing
the usage message
• A numeric value corresponding to the desired exit status
• A reference to a hash
If more than one argument is given then the entire argument list is
assumed to be a hash. If a hash is supplied (either as a reference or as
a list) it should contain one or more elements with the following keys:
"-message" _s_t_r_i_n_g
"-msg" _s_t_r_i_n_g
The text of a message to print immediately prior to printing the
program's usage message.
"-exitval" _v_a_l_u_e
The desired exit status to pass to the eexxiitt(()) function. This should
be an integer, or else the string "NOEXIT" to indicate that control
should simply be returned without terminating the invoking process.
"-verbose" _v_a_l_u_e
The desired level of "verboseness" to use when printing the usage
message. If the value is 0, then only the "SYNOPSIS" and/or "USAGE"
sections of the pod documentation are printed. If the value is 1,
then the "SYNOPSIS" and/or "USAGE" sections, along with any section
entitled "OPTIONS", "ARGUMENTS", or "OPTIONS AND ARGUMENTS" is
printed. If the corresponding value is 2 or more then the entire
manpage is printed, using perldoc if available; otherwise Pod::Text
is used for the formatting. For better readability, the all-capital
headings are downcased, e.g. "SYNOPSIS" => "Synopsis".
The special verbosity level 99 requires to also specify the -sections
parameter; then these sections are extracted and printed.
"-sections" _s_p_e_c
There are two ways to specify the selection. Either a string (scalar)
representing a selection regexp for sections to be printed when
-verbose is set to 99, e.g.
“NAME|SYNOPSIS|DESCRIPTION|VERSION” #
With the above regexp all content following (and including) any of
the given "=head1" headings will be shown. It is possible to restrict
the output to particular subsections only, e.g.:
"DESCRIPTION/Algorithm"
This will output only the "=head2 Algorithm" heading and content
within the "=head1 DESCRIPTION" section. The regexp binding is
stronger than the section separator, such that e.g.:
"DESCRIPTION|OPTIONS|ENVIRONMENT/Caveats"
will print any "=head2 Caveats" section (only) within any of the
three "=head1" sections.
Alternatively, an array reference of section specifications can be
used:
pod2usage(-verbose => 99, -sections => [
qw(DESCRIPTION DESCRIPTION/Introduction) ] );
This will print only the content of "=head1 DESCRIPTION" and the
"=head2 Introduction" sections, but no other "=head2", and no other
"=head1" either.
"-output" _h_a_n_d_l_e
A reference to a filehandle, or the pathname of a file to which the
usage message should be written. The default is "\*STDERR" unless the
exit value is less than 2 (in which case the default is "\*STDOUT").
"-input" _h_a_n_d_l_e
A reference to a filehandle, or the pathname of a file from which the
invoking script's pod documentation should be read. It defaults to
the file indicated by $0 ($PROGRAM_NAME for users of _E_n_g_l_i_s_h_._p_m).
If you are calling ppoodd22uussaaggee(()) from a module and want to display that
module's POD, you can use this:
use Pod::Find qw(pod_where);
pod2usage( -input => pod_where({-inc => 1}, __PACKAGE__) );
"-pathlist" _s_t_r_i_n_g
A list of directory paths. If the input file does not exist, then it
will be searched for in the given directory list (in the order the
directories appear in the list). It defaults to the list of
directories implied by $ENV{PATH}. The list may be specified either
by a reference to an array, or by a string of directory paths which
use the same path separator as $ENV{PATH} on your system (e.g., ":"
for Unix, ";" for MSWin32 and DOS).
"-noperldoc"
By default, Pod::Usage will call perldoc when -verbose >= 2 is
specified. This does not work well e.g. if the script was packed
with PAR. This option suppresses the external call to perldoc and
uses the simple text formatter (Pod::Text) to output the POD.
"-perlcmd"
By default, Pod::Usage will call perldoc when -verbose >= 2 is
specified. In case of special or unusual Perl installations, this
option may be used to supply the path to a perl executable which
should run perldoc.
