Pod::Usage - extracts POD documentation and shows usage information

      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 => $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 );

    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

    *   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" *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" 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" *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.


        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.:


        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.:


        will print any "=head2 Caveats" section (only) within any of the
        three "=head1" sections.

        Alternatively, an array reference of section specifications can be

          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

    "-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

        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).

        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.

        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" *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. This 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

    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

    Unless they are explicitly specified, the default values for the exit
    status, verbose level, and output stream to use are determined as

    *   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

    *   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 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 pod2usage() to accept a single number or a string makes it
    convenient to use as an innocent looking error message handling

        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".

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

    Each of the following invocations of "pod2usage()" will print just the
    "SYNOPSIS" section to "STDERR" and will exit with a status of 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(-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

        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));


        =head1 NAME

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

        =head1 SYNOPSIS

        sample [options] [file ...]

           -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.


        =head1 DESCRIPTION

        B<This program> will read the given input file(s) and do something
        useful with the contents thereof.


    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 is not 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

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

    This module is managed in a GitHub repository,
    <> Feel free to fork and
    contribute, or to clone and send patches!

    Please use <> to file a
    bug report. The previous ticketing system,
    <>, is deprecated
    for this package.

    More general questions or discussion about POD should be sent to the
    "" mail list. Send an empty email to
    "" to subscribe.

    Marek Rouchal <>

    Nicolas R <>

    Brad Appleton <>

    Based on code for Pod::Text::pod2text() written by Tom Christiansen

    Pod::Usage (the distribution) is licensed under the same terms as Perl.

    Nicolas R (ATOOMIC) for setting up the Github repo and modernizing this

    rjbs for refactoring Pod::Usage to not use Pod::Parser any more.

    Steven McDougall <> for his help and patience with
    re-writing this manpage.

    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