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");
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 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.
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.
--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 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.
--size 24 -- --all
In this example, "--all" will not be treated as an option, but passed to the program unharmed, in @ARGV.
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 $tag = ''; # option variable with default value
GetOptions ('tag=s' => \$tag);
In the option specification, the option name is followed by an equals sign "=" and the letter "s". The equals sign indicates that this option requires a value. The letter "s" indicates that this value is an arbitrary string. Other possible value types are "i" for integer values, and "f" for floating point values. Using a colon ":" instead of the equals sign indicates that the option value is optional. In this case, if no suitable value is supplied, string valued options get an empty string '' assigned, while numeric options are set to 0.
--library lib/stdlib --library lib/extlib
To accomplish this behaviour, simply specify an array reference as the destination for the option:
GetOptions ("library=s" => \@libfiles);
Alternatively, you can specify that the option can have multiple values by adding a ``@'', and pass a reference to a scalar as the destination:
GetOptions ("library=s@" => \$libfiles);
Used with the example above, @libfiles c.q. @$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.
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.
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");
}
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.
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.
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
Using negation on a single letter option when bundling is in effect is pointless and will result in a warning.
The "+" specifier is ignored if the option destination is not a scalar.
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.
Note that if a string argument starts with "-" or "--", it will be considered an option on itself.
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...];
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
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, ... );
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.
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 ... }
-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.
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.
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''.
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:
Note that "--opt value" is still accepted, even though GNU getopt_long() doesn't.
See also "permute", which 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.
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".
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.
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".
Note: disabling "ignore_case_always" also disables "ignore_case".
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.
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.
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.
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.
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:
You cannot tie this routine directly to an option, e.g.:
GetOptions("version" => \&VersionMessage);
Use this instead:
GetOptions("version" => sub { VersionMessage() });
GetOptions("help" => \&HelpMessage);
Use this instead:
GetOptions("help" => sub { HelpMessage() });
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__}.
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);
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.
--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]) });
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.
use GetOpt::Long;
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''.
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.