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




NAME

       Getopt::Long - Extended processing of command line options


SYNOPSIS

         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");


DESCRIPTION

       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:

           -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.


Getting Started with Getopt::Long

       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.

   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
       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.

   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 scalar reference as the destination:

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

       Used with the example above, @libfiles (or @$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
       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.

       = type [ desttype ] [ repeat ]
           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 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
           assigned.

       : + [ 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;

           __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.

   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
       hash.

       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
       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 ... }

   Bundling
       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 must 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.

   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
       example:

           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. Well,
       actually it is an object that stringifies to 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.

       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 getopt_long() does
                   it.

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

       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 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
                   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".

                   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".

       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 --version 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 --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".

       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.


Exportable Methods

       VersionMessage
           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:

           "-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 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.

           "-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 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
       $SIG{__WARN__}.


Legacy

       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'.

   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
       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
       "--".

       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]) });


Troubleshooting

   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
       program:

           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 as aliases with Getopt::Long of at least version 2.39.

       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".


AUTHOR

       Johan Vromans <jvromans@squirrel.nl>


COPYRIGHT AND DISCLAIMER

       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 v5.24.0                      2016-03-01                 Getopt::Long(3pm)

perl 5.24 - Generated Sun Nov 13 14:32:22 CST 2016
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