Getopt::Long(3p) Perl Programmers Reference Guide Getopt::Long(3p)

Getopt::Long(3p) Perl Programmers Reference Guide Getopt::Long(3p) #

Getopt::Long(3p) Perl Programmers Reference Guide Getopt::Long(3p)

NNAAMMEE #

 Getopt::Long - Extended processing of command line options

SSYYNNOOPPSSIISS #

   use Getopt::Long;
   my $data   = "file.dat";
   my $length = 24;
   my $verbose;
   GetOptions ("length=i" => \$length,    # numeric
               "file=s"   => \$data,      # string
               "verbose"  => \$verbose)   # flag
   or die("Error in command line arguments\n");

DDEESSCCRRIIPPTTIIOONN #

 The Getopt::Long module implements an extended getopt function called
 GGeettOOppttiioonnss(()). It parses the command line from @ARGV, recognizing and
 removing specified options and their possible values.

 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.

CCoommmmaanndd LLiinnee OOppttiioonnss,, aann IInnttrroodduuccttiioonn Command line operated programs traditionally take their arguments from the command line, for example filenames or other information that the program needs to know. Besides arguments, these programs often take command line _o_p_t_i_o_n_s as well. Options are not necessary for the program to work, hence the name ‘option’, but are used to modify its default behaviour. For example, a program could do its job quietly, but with a suitable option it could provide verbose information about what it did.

 Command line options come in several flavours. Historically, they are
 preceded by a single dash "-", and consist of a single letter.

     -l -a -c

 Usually, these single-character options can be bundled:

     -lac

 Options can have values, the value is placed after the option character.
 Sometimes with whitespace in between, sometimes not:

     -s 24 -s24

 Due to the very cryptic nature of these options, another style was
 developed that used long names. So instead of a cryptic "-l" one could
 use the more descriptive "--long". To distinguish between a bundle of
 single-character options and a long one, two dashes are used to precede
 the option name. Early implementations of long options used a plus "+"
 instead. Also, option values could be specified either like

     --size=24

 or

     --size 24

 The "+" form is now obsolete and strongly deprecated.

GGeettttiinngg SSttaarrtteedd wwiitthh GGeettoopptt::::LLoonngg Getopt::Long is the Perl5 successor of “newgetopt.pl”. This was the first Perl module that provided support for handling the new style of command line options, in particular long option names, hence the Perl5 name Getopt::Long. This module also supports single-character options and bundling.

 To use Getopt::Long from a Perl program, you must include the following
 line in your Perl program:

     use Getopt::Long;

 This will load the core of the Getopt::Long module and prepare your
 program for using it. Most of the actual Getopt::Long code is not loaded
 until you really call one of its functions.

 In the default configuration, options names may be abbreviated to
 uniqueness, case does not matter, and a single dash is sufficient, even
 for long option names. Also, options may be placed between non-option
 arguments. See "Configuring Getopt::Long" for more details on how to
 configure Getopt::Long.

SSiimmppllee ooppttiioonnss The most simple options are the ones that take no values. Their mere presence on the command line enables the option. Popular examples are:

     --all --verbose --quiet --debug

 Handling simple options is straightforward:

     my $verbose = '';   # option variable with default value (false)
     my $all = '';       # option variable with default value (false)
     GetOptions ('verbose' => \$verbose, 'all' => \$all);

 The call to GGeettOOppttiioonnss(()) parses the command line arguments that are
 present in @ARGV and sets the option variable to the value 1 if the
 option did occur on the command line. Otherwise, the option variable is
 not touched. Setting the option value to true is often called _e_n_a_b_l_i_n_g
 the option.

 The option name as specified to the GGeettOOppttiioonnss(()) function is called the
 option _s_p_e_c_i_f_i_c_a_t_i_o_n. Later we'll see that this specification can contain
 more than just the option name. The reference to the variable is called
 the option _d_e_s_t_i_n_a_t_i_o_n.

 GGeettOOppttiioonnss(()) will return a true value if the command line could be
 processed successfully. Otherwise, it will write error messages using
 ddiiee(()) and wwaarrnn(()), and return a false result.

AA lliittttllee bbiitt lleessss ssiimmppllee ooppttiioonnss Getopt::Long supports two useful variants of simple options: _n_e_g_a_t_a_b_l_e options and _i_n_c_r_e_m_e_n_t_a_l options.

