long.pm

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A trivial application of this mechanism is to implement options that
are related to each other. For example:

    my $verbose = '';	# option variable with default value (false)
    GetOptions ('verbose' => \$verbose,
	        'quiet'   => sub { $verbose = 0 });

Here C<--verbose> and C<--quiet> control the same variable
C<$verbose>, but with opposite values.

If the subroutine needs to signal an error, it should call die() with
the desired error message as its argument. GetOptions() will catch the
die(), issue the error message, and record that an error result must
be returned upon completion.

If the text of the error message starts with an exclamation mark C<!>
it is interpreted specially by GetOptions(). There is currently one
special command implemented: C<die("!FINISH")> will cause GetOptions()
to stop processing options, as if it encountered a double dash C<-->.

=head2 Options with multiple names

Often it is user friendly to supply alternate mnemonic names for
options. For example C<--height> could be an alternate name for
C<--length>. Alternate names can be included in the option
specification, separated by vertical bar C<|> characters. To implement
the above example:

    GetOptions ('length|height=f' => \$length);

The first name is called the I<primary> name, the other names are
called I<aliases>. When using a hash to store options, the key will
always be the primary name.

Multiple alternate names are possible.

=head2 Case and abbreviations

Without additional configuration, GetOptions() will ignore the case of
option names, and allow the options to be abbreviated to uniqueness.

    GetOptions ('length|height=f' => \$length, "head" => \$head);

This call will allow C<--l> and C<--L> for the length option, but
requires a least C<--hea> and C<--hei> for the head and height options.

=head2 Summary of Option Specifications

Each option specifier consists of two parts: the name specification
and the argument specification.

The name specification contains the name of the option, optionally
followed by a list of alternative names separated by vertical bar
characters.

    length	      option name is "length"
    length|size|l     name is "length", aliases are "size" and "l"

The argument specification is optional. If omitted, the option is
considered boolean, a value of 1 will be assigned when the option is
used on the command line.

The argument specification can be

=over 4

=item !

The option does not take an argument and may be negated by prefixing
it with "no" or "no-". E.g. C<"foo!"> will allow C<--foo> (a value of
1 will be assigned) as well as C<--nofoo> and C<--no-foo> (a value of
0 will be assigned). If the option has aliases, this applies to the
aliases as well.

Using negation on a single letter option when bundling is in effect is
pointless and will result in a warning.

=item +

The option does not take an argument and will be incremented by 1
every time it appears on the command line. E.g. C<"more+">, when used
with C<--more --more --more>, will increment the value three times,
resulting in a value of 3 (provided it was 0 or undefined at first).

The C<+> specifier is ignored if the option destination is not a scalar.

=item = I<type> [ I<desttype> ] [ I<repeat> ]

The option requires an argument of the given type. Supported types
are:

=over 4

=item s

String. An arbitrary sequence of characters. It is valid for the
argument to start with C<-> or C<-->.

=item i

Integer. An optional leading plus or minus sign, followed by a
sequence of digits.

=item o

Extended integer, Perl style. This can be either an optional leading
plus or minus sign, followed by a sequence of digits, or an octal
string (a zero, optionally followed by '0', '1', .. '7'), or a
hexadecimal string (C<0x> followed by '0' .. '9', 'a' .. 'f', case
insensitive), or a binary string (C<0b> followed by a series of '0'
and '1').

=item f

Real number. For example C<3.14>, C<-6.23E24> and so on.

=back

The I<desttype> can be C<@> or C<%> to specify that the option is
list or a hash valued. This is only needed when the destination for
the option value is not otherwise specified. It should be omitted when
not needed.

The I<repeat> specifies the number of values this option takes per
occurrence on the command line. It has the format C<{> [ I<min> ] [ C<,> [ I<max> ] ] C<}>.

I<min> denotes the minimal number of arguments. It defaults to 1 for
options with C<=> and to 0 for options with C<:>, see below. Note that
I<min> overrules the C<=> / C<:> semantics.

