---
name: "Getopt::Std"
section: "3p"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["openbsd"]
url: "https://new.carta.tech/Getopt::Std"
---

# Getopt::Std(3p)

Process single-character switches with switch clustering

## 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.