 A negatable option is specified with an exclamation mark "!" after the
 option name:

     my $verbose = '';   # option variable with default value (false)
     GetOptions ('verbose!' => \$verbose);

 Now, using "--verbose" on the command line will enable $verbose, as
 expected. But it is also allowed to use "--noverbose", which will disable
 $verbose by setting its value to 0. Using a suitable default value, the
 program can find out whether $verbose is false by default, or disabled by
 using "--noverbose".

 An incremental option is specified with a plus "+" after the option name:

     my $verbose = '';   # option variable with default value (false)
     GetOptions ('verbose+' => \$verbose);

 Using "--verbose" on the command line will increment the value of
 $verbose. This way the program can keep track of how many times the
 option occurred on the command line. For example, each occurrence of
 "--verbose" could increase the verbosity level of the program.

MMiixxiinngg ccoommmmaanndd lliinnee ooppttiioonn wwiitthh ootthheerr aarrgguummeennttss Usually programs take command line options as well as other arguments, for example, file names. It is good practice to always specify the options first, and the other arguments last. Getopt::Long will, however, allow the options and arguments to be mixed and ‘filter out’ all the options before passing the rest of the arguments to the program. To stop Getopt::Long from processing further arguments, insert a double dash “–” on the command line:

     --size 24 -- --all

 In this example, "--all" will _n_o_t be treated as an option, but passed to
 the program unharmed, in @ARGV.

OOppttiioonnss wwiitthh vvaalluueess For options that take values it must be specified whether the option value is required or not, and what kind of value the option expects.

 Three kinds of values are supported: integer numbers, floating point
 numbers, and strings.

 If the option value is required, Getopt::Long will take the command line
 argument that follows the option and assign this to the option variable.
 If, however, the option value is specified as optional, this will only be
 done if that value does not look like a valid command line option itself.

     my $tag = '';       # option variable with default value
     GetOptions ('tag=s' => \$tag);

 In the option specification, the option name is followed by an equals
 sign "=" and the letter "s". The equals sign indicates that this option
 requires a value. The letter "s" indicates that this value is an
 arbitrary string. Other possible value types are "i" for integer values,
 and "f" for floating point values. Using a colon ":" instead of the
 equals sign indicates that the option value is optional. In this case, if
 no suitable value is supplied, string valued options get an empty string
 '' assigned, while numeric options are set to 0.

OOppttiioonnss wwiitthh mmuullttiippllee vvaalluueess Options sometimes take several values. For example, a program could use multiple directories to search for library files:

     --library lib/stdlib --library lib/extlib

 To accomplish this behaviour, simply specify an array reference as the
 destination for the option:

     GetOptions ("library=s" => \@libfiles);

 Alternatively, you can specify that the option can have multiple values
 by adding a "@", and pass a reference to a scalar as the destination:

     GetOptions ("library=s@" => \$libfiles);

 Used with the example above, @libfiles c.q. @$libfiles would contain two
 strings upon completion: "lib/stdlib" and "lib/extlib", in that order. It
 is also possible to specify that only integer or floating point numbers
 are acceptable values.

 Often it is useful to allow comma-separated lists of values as well as
 multiple occurrences of the options. This is easy using Perl's sspplliitt(())
 and jjooiinn(()) operators:

     GetOptions ("library=s" => \@libfiles);
     @libfiles = split(/,/,join(',',@libfiles));

 Of course, it is important to choose the right separator string for each
 purpose.

 Warning: What follows is an experimental feature.

 Options can take multiple values at once, for example

     --coordinates 52.2 16.4 --rgbcolor 255 255 149

 This can be accomplished by adding a repeat specifier to the option
 specification. Repeat specifiers are very similar to the "{...}" repeat
 specifiers that can be used with regular expression patterns.  For
 example, the above command line would be handled as follows:

     GetOptions('coordinates=f{2}' => \@coor, 'rgbcolor=i{3}' => \@color);

 The destination for the option must be an array or array reference.

 It is also possible to specify the minimal and maximal number of
 arguments an option takes. "foo=s{2,4}" indicates an option that takes at
 least two and at most 4 arguments. "foo=s{1,}" indicates one or more
 values; "foo:s{,}" indicates zero or more option values.

