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Getopt::Long

Section: Perl Programmers Reference Guide (3)
Updated: perl 5.004, patch 04
Index

NAME

GetOptions - extended processing of command line options

SYNOPSIS

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

DESCRIPTION

The Getopt::Long module implements an extended getopt function calledGetOptions(). This function adheres to the POSIX syntax for commandline options, with GNU extensions. In general, this means that optionshave long names instead of single letters, and are introduced with adouble dash ``--''. Support for bundling of command line options, as wasthe case with the more traditional single-letter approach, is providedbut not enabled by default. For example, the UNIX ``ps'' command can begiven the command line ``option''

  -vax

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

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

  --size 24  --size=24

GetOptions is called with a list of option-descriptions, each of whichconsists 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 avariable that will be set when the option is used. For example, thefollowing call to GetOptions:

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

will accept a command line option ``size'' that must have an integervalue. 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 toa HASH describing the linkage for the options, or an object whoseclass is based on a HASH. The following call is equivalent to theexample 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 thelinkage specified in the HASH.

The command line options are taken from array @ARGV. Upon completionof GetOptions, @ARGV will contain the rest (i.e. the non-options) ofthe command line.
Each option specifier designates the name of the option, optionallyfollowed by an argument specifier. Values for argument specifiers are:

<none>: Option does not take an argument. The option variable will be set to 1.
!: 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.
=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 --, itwill 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 --, itwill 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 negativevalue.
: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 negativevalue.
=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 negativevalue.
: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 optionname 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 explicitlyspecified but a ref HASH is passed, GetOptions will place the value inthe 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 ofthe 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 theequivalent 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 theoption, prefixed by ``opt_''. To yield a usable Perl variable,characters that are not part of the syntax for variables aretranslated to underscores. For example, ``---fpp-struct-return'' will setthe variable $opt_fpp_struct_return. Note that this variable residesin 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 theequivalent of the assignments

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

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

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

If a REF SCALAR is supplied, the new value is stored in the referencedvariable. If the option occurs more than once, the previous value isoverwritten.

If a REF ARRAY is supplied, the new value is appended (pushed) to thereferenced 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 withtwo 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 nameof this option. If no linkage is specified, options ``foo'', ``bar'' and``blech'' all will set $opt_foo.

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

Non-option call-back routine

A special option specifier, <>, can be used to designate a subroutineto handle non-option arguments. GetOptions will immediately call thissubroutine 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 sectionCONFIGURATION OPTIONS.

COMPATIBILITY

Getopt::Long::GetOptions() is the successor ofnewgetopt.pl that came with Perl 4. It is fully upward compatible.In fact, the Perl 5 version of newgetopt.pl is just a wrapper aroundthe module.

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

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

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

If the first argument to GetOptions is a string consisting of onlynon-alphanumeric characters, it is taken to specify the option startercharacters. Everything starting with one of these characters from thestarter will be considered an option. Using a starter argument isstrongly 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 integerargument), 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 subroutineGetopt::Long::config. This subroutine takes a list of quotedstrings, 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 configare possible.

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

The following options are available:

default

This option causes all configuration options to be reset to theirdefault values.

auto_abbrev

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

getopt_compat

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

require_order

Whether non-options are allowed to be mixed withoptions.Default is set unless environment variablePOSIXLY_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 withoptions.Default is set unless environment variablePOSIXLY_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 beempty upon succesful return of GetOptions since all options have beenprocessed, except when -- is used:

    -foo arg1 -bar arg2 -- arg3

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

If require_order is set, options processingterminates 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-characteroptions to be bundled. To distinguish bundles from long option names,long options must be introduced with -- and single-characteroptions (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 validoptions.

Bundled options can also include a value in the bundle; this value hasto be the last part of the bundle, e.g.

    scale -h24 -w80

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 withbundling but now long option names override option bundles. In theabove example, -vax would be interpreted as the option ``vax'', notthe 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-characteroptions also.

Note: resetting ignore_case_always also resets ignore_case.

pass_through (default: reset)

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

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

debug (default: reset)

Enable copious debugging output.

OTHER USEFUL VARIABLES

$Getopt::Long::VERSION

The version number of this Getopt::Long implementation in the formatmajor.minor. This can be used to have Exporter check theversion, 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 tocause options parsing to fail.

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