Provided by: perl-doc_5.18.2-2ubuntu1.7_all 
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.
Formatting base class
The default text formatter depends on the Perl version (Pod::Text or Pod::PlainText for Perl versions <
5.005_58). 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);
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:
• 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. 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
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.
Pod::Parser, Pod::Perldoc, Getopt::Long, Pod::Find, FindBin, Pod::Text, Pod::PlainText,
Pod::Text::Termcap
perl v5.18.2 2014-01-06 Pod::Usage(3perl)