I<max> denotes the maximum number of arguments. It must be at least
I<min>. If I<max> is omitted, I<but the comma is not>, there is no
upper bound to the number of argument values taken.

=item : I<type> [ I<desttype> ]

Like C<=>, but designates the argument as optional.
If omitted, an empty string will be assigned to string values options,
and the value zero to numeric options.

Note that if a string argument starts with C<-> or C<-->, it will be
considered an option on itself.

=item : I<number> [ I<desttype> ]

Like C<:i>, but if the value is omitted, the I<number> will be assigned.

=item : + [ I<desttype> ]

Like C<:i>, but if the value is omitted, the current value for the
option will be incremented.

=back

=head1 Advanced Possibilities

=head2 Object oriented interface

Getopt::Long can be used in an object oriented way as well:

    use Getopt::Long;
    $p = new Getopt::Long::Parser;
    $p->configure(...configuration options...);
    if ($p->getoptions(...options descriptions...)) ...

Configuration options can be passed to the constructor:

    $p = new Getopt::Long::Parser
             config => [...configuration options...];

=head2 Thread Safety

Getopt::Long is thread safe when using ithreads as of Perl 5.8.  It is
I<not> thread safe when using the older (experimental and now
obsolete) threads implementation that was added to Perl 5.005.

=head2 Documentation and help texts

Getopt::Long encourages the use of Pod::Usage to produce help
messages. For example:

    use Getopt::Long;
    use Pod::Usage;

    my $man = 0;
    my $help = 0;

    GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
    pod2usage(1) if $help;
    pod2usage(-exitstatus => 0, -verbose => 2) if $man;

    __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

See L<Pod::Usage> for details.

=head2 Parsing options from an arbitrary array

By default, GetOptions parses the options that are present in the
global array C<@ARGV>. A special entry C<GetOptionsFromArray> can be
used to parse options from an arbitrary array.

    use Getopt::Long qw(GetOptionsFromArray);
    $ret = GetOptionsFromArray(\@myopts, ...);

When used like this, the global C<@ARGV> is not touched at all.

The following two calls behave identically:

    $ret = GetOptions( ... );
    $ret = GetOptionsFromArray(\@ARGV, ... );

=head2 Parsing options from an arbitrary string

A special entry C<GetOptionsFromString> can be used to parse options
from an arbitrary string.

    use Getopt::Long qw(GetOptionsFromString);
    $ret = GetOptionsFromString($string, ...);

The contents of the string are split into arguments using a call to
C<Text::ParseWords::shellwords>. As with C<GetOptionsFromArray>, the
global C<@ARGV> is not touched.

It is possible that, upon completion, not all arguments in the string
have been processed. C<GetOptionsFromString> will, when called in list
context, return both the return status and an array reference to any
remaining arguments:

    ($ret, $args) = GetOptionsFromString($string, ... );

If any arguments remain, and C<GetOptionsFromString> was not called in
list context, a message will be given and C<GetOptionsFromString> will
return failure.

=head2 Storing options values in a hash

Sometimes, for example when there are a lot of options, having a
separate variable for each of them can be cumbersome. GetOptions()
supports, as an alternative mechanism, storing options values in a
hash.

To obtain this, a reference to a hash must be passed I<as the first
argument> to GetOptions(). For each option that is specified on the
command line, the option value will be stored in the hash with the
option name as key. Options that are not actually used on the command
line will not be put in the hash, on other words,
C<exists($h{option})> (or defined()) can be used to test if an option
was used. The drawback is that warnings will be issued if the program
runs under C<use strict> and uses C<$h{option}> without testing with
exists() or defined() first.

    my %h = ();
    GetOptions (\%h, 'length=i');	# will store in $h{length}

For options that take list or hash values, it is necessary to indicate
this by appending an C<@> or C<%> sign after the type:

