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



NAME
       Pod::Usage, pod2usage() - 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  )

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:

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

       "-exitval"
           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"
           The 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 (see Pod::Select) and printed.

       "-sections"
           A 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) ] );

       "-output"
           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"
           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"
           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.

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:

       •   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 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.

       •   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.

       •   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, 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 did not 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 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)).

       •   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 Pod::Usage;
           use Getopt::Long;

           ## Parse options
           GetOptions("help", "man", "flag1")  ||  pod2usage(2);
           pod2usage(1)  if ($opt_help);
           pod2usage(-verbose => 2)  if ($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 Pod::Usage;
           use Getopt::Long;

           ## Parse options
           GetOptions("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".

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 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 NAME

           sample - Using GetOpt::Long and Pod::Usage

           =head1 SYNOPSIS

           sample [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 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.

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
       Steven McDougall <swmcd@world.std.com> for his help and patience with re-writing this manpage.

SEE ALSO
       Pod::Parser, Getopt::Long, Pod::Find



perl v5.12.5                                     2012-11-03                                  Pod::Usage(3pm)