Ilya Zakharevich

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 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. 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. 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 --, 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];

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 or a reference to a subroutine.

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 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 op 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 on configuration variable $Getopt::Long::autoabbrev.

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 $Getopt::Long::order to have the value $PERMUTE. 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 value

A return status of 0 (false) indicates that the function detected one or more errors.

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. This only applies if no linkage is supplied.

If configuration variable $Getopt::Long::getopt_compat is set to a non-zero value, options that start with "+" 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 variabel 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:

   $bar = '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 VARIABLES

The following variables can be set to change the default behaviour of GetOptions():

$Getopt::Long::autoabbrev

Allow option names to be abbreviated to uniqueness. Default is 1 unless environment variable POSIXLY_CORRECT has been set.

$Getopt::Long::getopt_compat

Allow '+' to start options. Default is 1 unless environment variable POSIXLY_CORRECT has been set.

$Getopt::Long::order

Whether non-options are allowed to be mixed with options. Default is $REQUIRE_ORDER if environment variable POSIXLY_CORRECT has been set, $PERMUTE otherwise.

$PERMUTE 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 $Getopt::Long::order is $REQUIRE_ORDER, options processing terminates when the first non-option is encountered.

    -foo arg1 -bar arg2 arg3

is equivalent to

    -foo -- arg1 -bar arg2 arg3

$RETURN_IN_ORDER is not supported by GetOptions().

$Getopt::Long::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 -. 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; this value has to be the last part of the bundle, e.g.

    scale -h24 -w80

is equivalent to

    scale -h 24 -w 80

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

$Getopt::Long::ignorecase

Ignore case when matching options. Default is 1. When bundling is in effect, case is ignored on single-character options only if $Getopt::Long::ignorecase is greater than 1.

$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 2.00;

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.

$Getopt::Long::debug

Enable copious debugging output. Default is 0.