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Manpages Pod::UsageSection: Perl Programmers Reference Guide (3perl)Updated: 2001-02-22 Index Return to Main Contents NAMEPod::Usage, pod2usage() - print a usage message from embedded pod documentationSYNOPSISuse 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 => $filehandle ); ARGUMENTSpod2usage should be given either a single argument, or a list of arguments corresponding to an associative array (a ``hash''). When a single argument is given, it should correspond to exactly one of the following:
If more than one argument is given then the entire argument list is assumed to be a hash. If a hash is supplied (either as a reference or as a list) it should contain one or more elements with the following keys:
DESCRIPTIONpod2usage will print a usage message for the invoking script (using its embedded pod documentation) and then exit the script with the desired exit status. The usage message printed may have any one of three levels of ``verboseness'': If the verbose level is 0, then only a synopsis is printed. If the verbose level is 1, then the synopsis is printed along with a description (if present) of the command line options and arguments. If the verbose level is 2, then the entire manual page is printed.Unless they are explicitly specified, the default values for the exit status, verbose level, and output stream to use are determined as follows:
Although the above may seem a bit confusing at first, it generally does ``the right thing'' in most situations. This determination of the default values to use is based upon the following typical Unix conventions:
pod2usage doesn't force the above conventions upon you, but it will use them by default if you don't expressly tell it to do otherwise. The ability of pod2usage() to accept a single number or a string makes it convenient to use as an innocent looking error message handling function:
use Pod::Usage; use Getopt::Long; ## Parse options GetOptions("help", "man", "flag1") || pod2usage(2); pod2usage(1) if ($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''. EXAMPLESEach 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 UseMost 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 CAVEATSBy 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"); AUTHORBrad Appleton <bradapp@enteract.com>Based on code for Pod::Text::pod2text() written by Tom Christiansen <tchrist@mox.perl.com> ACKNOWLEDGEMENTSSteven McDougall <swmcd@world.std.com> for his help and patience with re-writing this manpage.
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