Getopt::Std(3perl) Perl Programmers Reference Guide Getopt::Std(3perl)NAME
getopt, getopts - Process single-character switches with switch
getopt('oDI'); # -o, -D & -I take arg. Sets $opt_* as a side effect.
getopt('oDI', \%opts); # -o, -D & -I take arg. Values in %opts
getopts('oif:'); # -o & -i are boolean flags, -f takes an argument
# Sets $opt_* as a side effect.
getopts('oif:', \%opts); # options as above. Values in %opts
The getopt() function processes single-character switches with switch
clustering. Pass one argument which is a string containing all
switches that take an argument. For each switch found, sets $opt_x
(where x is the switch name) to the value of the argument if an
argument is expected, or 1 otherwise. Switches which take an argument
don't care whether there is a space between the switch and the
The getopts() function is similar, but you should pass to it the list
of all switches to be recognized. 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
Note that, if your code is running under the recommended "use strict
'vars'" pragma, you will need to declare these package variables with
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
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,
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
perl v5.18.2 2014-01-06 Getopt::Std(3perl)