Pod::Usage, pod2usage() - print a usage message from embedded pod documentation
use Pod::Usagemy $message_text = "This text precedes the usage message.";my $exit_status = 2; ## The exit status to usemy $verbose_level = 0; ## The verbose level to usemy $filehandle = \*STDERR; ## The filehandle to write topod2usage($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 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 printbefore 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-msgThe text of a message to print immediately prior to printing the program's usage message.
-exitvalThe desired exit status to pass to theexit() function. This should be an integer, or else the string "NOEXIT" to indicate that control should simply be returned without terminating the invoking process.
-verboseThe desired level of "verboseness" to use when printing the usage message. If the corresponding value is 0, then only the "SYNOPSIS" section of the pod documentation is printed. If the corresponding value is 1, then the "SYNOPSIS" section, 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.
The special verbosity level 99 requires to also specify the -sections parameter; then these sections are extracted (seePod::Select) and printed.
-sectionsA string representing a selection list for sections to be printed when -verbose is set to 99, e.g."NAME|SYNOPSIS|DESCRIPTION|VERSION".
Alternatively, an array reference of section specifications can be used:
pod2usage(-verbose => 99, -sections => [ qw(fred fred/subsection) ] );-outputA 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).
-inputA 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 ofEnglish.pm).
If you are callingpod2usage() 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__) );-pathlistA 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).
-noperldocBy default, Pod::Usage will callperldoc when -verbose >= 2 is specified. This does not work well e.g. if the script was packed withPAR. The -noperldoc option suppresses the external call toperldoc and uses the simple text formatter (Pod::Text) to output the POD.
The default text formatter depends on the Perl version (Pod::Text orPod::PlainText for Perl versions < 5.005_58). The base class for Pod::Usage can be defined by pre-setting$Pod::Usage::Formatterbefore loading Pod::Usage, e.g.:
BEGIN { $Pod::Usage::Formatter = 'Pod::Text::Termcap'; }use Pod::Usage qw(pod2usage);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 widthpod2usage 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 statusis specified but the verbose level isnot, 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 isnot specified but verbose levelis 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 onSTDOUT. Otherwise output is printed onSTDERR.
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,diff(1) 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,grep(1) exits with a status of 1 if it didnot find a matching line for the given regular expression.
An exit status of 2 or more implies a fatal error. For example,ls(1) 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 toSTDERR. However, usage messages issued due to an explicit request to print usage (like specifying-help on the command line) should go toSTDOUT, just in case the user wants to pipe the output to a pager (such asmore(1)).
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.
pod2usage doesn't 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 ofpod2usage() to accept a single number or a string makes it convenient to use as an innocent looking error message handling function:
use Pod::Usage;use Getopt::Long;## Parse optionsGetOptions("help", "man", "flag1") || pod2usage(2);pod2usage(1) if ($opt_help);pod2usage(-verbose => 2) if ($opt_man);## Check for too many filenamespod2usage("$0: Too many files given.\n") if (@ARGV > 1);Some user's however may feel that the above "economy of expression" is not particularly readable nor consistent and may instead choose to do something more like the following:
use Pod::Usage;use Getopt::Long;## Parse optionsGetOptions("help", "man", "flag1") || pod2usage(-verbose => 0);pod2usage(-verbose => 1) if ($opt_help);pod2usage(-verbose => 2) if ($opt_man);## Check for too many filenamespod2usage(-verbose => 2, -message => "$0: Too many files given.\n") if (@ARGV > 1);As with all things in Perl,there's more than one way to do it, andpod2usage() adheres to this philosophy. If you are interested in seeing a number of different ways to invokepod2usage (although by no means exhaustive), please refer to"EXAMPLES".
Each of the following invocations ofpod2usage() will print just the "SYNOPSIS" section toSTDERR 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 ofpod2usage() will print a message of "Syntax error." (followed by a newline) toSTDERR, immediately followed by just the "SYNOPSIS" section (also printed toSTDERR) 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 ofpod2usage() will print the "SYNOPSIS" section and any "OPTIONS" and/or "ARGUMENTS" sections toSTDOUT 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 ofpod2usage() will print the entire manual page toSTDOUT 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});Most scripts should print some type of usage message toSTDERR 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 toSTDOUT. Some scripts may even wish to go so far as to provide a means of printing their complete documentation toSTDOUT (perhaps by allowing a-man option). The following complete example usesPod::Usage in combination withGetopt::Long to do all of these things:
use Getopt::Long;use Pod::Usage;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 NAMEsample - Using GetOpt::Long and Pod::Usage=head1 SYNOPSISsample [options] [file ...] Options: -help brief help message -man full documentation=head1 OPTIONS=over 8=item B<-help>Print a brief help message and exits.=item B<-man>Prints the manual page and exits.=back=head1 DESCRIPTIONB<This program> will read the given input file(s) and do somethinguseful with the contents thereof.=cutBy default,pod2usage() 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$0 isn't found,pod2usage() will search$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 pathand the script itself changes the current working directory (see"chdir" in perlfunc)before calling pod2usage, Pod::Usage will fail even on robust platforms. Don't do that. Or useFindBin to locate the script:
use FindBin;pod2usage(-input => $FindBin::Bin . "/" . $FindBin::Script);Please report bugs usinghttp://rt.cpan.org.
Marek Rouchal <marekr@cpan.org>
Brad Appleton <bradapp@enteract.com>
Based on code forPod::Text::pod2text() written by Tom Christiansen <tchrist@mox.perl.com>
Steven McDougall <swmcd@world.std.com> for his help and patience with re-writing this manpage.
Pod::Usage is now a standalone distribution.
Pod::Parser,Pod::Perldoc,Getopt::Long,Pod::Find,FindBin,Pod::Text,Pod::PlainText,Pod::Text::Termcap
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