Getopt::Std(3perl) Perl Programmers Reference Guide Getopt::Std(3perl)
NAME
Getopt::Std - Process single-character switches with switch clustering
SYNOPSIS
use Getopt::Std;
getopts('oif:'); # -o & -i are boolean flags, -f takes an argument
# Sets $opt_* global variables as a side effect
getopts('oif:', \my %opts); # Options as above, values in %opts
getopt('oDI'); # -o, -D & -I take arguments
# Sets $opt_* global variables as a side effect
getopt('oDI', \my %opts); # -o, -D & -I take arg, values in %opts
DESCRIPTION
The getopts() function processes single-character switches with switch
clustering. Pass one argument which is a string containing all switches
to be recognized. For each switch found, if an argument is expected and
provided, getopts() sets $opt_x (where "x" is the switch name) to the
value of the argument. If an argument is expected but none is provided,
$opt_x is set to an undefined value. If a switch does not take an
argument, $opt_x is set to 1.
Switches which take an argument don't care whether there is a space
between the switch and the argument. If unspecified switches are found
on the command-line, the user will be warned that an unknown option was
given.
The getopts() function returns true unless an invalid option was found.
The getopt() function is similar, but its argument is a string
containing all switches that take an argument. If no argument is
provided for a switch, say, "y", the corresponding $opt_y will be set to
an undefined value. Unspecified switches are silently accepted. Use of
getopt() is not recommended.
Note that, if your code is running under the recommended "use strict
vars" pragma, you will need to declare these package variables with
"our":
our($opt_x, $opt_y);
For those of you who don't like additional global variables being
created, getopt() and getopts() will also accept a hash reference as an
optional second argument. Hash keys will be "x" (where "x" is the
switch name) with key values the value of the argument or 1 if no
argument is specified.
To allow programs to process arguments that look like switches, but
aren't, both functions will stop processing switches when they see the
argument "--". The "--" will be removed from @ARGV.
--help" and "--version"
If "-" is not a recognized switch letter, getopts() supports arguments
"--help" and "--version". If main::HELP_MESSAGE() and/or
main::VERSION_MESSAGE() are defined, they are called; the arguments are
the output file handle, the name of option-processing package, its
version, and the switches string. If the subroutines are not defined,
an attempt is made to generate intelligent messages; for best results,
define $main::VERSION.
If embedded documentation (in pod format, see perlpod) is detected in
the script, "--help" will also show how to access the documentation.
Note that due to excessive paranoia, if
$Getopt::Std::STANDARD_HELP_VERSION isn't true (the default is false),
then the messages are printed on "STDERR", and the processing continues
after the messages are printed. This being the opposite of the
standard-conforming behaviour, it is strongly recommended to set
$Getopt::Std::STANDARD_HELP_VERSION to true.
One can change the output file handle of the messages by setting
$Getopt::Std::OUTPUT_HELP_VERSION. One can print the messages of
"--help" (without the "Usage:" line) and "--version" by calling
functions help_mess() and version_mess() with the switches string as an
argument.
perl v5.40.1 2026-08-30 Getopt::Std(3perl)
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