Module Getopt::Long - extended processing of command line options

Module Getopt::Long implements an extended getopt function called GetOptions(). This function implements the POSIX standard for command line options, with GNU extensions, while still capable of handling the traditional one-letter options.
In general, this means that command line options can have long names instead of single letters, and are introduced with a double dash `--'.

Optionally, Getopt::Long can support the traditional bundling of single-letter command line options.

Getopt::Long is part of the Perl 5 distribution. It is the successor of newgetopt.pl that came with Perl 4. It is fully upward compatible. In fact, the Perl 5 version of newgetopt.pl is just a wrapper around the module.

For complete documentation, see the Getopt::Long POD document or use the command

perldoc Getopt::Long

FEATURES

• Long option names

Major advantage of using long option names is that it is much easier to memorize the option names. Using single-letter names one quickly runs into the problem that there is no logical relationship between the semantics of the selected option and its option letter. Disadvantage is that it requires more typing. Getopt::Long provides for option name abbreviation, so option names may be abbreviated to uniqueness. Also, modern shells like Cornell's tcsh support option name completion. As a rule of thumb, you can use abbreviations freely while running commands interactively but always use the full names in scripts.

Examples (POSIX):

--long --width=80 --height=24

Extensions

-long (convenience) +width=80 (deprecated) -height 24 (traditional)

By default, long option names are case insensitive.

• Single-letter options and bundling

When single-letter options are requested, Getopt::Long allows the option names to be bundled, e.g. "-abc" is equivalent to "-a -b -c". In this case, long option names must be introduced with the POSIX "--" introducer.

Examples

-lgAd (bundle) -xw 80 (bundle, w takes a value) -xw80 (same) even -l24w80 (l = 24 and w = 80)

By default, single-letter option names are case sensitive.

• Flexibility:
  • options can have alternative names, using an alternative name will behave as if the primary name was used;
  • options can be negatable, e.g. "debug" will switch it on, while "nodebug" will switch it off.
  • options can set values, but also add values producing an array of values instead of a single scalar value, or set values in a hash.
  • options can have multiple values, e.g., "--position 25 624".
• Options linkage

Using Getopt::Long gives the programmer ultimate control over the command line options and how they must be handled:

• by setting a global variable in the calling program;
• by setting a specified variable;
• by entering the option name and the value in an associative array (hash) or object (if it is a blessed hash);
• by calling a user-specified subroutine with the option name and the value as arguments (for hash options: the name, key and value);
• combinations of the above.
  • Customization:

The module can be customized by specifying settings in the 'use' directive, or by calling a special method, Getopt::Long::Configure. For example, the following two cases are functionally equal:

use Getopt::Long qw(:config bundling no_ignore_case);

and

use Getopt::Long;
Getopt::Long::Configure qw(bundling no_ignore_case);

Some of the possible customizations. Most of them take a "no_" prefix to reverse the effect:

• default

Restore default settings.

• auto_abbrev

Allow option names to be abbreviated to uniqueness.

• getopt_compat

Allow '+' to start options.

• gnu_compat

Compatibility with GNU getopt_long().

• permute
• require_order

Whether non-options are allowed to be mixed with options.

permute means that

-foo arg1 -bar arg2 arg3

is equivalent to

-foo -bar arg1 arg2 arg3

(provided -foo does not take an argument value).

        require_order means that options processing
        terminates when the first non-option is encountered.

            -foo arg1 -bar arg2 arg3

        is equivalent to

            -foo -- arg1 -bar arg2 arg3

• bundling

        Setting this variable to a non-zero value will allow 
        single-character options to be bundled. To distinguish bundles
        from long option names, long options must be introduced with 
        "--" and single-character options (and bundles) with "-".

• ignore_case

Ignore case when matching options.

• pass_through

        Do not issue error messages for unknown options, but leave
        them (pass-through) in @ARGV.

• prefix

The string that starts options. See also prefix_pattern.

• prefix_pattern

        A Perl pattern that identifies the strings that introduce
        options. Default is --|-|\+ unless environment variable
        POSIXLY_CORRECT has been set, in which case it is --|-.

• long_prefix_pattern

        A perl pattern that is used to identify which prefixes
        should be treated as long style. Any prefixes that don't
        match this pattern will have short option semantics.
        Defaults to --.

• debug

Enable copious debugging output.

• Object oriented interface:

Using the object oriented interface, multiple parser objects can be instantiated, each having their own configuration settings:

$p1 = new Getopt::Long::Parser (config => ["bundling"]); $p2 = new Getopt::Long::Parser (config => ["posix"]); if ($p1->getoptions(...options descriptions...)) ...

AVAILABILITY

The official version for module Getopt::Long comes with the Perl 5 distribution.
Newer versions will be made available on the Comprehensive Perl Archive Network (CPAN), see "http://www.perl.com/CPAN/authors/Johan_Vromans". Or use the CPAN search engine:
http://search.cpan.org/search?mode=module&query=Getopt::Long http://search.cpan.org/search?module=Getopt::Long

COPYRIGHT AND DISCLAIMER

Module Getopt::Long is Copyright 2009,1990 by Johan Vromans. This program is free software; you can redistribute it and/or modify it under the terms of the Perl Artistic License or the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

Johan Vromans                                  jvromans@squirrel.nl
Squirrel Consultancy                         Exloo, the Netherlands
http://www.squirrel.nl       http://www.squirrel.nl/people/jvromans

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