"-perldoc" _p_a_t_h_-_t_o_-_p_e_r_l_d_o_c
By default, Pod::Usage will call perldoc when -verbose >= 2 is
specified. In case perldoc is not installed where the perl
interpreter thinks it is (see Config), the -perldoc option may be
used to supply the correct path to perldoc.
"-perldocopt" _s_t_r_i_n_g
By default, Pod::Usage will call perldoc when -verbose >= 2 is
specified. This option may be used to supply options to perldoc. The
string may contain several, space-separated options.
FFoorrmmaattttiinngg bbaassee ccllaassss The default text formatter is Pod::Text. The base class for Pod::Usage can be defined by pre-setting $Pod::Usage::Formatter _b_e_f_o_r_e loading Pod::Usage, e.g.:
BEGIN { $Pod::Usage::Formatter = 'Pod::Text::Termcap'; }
use Pod::Usage qw(pod2usage);
Pod::Usage uses Pod::Simple's __hhaannddllee__eelleemmeenntt__eenndd(()) method to implement
the section selection, and in case of verbosity < 2 it down-cases the
all-caps headings to first capital letter and rest lowercase, and adds a
colon/newline at the end of the headings, for better readability. Same
for verbosity = 99.
PPaassss--tthhrroouugghh ooppttiioonnss The following options are passed through to the underlying text formatter. See the manual pages of these modules for more information.
alt code indent loose margin quotes sentence stderr utf8 width
DDEESSCCRRIIPPTTIIOONN #
ppoodd22uussaaggee will print a usage message for the invoking script (using its
embedded pod documentation) and then exit the script with the desired
exit status. The usage message printed may have any one of three levels
of "verboseness": If the verbose level is 0, then only a synopsis is
printed. If the verbose level is 1, then the synopsis is printed along
with a description (if present) of the command line options and
arguments. If the verbose level is 2, then the entire manual page is
printed.
Unless they are explicitly specified, the default values for the exit
status, verbose level, and output stream to use are determined as
follows:
• If neither the exit status nor the verbose level is specified, then
the default is to use an exit status of 2 with a verbose level of 0.
• If an exit status _i_s specified but the verbose level is _n_o_t, then the
verbose level will default to 1 if the exit status is less than 2 and
will default to 0 otherwise.
• If an exit status is _n_o_t specified but verbose level _i_s given, then
the exit status will default to 2 if the verbose level is 0 and will
default to 1 otherwise.
• If the exit status used is less than 2, then output is printed on
"STDOUT". Otherwise output is printed on "STDERR".
Although the above may seem a bit confusing at first, it generally does
"the right thing" in most situations. This determination of the default
values to use is based upon the following typical Unix conventions:
• An exit status of 0 implies "success". For example, ddiiffff((11)) exits
with a status of 0 if the two files have the same contents.
• An exit status of 1 implies possibly abnormal, but non-defective,
program termination. For example, ggrreepp((11)) exits with a status of 1
if it did _n_o_t find a matching line for the given regular expression.
• An exit status of 2 or more implies a fatal error. For example, llss((11))
exits with a status of 2 if you specify an illegal (unknown) option
on the command line.
• Usage messages issued as a result of bad command-line syntax should
go to "STDERR". However, usage messages issued due to an explicit
request to print usage (like specifying --hheellpp on the command line)
should go to "STDOUT", just in case the user wants to pipe the output
to a pager (such as mmoorree((11))).
