source: trunk/essentials/dev-lang/perl/lib/Getopt/Long/README@ 3296

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::GetOptions() 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 2005,1990 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                                  [email protected]
Squirrel Consultancy                         Exloo, the Netherlands
http://www.squirrel.nl       http://www.squirrel.nl/people/jvromans
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