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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:

       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"
       "-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:

       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 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 v5.12.1                      2010-04-26                   Pod::Usage(3pm)
 

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Gedruckt am: 24.08.2017 12:43 GMT+0200 (2017-08-24T12:43:53+02:00)