• If program usage has been explicitly requested by the user, it is
often desirable to exit with a status of 1 (as opposed to 0) after
issuing the user-requested usage message. It is also desirable to
give a more verbose description of program usage in this case.
ppoodd22uussaaggee does not force the above conventions upon you, but it will use
them by default if you don't expressly tell it to do otherwise. The
ability of ppoodd22uussaaggee(()) to accept a single number or a string makes it
convenient to use as an innocent looking error message handling function:
use strict;
use Pod::Usage;
use Getopt::Long;
## Parse options
my %opt;
GetOptions(\%opt, "help|?", "man", "flag1") || pod2usage(2);
pod2usage(1) if ($opt{help});
pod2usage(-exitval => 0, -verbose => 2) if ($opt{man});
## Check for too many filenames
pod2usage("$0: Too many files given.\n") if (@ARGV > 1);
Some user's however may feel that the above "economy of expression" is
not particularly readable nor consistent and may instead choose to do
something more like the following:
use strict;
use Pod::Usage qw(pod2usage);
use Getopt::Long qw(GetOptions);
## Parse options
my %opt;
GetOptions(\%opt, "help|?", "man", "flag1") ||
pod2usage(-verbose => 0);
pod2usage(-verbose => 1) if ($opt{help});
pod2usage(-verbose => 2) if ($opt{man});
## Check for too many filenames
pod2usage(-verbose => 2, -message => "$0: Too many files given.\n")
if (@ARGV > 1);
As with all things in Perl, _t_h_e_r_e_'_s _m_o_r_e _t_h_a_n _o_n_e _w_a_y _t_o _d_o _i_t, and
ppoodd22uussaaggee(()) adheres to this philosophy. If you are interested in seeing
a number of different ways to invoke ppoodd22uussaaggee (although by no means
exhaustive), please refer to "EXAMPLES".
SSccrriippttss The Pod::Usage distribution comes with a script pod2usage which offers a command line interface to the functionality of Pod::Usage. See pod2usage.
EEXXAAMMPPLLEESS #
Each of the following invocations of "pod2usage()" will print just the
"SYNOPSIS" section to "STDERR" and will exit with a status of 2:
pod2usage();
pod2usage(2);
pod2usage(-verbose => 0);
pod2usage(-exitval => 2);
pod2usage({-exitval => 2, -output => \*STDERR});
pod2usage({-verbose => 0, -output => \*STDERR});
pod2usage(-exitval => 2, -verbose => 0);
pod2usage(-exitval => 2, -verbose => 0, -output => \*STDERR);
Each of the following invocations of "pod2usage()" will print a message
of "Syntax error." (followed by a newline) to "STDERR", immediately
followed by just the "SYNOPSIS" section (also printed to "STDERR") and
will exit with a status of 2:
pod2usage("Syntax error.");
pod2usage(-message => "Syntax error.", -verbose => 0);
pod2usage(-msg => "Syntax error.", -exitval => 2);
pod2usage({-msg => "Syntax error.", -exitval => 2, -output => \*STDERR});
pod2usage({-msg => "Syntax error.", -verbose => 0, -output => \*STDERR});
pod2usage(-msg => "Syntax error.", -exitval => 2, -verbose => 0);
pod2usage(-message => "Syntax error.",
-exitval => 2,
-verbose => 0,
-output => \*STDERR);
Each of the following invocations of "pod2usage()" will print the
"SYNOPSIS" section and any "OPTIONS" and/or "ARGUMENTS" sections to
"STDOUT" and will exit with a status of 1:
pod2usage(1);
pod2usage(-verbose => 1);
pod2usage(-exitval => 1);
pod2usage({-exitval => 1, -output => \*STDOUT});
pod2usage({-verbose => 1, -output => \*STDOUT});
pod2usage(-exitval => 1, -verbose => 1);
pod2usage(-exitval => 1, -verbose => 1, -output => \*STDOUT});
Each of the following invocations of "pod2usage()" will print the entire
manual page to "STDOUT" and will exit with a status of 1:
pod2usage(-verbose => 2);
pod2usage({-verbose => 2, -output => \*STDOUT});
pod2usage(-exitval => 1, -verbose => 2);
pod2usage({-exitval => 1, -verbose => 2, -output => \*STDOUT});
RReeccoommmmeennddeedd UUssee Most scripts should print some type of usage message to “STDERR” when a command line syntax error is detected. They should also provide an option (usually “-H” or “-help”) to print a (possibly more verbose) usage message to “STDOUT”. Some scripts may even wish to go so far as to provide a means of printing their complete documentation to “STDOUT” (perhaps by allowing a “-man” option). The following complete example uses PPoodd::::UUssaaggee in combination with GGeettoopptt::::LLoonngg to do all of these things:
use strict;
use Getopt::Long qw(GetOptions);
use Pod::Usage qw(pod2usage);
my $man = 0;
my $help = 0;
