- NAME
- SYNOPSIS
- DESCRIPTION
- --help and --version

# NAME

getopt, getopts - Process single-character switches with switch clustering

# SYNOPSIS

        use Getopt::Std;

        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
        getopt('oDI');    # -o, -D & -I take arg.
                          # Sets $opt_* as a side effect.
        getopt('oDI', \%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 `getopts()` 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.