OOppttiioonnss wwiitthh hhaasshh vvaalluueess If the option destination is a reference to a hash, the option will take, as value, strings of the form _k_e_y"="_v_a_l_u_e. The value will be stored with the specified key in the hash.

     GetOptions ("define=s" => \%defines);

 Alternatively you can use:

     GetOptions ("define=s%" => \$defines);

 When used with command line options:

     --define os=linux --define vendor=redhat

 the hash %defines (or %$defines) will contain two keys, "os" with value
 "linux" and "vendor" with value "redhat". It is also possible to specify
 that only integer or floating point numbers are acceptable values. The
 keys are always taken to be strings.

UUsseerr--ddeeffiinneedd ssuubbrroouuttiinneess ttoo hhaannddllee ooppttiioonnss Ultimate control over what should be done when (actually: each time) an option is encountered on the command line can be achieved by designating a reference to a subroutine (or an anonymous subroutine) as the option destination. When GGeettOOppttiioonnss(()) encounters the option, it will call the subroutine with two or three arguments. The first argument is the name of the option. (Actually, it is an object that stringifies to the name of the option.) For a scalar or array destination, the second argument is the value to be stored. For a hash destination, the second argument is the key to the hash, and the third argument the value to be stored. It is up to the subroutine to store the value, or do whatever it thinks is appropriate.

 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 "--verbose" and "--quiet" control the same variable $verbose, but
 with opposite values.

 If the subroutine needs to signal an error, it should call ddiiee(()) with the
 desired error message as its argument. GGeettOOppttiioonnss(()) will catch the ddiiee(()),
 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 "!" it
 is interpreted specially by GGeettOOppttiioonnss(()). There is currently one special
 command implemented: "die("!FINISH")" will cause GGeettOOppttiioonnss(()) to stop
 processing options, as if it encountered a double dash "--".

 Here is an example of how to access the option name and value from within
 a subroutine:

     GetOptions ('opt=i' => \&handler);
     sub handler {
         my ($opt_name, $opt_value) = @_;
         print("Option name is $opt_name and value is $opt_value\n");
     }

OOppttiioonnss wwiitthh mmuullttiippllee nnaammeess Often it is user friendly to supply alternate mnemonic names for options. For example “–height” could be an alternate name for “–length”. Alternate names can be included in the option specification, separated by vertical bar “|” characters. To implement the above example:

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

 The first name is called the _p_r_i_m_a_r_y name, the other names are called
 _a_l_i_a_s_e_s. When using a hash to store options, the key will always be the
 primary name.

 Multiple alternate names are possible.

CCaassee aanndd aabbbbrreevviiaattiioonnss Without additional configuration, GGeettOOppttiioonnss(()) 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 "--l" and "--L" for the length option, but requires
 a least "--hea" and "--hei" for the head and height options.

SSuummmmaarryy ooff OOppttiioonn SSppeecciiffiiccaattiioonnss 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

 !   The option does not take an argument and may be negated by prefixing
     it with "no" or "no-". E.g. "foo!" will allow "--foo" (a value of 1
     will be assigned) as well as "--nofoo" and "--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.

 +   The 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 increment the value three times,
     resulting in a value of 3 (provided it was 0 or undefined at first).

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

 = _t_y_p_e [ _d_e_s_t_t_y_p_e ] [ _r_e_p_e_a_t ]
     The option requires an argument of the given type. Supported types
     are:

     s   String. An arbitrary sequence of characters. It is valid for the
         argument to start with "-" or "--".

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

     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 ("0x" followed by '0' .. '9', 'a'
         .. 'f', case insensitive), or a binary string ("0b" followed by a
         series of '0' and '1').

     f   Real number. For example 3.14, "-6.23E24" and so on.

     The _d_e_s_t_t_y_p_e can be "@" or "%" 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 _r_e_p_e_a_t specifies the number of values this option takes per
     occurrence on the command line. It has the format "{" [ _m_i_n ] [ "," [
     _m_a_x ] ] "}".

     _m_i_n denotes the minimal number of arguments. It defaults to 1 for
     options with "=" and to 0 for options with ":", see below. Note that
     _m_i_n overrules the "=" / ":" semantics.

     _m_a_x denotes the maximum number of arguments. It must be at least _m_i_n.
     If _m_a_x is omitted, _b_u_t _t_h_e _c_o_m_m_a _i_s _n_o_t, there is no upper bound to
     the number of argument values taken.

