|
Getopt::Long - Extended processing of command line options
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
|
|
The Getopt::Long module implements an extended getopt function called GetOptions(). 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 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.
Usually, these single-character options can be bundled:
Options can have values, the value is placed after the option character. Sometimes with
whitespace in between, sometimes not:
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
or
The + form is now obsolete and strongly deprecated.
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, hence the
name Getopt::Long. This module also supports single-character options and bundling. In this
case, the options are restricted to alphabetic characters only, and the characters ?
and -.
To use Getopt::Long from a Perl program, you must include the following line in your Perl
program:
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.
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 to STDERR, and return a false result.
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.
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:
In this example, --all will not be treated as an option, but passed to
the program unharmed, in @ARGV.
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 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:
my @libfiles = ();
GetOptions ("library=s" => \@libfiles);
|
|
Used with the example above, @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
acceptible 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:
my @libfiles = ();
GetOptions ("library=s" => \@libfiles);
@libfiles = split(/,/,join(',',@libfiles));
|
|
Of course, it is important to choose the right separator string for each purpose.
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.
my %defines = ();
GetOptions ("define=s" => \%defines);
|
|
When used with command line options:
--define os=linux --define vendor=redhat
|
|
the hash %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 acceptible
values. The keys are always taken to be strings.
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. For a scalar or array destination, the second argument is the value to be stored. For
a hash destination, the second arguments 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 exclamantion 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 --.
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.
Multiple alternate names are possible.
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.
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, i.e. prefixed by
"no". E.g. "foo!" will allow --foo (a value
of 1 will be assigned) and --nofoo (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 ]
-
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.
- : 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.
Getopt::Long can be used in an object oriented way as well:
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...];
|
|
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.
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(-exitstatus => 0, -verbose => 2) if $man;
__END__
=head1 NAME
sample - Using GetOpt::Long and Pod::Usage
=head1 SYNOPSIS
sample [options] [file ...]
Options:
-help brief help message
-man full documentation
=head1 OPTIONS
=over 8
=item B<-help>
Print a brief help message and exits.
=item B<-man>
Prints the manual page and exits.
=back
=head1 DESCRIPTION
B<This program> will read the given input file(s) and do someting
useful with the contents thereof.
=cut
|
|
See Pod::Usage for details.
Sometimes, for example when there are a lot of options, having a separate variable for each
of them can be cumbersome. GetOptions() supports, as an alternative mechanism, storing options
in a hash.
To obtain this, a reference to a hash must be passed as the first argument to
GetOptions(). For each option that is specified on the command line, the option value will be
stored in the hash with the option name as key. Options that are not actually used on the
command line will not be put in the hash, on other words, exists($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 ... }
|
|
With bundling it is possible to set several single-character options at once. For example
if a, v and x are all valid options,
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 abiguity. For example, when vax,
a, v and x are all valid options,
would set a, v and x, but
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:
is equivalent to
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.
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.
A special option 'name' <> can be used to designate a subroutine to
handle non-option arguments. When GetOptions() encounters an argument that does not look like
an option, it will immediately call this subroutine and passes it one parameter: the argument
name.
For example:
my $width = 80;
sub process { ... }
GetOptions ('width=i' => \$width, '<>' => \&process);
|
|
When applied to the following command line:
arg1 --width=72 arg2 --width=60 arg3
|
|
This will call process("arg1") while $width is 80,
process("arg2") while $width is 72, and process("arg3")
while $width is 60.
This feature requires configuration option permute, see section Configuring Getopt::Long.
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 succesful 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 suprising 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.
- 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.
- 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 (--|-).
- debug (default: disabled)
- Enable debugging output.
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__}.
Errors that can't happen are signalled using Carp::croak().
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'.
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 progam 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);
|
|
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:
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.
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.
This warning is issued when the '!' modifier is applied to a short (one-character) option
and bundling is in effect. E.g.,
Getopt::Long::Configure("bundling");
GetOptions("foo|f!" => \$foo);
|
|
Note that older Getopt::Long versions did not issue a warning, because the '!' modifier was
applied to the first name only. This bug was fixed in 2.22.
Solution: separate the long and short names and apply the '!' to the long names only, e.g.,
GetOptions("foo!" => \$foo, "f" => \$foo);
|
|
That's why they're called 'options'.
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.
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
|
|
Johan Vromans <jvromans@squirrel.nl>
This program is Copyright 2002,1990 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.
|
|
