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

       Getopt::Long - Extended processing of command line options

	 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");

       The Getopt::Long	module implements an extended getopt function called
       GetOptions(). 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.

Command	Line Options, an Introduction
       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 options 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:


       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

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

Getting	Started	with Getopt::Long
       Getopt::Long is the Perl5 successor of "". 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.

   Simple options
       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 GetOptions()	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 enabling
       the option.

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

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

   A little bit	less simple options
       Getopt::Long supports two useful	variants of simple options: negatable
       options and incremental 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

	   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.

   Mixing command line option with other arguments
       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 not be treated as an option, but passed
       to the program unharmed,	in @ARGV.

   Options with	values
       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.

   Options with	multiple values
       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 split()
       and join() 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.

   Options with	hash values
       If the option destination is a reference	to a hash, the option will
       take, as	value, strings of the form key"="value.	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.

   User-defined	subroutines to handle options
       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 GetOptions() 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 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	"!"
       it is interpreted specially by GetOptions(). There is currently one
       special command implemented: "die("!FINISH")" will cause	GetOptions()
       to stop processing options, as if it encountered	a double dash "--".

       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.

       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");

   Options with	multiple names
       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 primary name, the other names are called
       aliases.	When using a hash to store options, the	key will always	be the
       primary name.

       Multiple	alternate names	are possible.

   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 "--l" and "--L" for	the length option, but
       requires	a least	"--hea"	and "--hei" for	the head and height options.

   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

	   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

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

       = type [	desttype ] [ repeat ]
	   The option requires an argument of the given	type. Supported	types

	   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 desttype	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 repeat specifies	the number of values this option takes per
	   occurrence on the command line. It has the format "{" [ min ] [ ","
	   [ max ] ] "}".

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

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

       : type [	desttype ]
	   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.

       : number	[ desttype ]
	   Like	":i", but if the value is omitted, the number will be

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

Advanced Possibilities
   Object oriented interface
       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...];

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

   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(-exitval => 0, -verbose =>	2) if $man;


	   =head1 NAME

	   sample - Using Getopt::Long and Pod::Usage

	   =head1 SYNOPSIS

	   sample [options] [file ...]

	      -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.


	   =head1 DESCRIPTION

	   B<This program> will	read the given input file(s) and do something
	   useful with the contents thereof.


       See Pod::Usage for details.

   Parsing options from	an arbitrary array
       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, ... );

   Parsing options from	an arbitrary string
       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.

   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

       To obtain this, a reference to a	hash must be passed 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, "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 "use strict"
       and uses	$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 "@"	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

	   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	... }

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


       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 must always start with a	double dash "--" to avoid ambiguity.
       For example, when "vax",	"a", "v" and "x" are all valid options,


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


       will set	"vax".

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

	   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:


       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

       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.

   The lonesome	dash
       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

	   GetOptions ('' => \$stdio);

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

   Argument callback
       A special option	'name' "<>" 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 "process("arg1")"	while $width is	80, "process("arg2")"
       while $width is 72, and "process("arg3")" while $width is 60.

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

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.
       "ignore_case", or disabled, e.g.	"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	"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.

		   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.

		   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 getopt_long() does

		   Note	that "--opt value" is still accepted, even though GNU
		   getopt_long() 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

		   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

       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

		   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 GetOptions()
		   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 GetOptions() 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	must 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

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

		   Note: disabling "bundling_override" also disables

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

		   Note: disabling "ignore_case_always"	also disables

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

		   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 --help	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".

		   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 "--|-".

		   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.

Exportable Methods
	   This	subroutine provides a standard version message.	Its argument
	   can be:

	   o   A string	containing the text of a message to print before
	       printing	the standard message.

	   o   A numeric value corresponding to	the desired exit status.

	   o   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:

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

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

	       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() });

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

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

	   Use this instead:

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

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__}.

       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 warn() and can be trapped with

       The earliest development	of "" 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'.

   Default destinations
       When no destination is specified	for an option, GetOptions will store
       the resultant value in a	global variable	named "opt_"XXX, where XXX is
       the primary name	of this	option.	When a program executes	under "use
       strict" (recommended), these variables must be pre-declared with	our()
       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);

   Alternative option starters
       A string	of alternative option starter characters may be	passed as the
       first argument (or the first argument after a leading hash reference

	   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

       GetOptions() will not interpret a leading "<>" as option	starters if
       the next	argument is a reference. To force "<" and ">" as option
       starters, use "><". Confusing? Well, using a starter argument is
       strongly	deprecated anyway.

   Configuration variables
       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.

Tips and Techniques
   Pushing multiple values in a	hash option
       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]) });

   GetOptions does not return a	false result when an option is not supplied
       That's why they're called 'options'.

   GetOptions does not split the command line correctly
       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

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

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

   Undefined subroutine	&main::GetOptions called
       Are you running Windows,	and did	you write

	   use GetOpt::Long;

       (note the capital 'O')?

   How do I put	a "-?" option into a Getopt::Long?
       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".

       Johan Vromans <>

       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
       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,

perl v5.32.0			  2020-06-14		       Getopt::Long(3)

NAME | SYNOPSIS | DESCRIPTION | Command Line Options, an Introduction | Getting Started with Getopt::Long | Advanced Possibilities | Configuring Getopt::Long | Exportable Methods | Return values and Errors | Legacy | Tips and Techniques | Troubleshooting | AUTHOR | COPYRIGHT AND DISCLAIMER

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