 : _t_y_p_e [ _d_e_s_t_t_y_p_e ]
     Like "=", 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 "-" or "--", it will be
     considered an option on itself.

 : _n_u_m_b_e_r [ _d_e_s_t_t_y_p_e ]
     Like ":i", but if the value is omitted, the _n_u_m_b_e_r will be assigned.

 : + [ _d_e_s_t_t_y_p_e ]
     Like ":i", but if the value is omitted, the current value for the
     option will be incremented.

AAddvvaanncceedd PPoossssiibbiilliittiieess OObbjjeecctt oorriieenntteedd iinntteerrffaaccee Getopt::Long can be used in an object oriented way as well:

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

 Configuration options can be passed to the constructor:

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

CCaallllbbaacckk oobbjjeecctt In version 2.37 the first argument to the callback function was changed from string to object. This was done to make room for extensions and more detailed control. The object stringifies to the option name so this change should not introduce compatibility problems.

 The callback object has the following methods:

 name
     The name of the option, unabbreviated. For an option with multiple
     names it return the first (canonical) name.

 given
     The name of the option as actually used, unabbreveated.

TThhrreeaadd SSaaffeettyy Getopt::Long is thread safe when using ithreads as of Perl 5.8. It is _n_o_t thread safe when using the older (experimental and now obsolete) threads implementation that was added to Perl 5.005.

DDooccuummeennttaattiioonn aanndd hheellpp tteexxttss 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(-exitval => 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 Pod::Usage for details.

PPaarrssiinngg ooppttiioonnss ffrroomm aann aarrbbiittrraarryy aarrrraayy By default, GetOptions parses the options that are present in the global array @ARGV. A special entry “GetOptionsFromArray” can be used to parse options from an arbitrary array.

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

 When used like this, options and their possible values are removed from
 @myopts, the global @ARGV is not touched at all.

 The following two calls behave identically:

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

 This also means that a first argument hash reference now becomes the
 second argument:

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

PPaarrssiinngg ooppttiioonnss ffrroomm aann aarrbbiittrraarryy ssttrriinngg A special entry “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
 "Text::ParseWords::shellwords". As with "GetOptionsFromArray", the global
 @ARGV is not touched.

 It is possible that, upon completion, not all arguments in the string
 have been processed. "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 "GetOptionsFromString" was not called in
 list context, a message will be given and "GetOptionsFromString" will
 return failure.

 As with GetOptionsFromArray, a first argument hash reference now becomes
 the second argument. See the next section.

SSttoorriinngg ooppttiioonnss vvaalluueess iinn aa hhaasshh Sometimes, for example when there are a lot of options, having a separate variable for each of them can be cumbersome. GGeettOOppttiioonnss(()) supports, as an alternative mechanism, storing options values in a hash.

 To obtain this, a reference to a hash must be passed _a_s _t_h_e _f_i_r_s_t
 _a_r_g_u_m_e_n_t to GGeettOOppttiioonnss(()). 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, "exists($h{option})" (or
 ddeeffiinneedd(())) can be used to test if an option was used. The drawback is
 that warnings will be issued if the program runs under "use strict" and
 uses $h{option} without testing with eexxiissttss(()) or ddeeffiinneedd(()) 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 "@" or "%" 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 ... }

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

     -vax

 will set all three.

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

 The simplest style of bundling can be enabled with:

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

 Configured this way, single-character options can be bundled but long
 options (and any of their auto-abbreviated shortened forms) mmuusstt always
 start with a double dash "--" to avoid ambiguity. For example, when
 "vax", "a", "v" and "x" are all valid options,

     -vax

 will set "a", "v" and "x", but

     --vax

 will set "vax".

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

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

 Now, "-vax" will set the option "vax".

 In all of the above cases, option values may be inserted in the bundle.
 For example:

     -h24w80

 is equivalent to

     -h 24 -w 80

 A third style of bundling allows only values to be bundled with options.
 It can be enabled with:

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

 Now, "-h24" will set the option "h" to 24, but option bundles like "-vxa"
 and "-h24w80" are flagged as errors.

 Enabling "bundling_values" will disable the other two styles of bundling.

 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.

TThhee lloonneessoommee ddaasshh Normally, a lone dash “-” 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 @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 $stdio.