## Parse options and print usage if there is a syntax error,
## or if usage was explicitly requested.
GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
pod2usage(1) if $help;
pod2usage(-verbose => 2) if $man;
## If no arguments were given, then allow STDIN to be used only
## if it's not connected to a terminal (otherwise print usage)
pod2usage("$0: No files given.") if ((@ARGV == 0) && (-t STDIN));
END #
=head1 NAME
sample - Using GetOpt::Long and Pod::Usage
=head1 SYNOPSIS
sample [options] [file ...]
Options:
-help brief help message
-man full documentation
=head1 OPTIONS
=over 4
=item B<-help>
Print a brief help message and exits.
=item B<-man>
Prints the manual page and exits.
=back
=head1 DESCRIPTION
B<This program> will read the given input file(s) and do something
useful with the contents thereof.
=cut
CCAAVVEEAATTSS #
By default, ppoodd22uussaaggee(()) will use $0 as the path to the pod input file.
Unfortunately, not all systems on which Perl runs will set $0 properly
(although if $0 is not found, ppoodd22uussaaggee(()) will search $ENV{PATH} or else
the list specified by the "-pathlist" option). If this is the case for
your system, you may need to explicitly specify the path to the pod docs
for the invoking script using something similar to the following:
pod2usage(-exitval => 2, -input => "/path/to/your/pod/docs");
In the pathological case that a script is called via a relative path _a_n_d
the script itself changes the current working directory (see "chdir" in
perlfunc) _b_e_f_o_r_e calling pod2usage, Pod::Usage will fail even on robust
platforms. Don't do that. Or use FindBin to locate the script:
use FindBin;
pod2usage(-input => $FindBin::Bin . "/" . $FindBin::Script);
SSUUPPPPOORRTT #
This module is managed in a GitHub repository,
<https://github.com/Dual-Life/Pod-Usage> Feel free to fork and
contribute, or to clone and send patches!
Please use <https://github.com/Dual-Life/Pod-Usage/issues/new> to file a
bug report. The previous ticketing system,
<https://rt.cpan.org/Dist/Display.html?Queue=Pod-Usage>, is deprecated
for this package.
More general questions or discussion about POD should be sent to the
"pod-people@perl.org" mail list. Send an empty email to
"pod-people-subscribe@perl.org" to subscribe.
AAUUTTHHOORR #
Marek Rouchal <marekr@cpan.org>
Nicolas R <nicolas@atoomic.org>
Brad Appleton <bradapp@enteract.com>
Based on code for PPoodd::::TTeexxtt::::ppoodd22tteexxtt(()) written by Tom Christiansen
<tchrist@mox.perl.com>
LLIICCEENNSSEE #
Pod::Usage (the distribution) is licensed under the same terms as Perl.
AACCKKNNOOWWLLEEDDGGMMEENNTTSS #
Nicolas R (ATOOMIC) for setting up the Github repo and modernizing this
package.
rjbs for refactoring Pod::Usage to not use Pod::Parser any more.
Steven McDougall <swmcd@world.std.com> for his help and patience with re-
writing this manpage.
SSEEEE AALLSSOO #
PPoodd::::UUssaaggee is now a standalone distribution, depending on Pod::Text which
in turn depends on Pod::Simple.
Pod::Perldoc, Getopt::Long, Pod::Find, FindBin, Pod::Text,
Pod::Text::Termcap, Pod::Simple
perl v5.36.3 2023-02-15 Pod::Usage(3p)