    GetOptions (\%h, 'colours=s@');	# will push to @{$h{colours}}

To make things more complicated, the hash may contain references to
the actual destinations, for example:

    my $len = 0;
    my %h = ('length' => \$len);
    GetOptions (\%h, 'length=i');	# will store in $len

This example is fully equivalent with:

    my $len = 0;
    GetOptions ('length=i' => \$len);	# will store in $len

Any mixture is possible. For example, the most frequently used options
could be stored in variables while all other options get stored in the
hash:

    my $verbose = 0;			# frequently referred
    my $debug = 0;			# frequently referred
    my %h = ('verbose' => \$verbose, 'debug' => \$debug);
    GetOptions (\%h, 'verbose', 'debug', 'filter', 'size=i');
    if ( $verbose ) { ... }
    if ( exists $h{filter} ) { ... option 'filter' was specified ... }

=head2 Bundling

With bundling it is possible to set several single-character options
at once. For example if C<a>, C<v> and C<x> are all valid options,

    -vax

would set all three.

Getopt::Long supports two levels of bundling. To enable bundling, a
call to Getopt::Long::Configure is required.

The first level of bundling can be enabled with:

    Getopt::Long::Configure ("bundling");

Configured this way, single-character options can be bundled but long
options B<must> always start with a double dash C<--> to avoid
ambiguity. For example, when C<vax>, C<a>, C<v> and C<x> are all valid
options,

    -vax

would set C<a>, C<v> and C<x>, but

    --vax

would set C<vax>.

The second level of bundling lifts this restriction. It can be enabled
with:

    Getopt::Long::Configure ("bundling_override");

Now, C<-vax> would set the option C<vax>.

When any level of bundling is enabled, option values may be inserted
in the bundle. For example:

    -h24w80

is equivalent to

    -h 24 -w 80

When configured for bundling, single-character options are matched
case sensitive while long options are matched case insensitive. To
have the single-character options matched case insensitive as well,
use:

    Getopt::Long::Configure ("bundling", "ignorecase_always");

It goes without saying that bundling can be quite confusing.

=head2 The lonesome dash

Normally, a lone dash C<-> on the command line will not be considered
an option. Option processing will terminate (unless "permute" is
configured) and the dash will be left in C<@ARGV>.

It is possible to get special treatment for a lone dash. This can be
achieved by adding an option specification with an empty name, for
example:

    GetOptions ('' => \$stdio);

A lone dash on the command line will now be a legal option, and using
it will set variable C<$stdio>.

=head2 Argument callback

A special option 'name' C<< <> >> can be used to designate a subroutine
to handle non-option arguments. When GetOptions() encounters an
argument that does not look like an option, it will immediately call this
subroutine and passes it one parameter: the argument name.

For example:

    my $width = 80;
    sub process { ... }
    GetOptions ('width=i' => \$width, '<>' => \&process);

When applied to the following command line:

    arg1 --width=72 arg2 --width=60 arg3

This will call
C<process("arg1")> while C<$width> is C<80>,
C<process("arg2")> while C<$width> is C<72>, and
C<process("arg3")> while C<$width> is C<60>.

This feature requires configuration option B<permute>, see section
L<Configuring Getopt::Long>.

=head1 Configuring Getopt::Long

Getopt::Long can be configured by calling subroutine
Getopt::Long::Configure(). This subroutine takes a list of quoted
strings, each specifying a configuration option to be enabled, e.g.
C<ignore_case>, or disabled, e.g. C<no_ignore_case>. Case does not
matter. Multiple calls to Configure() are possible.

Alternatively, as of version 2.24, the configuration options may be
passed together with the C<use> statement:

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

The following options are available:

=over 12

=item default

This option causes all configuration options to be reset to their
default values.

=item posix_default

This option causes all configuration options to be reset to their
default values as if the environment variable POSIXLY_CORRECT had
been set.

=item auto_abbrev

Allow optio