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perlman:Getopt::Long

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on Dec 23, 1999 at 00:51 UTC ( #1211=perlfunc: print w/ replies, xml ) Need Help??

Getopt::Long

See the current Perl documentation for Getopt::Long.

Here is our local, out-dated (pre-5.6) version:


GetOptions - extended processing of command line options



  use Getopt::Long;
  $result = GetOptions (...option-descriptions...);



The Getopt::Long module implements an extended getopt function called GetOptions(). This function adheres to the POSIX syntax for command line options, with GNU extensions. In general, this means that options have long names instead of single letters, and are introduced with a double dash ``--''. Support for bundling of command line options, as was the case with the more traditional single-letter approach, is provided but not enabled by default. For example, the UNIX ``ps'' command can be given the command line ``option''

  -vax

which means the combination of -v, -a and -x. With the new syntax --vax would be a single option, probably indicating a computer architecture.

Command line options can be used to set values. These values can be specified in one of two ways:

  --size 24
  --size=24

GetOptions is called with a list of option-descriptions, each of which consists of two elements: the option specifier and the option linkage. The option specifier defines the name of the option and, optionally, the value it can take. The option linkage is usually a reference to a variable that will be set when the option is used. For example, the following call to GetOptions:

  GetOptions("size=i" => \$offset);

will accept a command line option ``size'' that must have an integer value. With a command line of ``--size 24'' this will cause the variable $offset to get the value 24.

Alternatively, the first argument to GetOptions may be a reference to a HASH describing the linkage for the options, or an object whose class is based on a HASH. The following call is equivalent to the example above:

  %optctl = ("size" => \$offset);
  GetOptions(\%optctl, "size=i");

Linkage may be specified using either of the above methods, or both. Linkage specified in the argument list takes precedence over the linkage specified in the HASH.

The command line options are taken from array @ARGV. Upon completion of GetOptions, @ARGV will contain the rest (i.e. the non-options) of the command line. Each option specifier designates the name of the option, optionally followed by an argument specifier.

Options that do not take arguments will have no argument specifier. The option variable will be set to 1 if the option is used.

For the other options, the values for argument specifiers are:

!

Option does not take an argument and may be negated, i.e. prefixed by ``no''. E.g. ``foo!'' will allow --foo (with value 1) and -nofoo (with value 0). The option variable will be set to 1, or 0 if negated.

+

Option does not take an argument and will be incremented by 1 every time it appears on the command line. E.g. ``more+'', when used with --more --more --more, will set the option variable to 3 (provided it was 0 or undefined at first).

The + specifier is ignored if the option destination is not a SCALAR.

=s

Option takes a mandatory string argument. This string will be assigned to the option variable. Note that even if the string argument starts with - or --, it will not be considered an option on itself.

:s

Option takes an optional string argument. This string will be assigned to the option variable. If omitted, it will be assigned ``'' (an empty string). If the string argument starts with - or --, it will be considered an option on itself.

=i

Option takes a mandatory integer argument. This value will be assigned to the option variable. Note that the value may start with - to indicate a negative value.

:i

Option takes an optional integer argument. This value will be assigned to the option variable. If omitted, the value 0 will be assigned. Note that the value may start with - to indicate a negative value.

=f

Option takes a mandatory real number argument. This value will be assigned to the option variable. Note that the value may start with - to indicate a negative value.

:f

Option takes an optional real number argument. This value will be assigned to the option variable. If omitted, the value 0 will be assigned.

A lone dash - is considered an option, the corresponding option name is the empty string.

A double dash on itself -- signals end of the options list.


Linkage specification

The linkage specifier is optional. If no linkage is explicitly specified but a ref HASH is passed, GetOptions will place the value in the HASH. For example:

  %optctl = ();
  GetOptions (\%optctl, "size=i");

will perform the equivalent of the assignment

  $optctl{"size"} = 24;

For array options, a reference to an array is used, e.g.:

  %optctl = ();
  GetOptions (\%optctl, "sizes=i@");

with command line ``-sizes 24 -sizes 48'' will perform the equivalent of the assignment

  $optctl{"sizes"} = [24, 48];

For hash options (an option whose argument looks like ``name=value''), a reference to a hash is used, e.g.:

  %optctl = ();
  GetOptions (\%optctl, "define=s%");

with command line ``--define foo=hello --define bar=world'' will perform the equivalent of the assignment

  $optctl{"define"} = {foo=>'hello', bar=>'world')

If no linkage is explicitly specified and no ref HASH is passed, GetOptions will put the value in a global variable named after the option, prefixed by ``opt_''. To yield a usable Perl variable, characters that are not part of the syntax for variables are translated to underscores. For example, ``--fpp-struct-return'' will set the variable $opt_fpp_struct_return. Note that this variable resides in the namespace of the calling program, not necessarily main. For example:

  GetOptions ("size=i", "sizes=i@");

with command line ``-size 10 -sizes 24 -sizes 48'' will perform the equivalent of the assignments

  $opt_size = 10;
  @opt_sizes = (24, 48);

A lone dash - is considered an option, the corresponding Perl identifier is $opt_ .

