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NAME

Getopt::Long - Extended processing of command line options
 

SYNOPSIS

  use Getopt::Long;
  my $data   = "file.dat";
  my $length = 24;
  my $verbose;
  $result = GetOptions ("length=i" => \$length,    # numeric
                        "file=s"   => \$data,      # string
                        "verbose"  => \$verbose);  # flag

DESCRIPTION

Command Line Options, an Introduction

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

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

    --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 to STDERR, and return a false result.  

A little bit less simple 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

    --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

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

    --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/srdlib" 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{,}" indicates one or more values; "foo:s{,}" indicates zero or more option values.  

Options with hash values

    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

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 "--".  

Options with multiple names

    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

    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

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

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

Configuration options can be passed to the constructor:

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

Thread Safety

Documentation and help texts

    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(-exitstatus => 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.  

Storing option 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

    -vax

would set all three.

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

The first level 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

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

    --vax

would set "vax".

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

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

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

When any level of bundling is enabled, option values may be inserted in the bundle. For example:

    -h24w80

is equivalent to

    -h 24 -w 80

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

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

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

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 "arg2" 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 long 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)

Options that are unknown, ambiguous or supplied with an invalid option value are passed through in @ARGV instead of being flagged as errors. 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. 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:

*

A string containing the text of a message to print before 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 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

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

Default destinations

    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

    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

Trouble Shooting

GetOptions does not return a false result when an option is not supplied

GetOptions does not split the command line correctly

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

    use GetOpt::Long;

(note the capital 'O')?  

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

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

AUTHOR

COPYRIGHT AND DISCLAIMER

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.

Index

NAME

SYNOPSIS

DESCRIPTION

Command Line Options, an Introduction

Getting Started with Getopt::Long

Simple options

A little bit less simple options

Mixing command line option with other arguments

Options with values

Options with multiple values

Options with hash values

User-defined subroutines to handle options

Options with multiple names

Case and abbreviations

Summary of Option Specifications

Advanced Possibilities

Object oriented interface

Thread Safety

Documentation and help texts

Storing option values in a hash

Bundling

The lonesome dash

Argument callback

Configuring Getopt::Long

Exportable Methods

Return values and Errors

Legacy

Default destinations

Alternative option starters

Configuration variables

Trouble Shooting

GetOptions does not return a false result when an option is not supplied

GetOptions does not split the command line correctly

Undefined subroutine &main::GetOptions called

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

AUTHOR

COPYRIGHT AND DISCLAIMER

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