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Pod::Usage(3)	       Perl Programmers	Reference Guide		 Pod::Usage(3)

NAME
       Pod::Usage - print a usage message from embedded	pod documentation

SYNOPSIS
	 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 );

ARGUMENTS
       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:

       o   A string containing the text	of a message to	print before printing
	   the usage message

       o   A numeric value corresponding to the	desired	exit status

       o   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" string
       "-msg" string
	   The text of a message to print immediately prior to printing	the
	   program's usage message.

       "-exitval" value
	   The desired exit status to pass to the exit() 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" value
	   The desired level of	"verboseness" to use when printing the usage
	   message.  If	the value is 0,	then only the "SYNOPSIS" section of
	   the pod documentation is printed. If	the 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, 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" spec
	   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|ENVIORNMENT/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" handle
	   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"	handle
	   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
	   English.pm).

	   If you are calling pod2usage() 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" string
	   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. The -noperldoc 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,	the
	   -perlcmd option may be used to supply the path to a perl executable
	   which should	run perldoc.

       "-perldoc" path-to-perldoc
	   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" string
	   By default, Pod::Usage will call perldoc when -verbose >= 2 is
	   specified.  The -perldocopt option may be used to supply options to
	   perldoc. The	string may contain several, space-separated options.

   Formatting base class
       The default text	formatter is Pod::Text.	The base class for Pod::Usage
       can be defined by pre-setting $Pod::Usage::Formatter before loading
       Pod::Usage, e.g.:

	   BEGIN { $Pod::Usage::Formatter = 'Pod::Text::Termcap'; }
	   use Pod::Usage qw(pod2usage);

       Pod::Usage uses Pod::Simple's _handle_element_end() 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.

   Pass-through	options
       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

DESCRIPTION
       pod2usage 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:

       o   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.

       o   If an exit status is	specified but the verbose level	is not,	then
	   the verbose level will default to 1 if the exit status is less than
	   2 and will default to 0 otherwise.

       o   If an exit status is	not specified but verbose level	is given, then
	   the exit status will	default	to 2 if	the verbose level is 0 and
	   will	default	to 1 otherwise.

       o   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:

       o   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.

       o   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 did not find a	matching line for the given regular
	   expression.

       o   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.

       o   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 -help on the	command	line)
	   should go to	"STDOUT", just in case the user	wants to pipe the
	   output to a pager (such as more(1)).

       o   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 of pod2usage() 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, there's more	than one way to	do it, and
       pod2usage() adheres to this philosophy.	If you are interested in
       seeing a	number of different ways to invoke pod2usage (although by no
       means exhaustive), please refer to "EXAMPLES".

   Scripts
       The Pod::Usage distribution comes with a	script pod2usage which offers
       a command line interface	to the functionality of	Pod::Usage. See
       pod2usage.

EXAMPLES
       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});

   Recommended Use
       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 Pod::Usage in combination with Getopt::Long	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

CAVEATS
       By 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 path
       and 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 use FindBin to locate the
       script:

	   use FindBin;
	   pod2usage(-input => $FindBin::Bin . "/" . $FindBin::Script);

AUTHOR
       Please report bugs using	<http://rt.cpan.org>.

       Marek Rouchal <marekr@cpan.org>

       Brad Appleton <bradapp@enteract.com>

       Based on	code for Pod::Text::pod2text() written by Tom Christiansen
       <tchrist@mox.perl.com>

ACKNOWLEDGMENTS
       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.

SEE ALSO
       Pod::Usage 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 v5.26.0			  2017-04-19			 Pod::Usage(3)

NAME | SYNOPSIS | ARGUMENTS | DESCRIPTION | EXAMPLES | CAVEATS | AUTHOR | ACKNOWLEDGMENTS | SEE ALSO

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