AArrgguummeenntt ccaallllbbaacckk A special option ’name’ “<>” can be used to designate a subroutine to handle non-option arguments. When GGeettOOppttiioonnss(()) 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 "process("arg1")" while $width is 80, "process("arg2")"
 while $width is 72, and "process("arg3")" while $width is 60.

 This feature requires configuration option ppeerrmmuuttee, see section
 "Configuring Getopt::Long".

CCoonnffiigguurriinngg GGeettoopptt::::LLoonngg Getopt::Long can be configured by calling subroutine GGeettoopptt::::LLoonngg::::CCoonnffiigguurree(()). This subroutine takes a list of quoted strings, each specifying a configuration option to be enabled, e.g. “ignore_case”. To disable, prefix with “no” or “no_”, e.g. “no_ignore_case”. Case does not matter. Multiple calls to CCoonnffiigguurree(()) are possible.

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

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

 The following options are available:

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

 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.

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

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

 gnu_compat  "gnu_compat" controls whether "--opt=" is allowed, and what
             it should do. Without "gnu_compat", "--opt=" gives an error.
             With "gnu_compat", "--opt=" will give option "opt" and empty
             value.  This is the way GNU ggeettoopptt__lloonngg(()) does it.

             Note that "--opt value" is still accepted, even though GNU
             ggeettoopptt__lloonngg(()) doesn't.

 gnu_getopt  This is a short way of setting "gnu_compat" "bundling"
             "permute" "no_getopt_compat". With "gnu_getopt", command line
             handling should be reasonably compatible with GNU
             ggeettoopptt__lloonngg(()).

 require_order
             Whether command line arguments are allowed to be mixed with
             options.  Default is disabled unless environment variable
             POSIXLY_CORRECT has been set, in which case "require_order"
             is enabled.

             See also "permute", which is the opposite of "require_order".

 permute     Whether command line arguments are allowed to be mixed with
             options.  Default is enabled unless environment variable
             POSIXLY_CORRECT has been set, in which case "permute" is
             disabled.  Note that "permute" is the opposite of
             "require_order".

             If "permute" is enabled, this means that

                 --foo arg1 --bar arg2 arg3

             is equivalent to

                 --foo --bar arg1 arg2 arg3

             If an argument callback routine is specified, @ARGV will
             always be empty upon successful return of GGeettOOppttiioonnss(()) since
             all options have been processed. The only exception is when
             "--" is used:

                 --foo arg1 --bar arg2 -- arg3

             This will call the callback routine for arg1 and arg2, and
             then terminate GGeettOOppttiioonnss(()) leaving "arg3" in @ARGV.

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

                 --foo arg1 --bar arg2 arg3

             is equivalent to

                 --foo -- arg1 --bar arg2 arg3

             If "pass_through" is also enabled, options processing will
             terminate at the first unrecognized option, or non-option,
             whichever comes first.

 bundling (default: disabled)
             Enabling this option will allow single-character options to
             be bundled. To distinguish bundles from long option names,
             long options (and any of their auto-abbreviated shortened
             forms) _m_u_s_t be introduced with "--" and bundles with "-".

             Note that, if you have options "a", "l" and "all", and
             auto_abbrev enabled, possible arguments and option settings
             are:

                 using argument               sets option(s)
                 ------------------------------------------
                 -a, --a                      a
                 -l, --l                      l
                 -al, -la, -ala, -all,...     a, l
                 --al, --all                  all

             The surprising part is that "--a" sets option "a" (due to
             auto completion), not "all".

             Note: disabling "bundling" also disables "bundling_override".

 bundling_override (default: disabled)
             If "bundling_override" is enabled, bundling is enabled as
             with "bundling" but now long option names override option
             bundles.

             Note: disabling "bundling_override" also disables "bundling".

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

 ignore_case  (default: enabled)
             If enabled, case is ignored when matching option names. If,
             however, bundling is enabled as well, single character
             options will be treated case-sensitive.

             With "ignore_case", option specifications for options that
             only differ in case, e.g., "foo" and "Foo", will be flagged
             as duplicates.

             Note: disabling "ignore_case" also disables
             "ignore_case_always".

 ignore_case_always (default: disabled)
             When bundling is in effect, case is ignored on single-
             character options also.

             Note: disabling "ignore_case_always" also disables
             "ignore_case".

 auto_version (default:disabled)
             Automatically provide support for the ----vveerrssiioonn option if the
             application did not specify a handler for this option itself.