The linkage specifier can be a reference to a scalar, a reference to an array, a reference to a hash or a reference to a subroutine.

Note that, if your code is running under the recommended use strict 'vars' pragma, it may be helpful to declare these package variables via use vars perhaps something like this:

  use vars qw/ $opt_size @opt_sizes $opt_bar /;

If a REF SCALAR is supplied, the new value is stored in the referenced variable. If the option occurs more than once, the previous value is overwritten.

If a REF ARRAY is supplied, the new value is appended (pushed) to the referenced array.

If a REF HASH is supplied, the option value should look like ``key'' or ``key=value'' (if the ``=value'' is omitted then a value of 1 is implied). In this case, the element of the referenced hash with the key ``key'' is assigned ``value''.

If a REF CODE is supplied, the referenced subroutine is called with two arguments: the option name and the option value. The option name is always the true name, not an abbreviation or alias.


Aliases and abbreviations

The option name may actually be a list of option names, separated by ``|''s, e.g. ``foo|bar|blech=s''. In this example, ``foo'' is the true name of this option. If no linkage is specified, options ``foo'', ``bar'' and ``blech'' all will set $opt_foo. For convenience, the single character ``?'' is allowed as an alias, e.g. ``help|?''.

Option names may be abbreviated to uniqueness, depending on configuration option auto_abbrev.


Non-option call-back routine

A special option specifier, <>, can be used to designate a subroutine to handle non-option arguments. GetOptions will immediately call this subroutine for every non-option it encounters in the options list. This subroutine gets the name of the non-option passed. This feature requires configuration option permute, see section CONFIGURATION OPTIONS.

See also the examples.


Option starters

On the command line, options can start with - (traditional), -- (POSIX) and + (GNU, now being phased out). The latter is not allowed if the environment variable POSIXLY_CORRECT has been defined.

Options that start with ``--'' may have an argument appended, separated with an ``='', e.g. ``--foo=bar''.


Return values and Errors

Configuration errors and errors in the option definitions are signalled using die and will terminate the calling program unless the call to Getopt::Long::GetOptions() was embedded in eval or die was trapped using $SIG{__DIE__}.

A return value of 1 (true) indicates success.

A return status of 0 (false) indicates that the function detected one or more errors during option parsing. These errors are signalled using perlguts and can be trapped with $SIG{__WARN__}.

Errors that can't happen are signalled using Carp::croak().


COMPATIBILITY

Getopt::Long::GetOptions() 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.

If an ``@'' sign is appended to the argument specifier, the option is treated as an array. Value(s) are not set, but pushed into array @opt_name. If explicit linkage is supplied, this must be a reference to an ARRAY.

If an ``%'' sign is appended to the argument specifier, the option is treated as a hash. Value(s) of the form ``name=value'' are set by setting the element of the hash %opt_name with key ``name'' to ``value'' (if the ``=value'' portion is omitted it defaults to 1). If explicit linkage is supplied, this must be a reference to a HASH.

If configuration option getopt_compat is set (see section CONFIGURATION OPTIONS), options that start with ``+'' or ``-'' may also include their arguments, e.g. ``+foo=bar''. This is for compatiblity with older implementations of the GNU ``getopt'' routine.

If the first argument to GetOptions is a string consisting of only non-alphanumeric characters, it is taken to specify the option starter characters. Everything starting with one of these characters from the starter will be considered an option. Using a starter argument is strongly deprecated.

For convenience, option specifiers may have a leading - or --, so it is possible to write:

   GetOptions qw(-foo=s --bar=i --ar=s);


EXAMPLES

If the option specifier is ``one:i'' (i.e. takes an optional integer argument), then the following situations are handled:

   -one -two            -> $opt_one = '', -two is next option
   -one -2              -> $opt_one = -2

Also, assume specifiers ``foo=s'' and ``bar:s'' :

   -bar -xxx            -> $opt_bar = '', '-xxx' is next option
   -foo -bar            -> $opt_foo = '-bar'
   -foo --              -> $opt_foo = '--'

In GNU or POSIX format, option names and values can be combined:

   +foo=blech           -> $opt_foo = 'blech'
   --bar=               -> $opt_bar = ''
   --bar=--             -> $opt_bar = '--'

Example of using variable references:

   $ret = GetOptions ('foo=s', \$foo, 'bar=i', 'ar=s', \@ar);