             Getopt::Long will provide a standard version message that
             includes the program name, its version (if $main::VERSION is
             defined), and the versions of Getopt::Long and Perl. The
             message will be written to standard output and processing
             will terminate.

             "auto_version" will be enabled if the calling program
             explicitly specified a version number higher than 2.32 in the
             "use" or "require" statement.

 auto_help (default:disabled)
             Automatically provide support for the ----hheellpp and --?? options
             if the application did not specify a handler for this option
             itself.

             Getopt::Long will provide a help message using module
             Pod::Usage. The message, derived from the SYNOPSIS POD
             section, will be written to standard output and processing
             will terminate.

             "auto_help" will be enabled if the calling program explicitly
             specified a version number higher than 2.32 in the "use" or
             "require" statement.

 pass_through (default: disabled)
             With "pass_through" anything that is unknown, ambiguous or
             supplied with an invalid option will not be flagged as an
             error. Instead the unknown option(s) will be passed to the
             catchall "<>" if present, otherwise through to @ARGV. This
             makes it possible to write wrapper scripts that process only
             part of the user supplied command line arguments, and pass
             the remaining options to some other program.

             If "require_order" is enabled, options processing will
             terminate at the first unrecognized option, or non-option,
             whichever comes first and all remaining arguments are passed
             to @ARGV instead of the catchall "<>" if present.  However,
             if "permute" is enabled instead, results can become
             confusing.

             Note that the options terminator (default "--"), if present,
             will also be passed through in @ARGV.

 prefix      The string that starts options. If a constant string is not
             sufficient, see "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 allows the disambiguation of long and
             short prefixes. Default is "--".

             Typically you only need to set this if you are using
             nonstandard prefixes and want some or all of them to have the
             same semantics as '--' does under normal circumstances.

             For example, setting prefix_pattern to "--|-|\+|\/" and
             long_prefix_pattern to "--|\/" would add Win32 style argument
             handling.

 debug (default: disabled)
             Enable debugging output.

EExxppoorrttaabbllee MMeetthhooddss VersionMessage This subroutine provides a standard version message. Its argument can be:

     •   A string containing the text of a message to print _b_e_f_o_r_e
         printing the standard message.

     •   A numeric value corresponding to the desired exit status.

     •   A reference to a hash.

     If more than one argument is given then the entire argument list is
     assumed to be a hash.  If a hash is supplied (either as a reference
     or as a list) it should contain one or more elements with the
     following keys:

     "-message"
     "-msg"
         The text of a message to print immediately prior to printing the
         program's usage message.

     "-exitval"
         The desired exit status to pass to the eexxiitt(()) function.  This
         should be an integer, or else the string "NOEXIT" to indicate
         that control should simply be returned without terminating the
         invoking process.

     "-output"
         A reference to a filehandle, or the pathname of a file to which
         the usage message should be written. The default is "\*STDERR"
         unless the exit value is less than 2 (in which case the default
         is "\*STDOUT").

     You cannot tie this routine directly to an option, e.g.:

         GetOptions("version" => \&VersionMessage);

     Use this instead:

         GetOptions("version" => sub { VersionMessage() });

 HelpMessage
     This subroutine produces a standard help message, derived from the
     program's POD section SYNOPSIS using Pod::Usage. It takes the same
     arguments as VVeerrssiioonnMMeessssaaggee(()). In particular, you cannot tie it
     directly to an option, e.g.:

         GetOptions("help" => \&HelpMessage);

     Use this instead:

         GetOptions("help" => sub { HelpMessage() });

RReettuurrnn vvaalluueess aanndd EErrrroorrss Configuration errors and errors in the option definitions are signalled using ddiiee(()) and will terminate the calling program unless the call to GGeettoopptt::::LLoonngg::::GGeettOOppttiioonnss(()) was embedded in “eval { … }”, or ddiiee(()) was trapped using $SIG{DIE}.

 GetOptions returns true to indicate success.  It returns false when the
 function detected one or more errors during option parsing. These errors
 are signalled using wwaarrnn(()) and can be trapped with $SIG{__WARN__}.

LLeeggaaccyy The earliest development of “newgetopt.pl” started in 1990, with Perl version 4. As a result, its development, and the development of Getopt::Long, has gone through several stages. Since backward compatibility has always been extremely important, the current version of Getopt::Long still supports a lot of constructs that nowadays are no longer necessary or otherwise unwanted. This section describes briefly some of these ‘features’.

DDeeffaauulltt ddeessttiinnaattiioonnss When no destination is specified for an option, GetOptions will store the resultant value in a global variable named “opt_"_X_X_X, where _X_X_X is the primary name of this option. When a program executes under “use strict” (recommended), these variables must be pre-declared with oouurr(()) or “use vars”.

     our $opt_length = 0;
     GetOptions ('length=i');    # will store in $opt_length

 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);

AAlltteerrnnaattiivvee ooppttiioonn ssttaarrtteerrss A string of alternative option starter characters may be passed as the first argument (or the first argument after a leading hash reference argument).

     my $len = 0;
     GetOptions ('/', 'length=i' => $len);

 Now the command line may look like:

     /length 24 -- arg

 Note that to terminate options processing still requires a double dash
 "--".

 GGeettOOppttiioonnss(()) will not interpret a leading "<>" as option starters if the
 next argument is a reference. To force "<" and ">" as option starters,
 use "><". Confusing? Well, uussiinngg aa ssttaarrtteerr aarrgguummeenntt iiss ssttrroonnggllyy
 ddeepprreeccaatteedd anyway.

CCoonnffiigguurraattiioonn vvaarriiaabblleess 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 “Configure” routine that was introduced in version 2.17. Besides, it is much easier.

TTiippss aanndd TTeecchhnniiqquueess PPuusshhiinngg mmuullttiippllee vvaalluueess iinn aa hhaasshh ooppttiioonn Sometimes you want to combine the best of hashes and arrays. For example, the command line:

   --list add=first --list add=second --list add=third

 where each successive 'list add' option will push the value of add into
 array ref $list->{'add'}. The result would be like

   $list->{add} = [qw(first second third)];

 This can be accomplished with a destination routine:

   GetOptions('list=s%' =>
                sub { push(@{$list{$_[1]}}, $_[2]) });

TTrroouubblleesshhoooottiinngg GGeettOOppttiioonnss ddooeess nnoott rreettuurrnn aa ffaallssee rreessuulltt wwhheenn aann ooppttiioonn iiss nnoott ssuupppplliieedd That’s why they’re called ‘options’.

GGeettOOppttiioonnss ddooeess nnoott sspplliitt tthhee ccoommmmaanndd lliinnee ccoorrrreeccttllyy The command line is not split by GetOptions, but by the command line interpreter (CLI). On Unix, this is the shell. On Windows, it is COMMAND.COM or CMD.EXE. Other operating systems have other CLIs.

 It is important to know that these CLIs may behave different when the
 command line contains special characters, in particular quotes or
 backslashes. For example, with Unix shells you can use single quotes
 ("'") and double quotes (""") to group words together. The following
 alternatives are equivalent on Unix:

     "two words"
     'two words'
     two\ words

 In case of doubt, insert the following statement in front of your Perl
 program:

     print STDERR (join("|",@ARGV),"\n");

 to verify how your CLI passes the arguments to the program.

UUnnddeeffiinneedd ssuubbrroouuttiinnee &&mmaaiinn::::GGeettOOppttiioonnss ccaalllleedd Are you running Windows, and did you write

     use GetOpt::Long;

 (note the capital 'O')?

HHooww ddoo II ppuutt aa “”--??“” ooppttiioonn iinnttoo aa GGeettoopptt::::LLoonngg?? You can only obtain this using an alias, and Getopt::Long of at least version 2.13.

     use Getopt::Long;
     GetOptions ("help|?");    # -help and -? will both set $opt_help

 Other characters that can't appear in Perl identifiers are also supported
 in aliases with Getopt::Long of at version 2.39. Note that the characters
 "!", "|", "+", "=", and ":" can only appear as the first (or only)
 character of an alias.

 As of version 2.32 Getopt::Long provides auto-help, a quick and easy way
 to add the options --help and -? to your program, and handle them.

 See "auto_help" in section "Configuring Getopt::Long".

AAUUTTHHOORR #

 Johan Vromans <jvromans@squirrel.nl>

CCOOPPYYRRIIGGHHTT AANNDD DDIISSCCLLAAIIMMEERR #

 This program is Copyright 1990,2015 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.

 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.

perl v5.36.3 2023-02-15 Getopt::Long(3p)