With command line options ``-foo blech -bar 24 -ar xx -ar yy'' this will result in:

   $foo = 'blech'
   $opt_bar = 24
   @ar = ('xx','yy')

Example of using the <> option specifier:

   @ARGV = qw(-foo 1 bar -foo 2 blech);
   GetOptions("foo=i", \$myfoo, "<>", \&mysub);

Results:

   mysub("bar") will be called (with $myfoo being 1)
   mysub("blech") will be called (with $myfoo being 2)

Compare this with:

   @ARGV = qw(-foo 1 bar -foo 2 blech);
   GetOptions("foo=i", \$myfoo);

This will leave the non-options in @ARGV:

   $myfoo -> 2
   @ARGV -> qw(bar blech)


CONFIGURATION OPTIONS

GetOptions can be configured by calling subroutine Getopt::Long::Configure. This subroutine takes a list of quoted strings, each specifying a configuration option to be set, e.g. ignore_case. Options can be reset by prefixing with no_, e.g. no_ignore_case. Case does not matter. Multiple calls to config are possible.

Previous versions of Getopt::Long used variables for the purpose of configuring. Although manipulating these variables still work, it is strongly encouraged to use the new config routine. Besides, it is much easier.

The following options are available:

default

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

auto_abbrev

Allow option names to be abbreviated to uniqueness. Default is set unless environment variable POSIXLY_CORRECT has been set, in which case auto_abbrev is reset.

getopt_compat

Allow '+' to start options. Default is set unless environment variable POSIXLY_CORRECT has been set, in which case getopt_compat is reset.

require_order

Whether non-options are allowed to be mixed with options. Default is set unless environment variable POSIXLY_CORRECT has been set, in which case b<require_order> is reset.

See also permute, which is the opposite of require_order.

permute

Whether non-options are allowed to be mixed with options. Default is set unless environment variable POSIXLY_CORRECT has been set, in which case permute is reset. Note that permute is the opposite of require_order.

If permute is set, this means that

    -foo arg1 -bar arg2 arg3

is equivalent to

    -foo -bar arg1 arg2 arg3

If a non-option call-back routine is specified, @ARGV will always be empty upon succesful return of GetOptions since all options have been processed, except when -- is used:

    -foo arg1 -bar arg2 -- arg3

will call the call-back routine for arg1 and arg2, and terminate leaving arg2 in @ARGV.

If require_order is set, options processing terminates when the first non-option is encountered.

    -foo arg1 -bar arg2 arg3

is equivalent to

    -foo -- arg1 -bar arg2 arg3
bundling (default: reset)

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 -. For example,

    ps -vax --vax

would be equivalent to

    ps -v -a -x --vax

provided ``vax'', ``v'', ``a'' and ``x'' have been defined to be valid options.

Bundled options can also include a value in the bundle; for strings this value is the rest of the bundle, but integer and floating values may be combined in the bundle, e.g.

    scale -h24w80

is equivalent to

    scale -h 24 -w 80

Note: resetting bundling also resets bundling_override.

bundling_override (default: reset)

If bundling_override is set, bundling is enabled as with bundling but now long option names override option bundles. In the above example, -vax would be interpreted as the option ``vax'', not the bundle ``v'', ``a'', ``x''.

Note: resetting bundling_override also resets bundling.

Note: Using option bundling can easily lead to unexpected results, especially when mixing long options and bundles. Caveat emptor.

ignore_case (default: set)

If set, case is ignored when matching options.

Note: resetting ignore_case also resets ignore_case_always.

ignore_case_always (default: reset)

When bundling is in effect, case is ignored on single-character options also.

Note: resetting ignore_case_always also resets ignore_case.

pass_through (default: reset)

Unknown options are passed through in @ARGV instead of being flagged as errors. This makes it possible to write wrapper scripts that process only part of the user supplied options, and passes the remaining options to some other program.

This can be very confusing, especially when permute is also set.

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 (--|-).

debug (default: reset)

Enable copious debugging output.


OTHER USEFUL VARIABLES

$Getopt::Long::VERSION

The version number of this Getopt::Long implementation in the format major.minor. This can be used to have Exporter check the version, e.g.

    use Getopt::Long 3.00;

You can inspect $Getopt::Long::major_version and $Getopt::Long::minor_version for the individual components.

$Getopt::Long::error

Internal error flag. May be incremented from a call-back routine to cause options parsing to fail.


AUTHOR

Johan Vromans <jvromans@squirrel.nl>


COPYRIGHT AND DISCLAIMER

This program is Copyright 1990,1998 by Johan Vromans. This program is free software; you can redistribute it and/or modify it under the terms of 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.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

If you do not have a copy of the GNU General Public License write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.


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