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GETOPT(1) User Commands GETOPT(1) NAME getopt - parse command options (enhanced) SYNOPSIS getopt optstring parameters getopt [options] [--] optstring parameters getopt [options] -o|--options optstring [options] [--] parameters DESCRIPTION getopt is used to break up (parse) options in command lines for easy pars- ing by shell procedures, and to check for valid options. It uses the GNU getopt(3) routines to do this. The parameters getopt is called with can be divided into two parts: options which modify the way getopt will do the parsing (the options and the opt- string in the SYNOPSIS), and the parameters which are to be parsed (parame- ters in the SYNOPSIS). The second part will start at the first non-option parameter that is not an option argument, or after the first occurrence of '--'. If no '-o' or '--options' option is found in the first part, the first parameter of the second part is used as the short options string. If the environment variable GETOPT_COMPATIBLE is set, or if the first para- meter is not an option (does not start with a '-', the first format in the SYNOPSIS), getopt will generate output that is compatible with that of other versions of getopt(1). It will still do parameter shuffling and rec- ognize optional arguments (see the COMPATIBILITY section for more informa- tion). Traditional implementations of getopt(1) are unable to cope with whitespace and other (shell-specific) special characters in arguments and non-option parameters. To solve this problem, this implementation can generate quoted output which must once again be interpreted by the shell (usually by using the eval command). This has the effect of preserving those characters, but you must call getopt in a way that is no longer compatible with other ver- sions (the second or third format in the SYNOPSIS). To determine whether this enhanced version of getopt(1) is installed, a special test option (-T) can be used. OPTIONS -a, --alternative Allow long options to start with a single '-'. -l, --longoptions longopts The long (multi-character) options to be recognized. More than one op- tion name may be specified at once, by separating the names with com- mas, whitespace (spaces, tabs, or newlines). This option may be given more than once, the longopts are cumulative. Each long option name in longopts may be followed by one colon to indicate it has a required ar- gument, and by two colons to indicate it has an optional argument. -n, --name progname The name that will be used by the getopt(3) routines when it reports errors. Note that errors of getopt(1) are still reported as coming from getopt. -o, --options shortopts The short (one-character) options to be recognized. If this option is not found, the first parameter of getopt that does not start with a '-' (and is not an option argument) is used as the short options string. Each short option character in shortopts may be followed by one colon to indicate it has a required argument, and by two colons to indicate it has an optional argument. The first character of shortopts may be '+' or '-' to influence the way options are parsed and output is gener- ated (see the SCANNING MODES section for details). -q, --quiet Disable error reporting by getopt(3). -Q, --quiet-output Do not generate normal output. Errors are still reported by getopt(3), unless you also use -q. -s, --shell shell Set quoting conventions to those of shell. If the -s option is not given, the BASH conventions are used. Valid arguments are currently 'sh', 'bash', 'csh', and 'tcsh'. -T, --test Test if your getopt(1) is this enhanced version or an old version. This generates no output, and sets the error status to 4. Other implementa- tions of getopt(1), and this version if the environment variable GETOPT_COMPATIBLE is set, will return '--' and error status 0. -u, --unquoted Do not quote the output. Note that whitespace and special (shell-depen- dent) characters can cause havoc in this mode (like they do with other getopt(1) implementations). -U, --unknown Leave unknown options as they are and suppress error messages from getopt(3). Since there is no way to know whether an unknown option re- quires an argument, a non-option argument that follows the unknown op- tion after a whitespace, is considered an option argument, therefore the argument will be left untouched and printed next to the respective unknown option. To prevent unexpected behavior, short options should be specified individually. -h, --help Display help text and exit. -V, --version Display version and exit. PARSING This section specifies the format of the second part of the parameters of getopt (the parameters in the SYNOPSIS). The next section (OUTPUT) de- scribes the output that is generated. These parameters were typically the parameters a shell function was called with. Care must be taken that each parameter the shell function was called with corresponds to exactly one pa- rameter in the parameter list of getopt (see the EXAMPLES). All parsing is done by the GNU getopt(3) routines. The parameters are parsed from left to right. Each parameter is classified as a short option, a long option, an argument to an option, or a non-option parameter. A simple short option is a '-' followed by a short option character, except for the ':', ';' and '?' characters, as these are reserved by getopt(3). If the option has a required argument, it may be written directly after the option character or as the next parameter (i.e., separated by whitespace on the command line). If the option has an optional argument, it must be writ- ten directly after the option character if present. It is possible to specify several short options after one '-', as long as all (except possibly the last) do not have required or optional arguments. A long option normally begins with '--' followed by the long option name. If the option has a required argument, it may be written directly after the long option name, separated by '=', or as the next argument (i.e., sepa- rated by whitespace on the command line). If the option has an optional ar- gument, it must be written directly after the long option name, separated by '=', if present (if you add the '=' but nothing behind it, it is inter- preted as if no argument was present; this is a slight bug, see the BUGS). Long options may be abbreviated, as long as the abbreviation is not ambigu- ous. Each parameter not starting with a '-', and not a required argument of a previous option, is a non-option parameter. Each parameter after a '--' pa- rameter is always interpreted as a non-option parameter. If the environment variable POSIXLY_CORRECT is set, or if the short option string started with a '+', all remaining parameters are interpreted as non-option parameters as soon as the first non-option parameter is found. OUTPUT Output is generated for each element described in the previous section. Output is done in the same order as the elements are specified in the in- put, except for non-option parameters. Output can be done in compatible (unquoted) mode, or in such way that whitespace and other special charac- ters within arguments and non-option parameters are preserved (see QUOT- ING). When the output is processed in the shell script, it will seem to be composed of distinct elements that can be processed one by one (by using the shift command in most shell languages). This is imperfect in unquoted mode, as elements can be split at unexpected places if they contain white- space or special characters. If there are problems parsing the parameters, for example because a re- quired argument is not found or an option is not recognized, an error will be reported on stderr, there will be no output for the offending element, and a non-zero error status is returned. For a short option, a single '-' and the option character are generated as one parameter. If the option has an argument, the next parameter will be the argument. If the option takes an optional argument, but none was found, the next parameter will be generated but be empty in quoting mode, but no second parameter will be generated in unquoted (compatible) mode. Note that many other getopt(1) implementations do not support optional arguments. If several short options were specified after a single '-', each will be present in the output as a separate parameter. For a long option, '--' and the full option name are generated as one para- meter. This is done regardless whether the option was abbreviated or speci- fied with a single '-' in the input. Arguments are handled as with short options. Normally, no non-option parameters output is generated until all options and their arguments have been generated. Then '--' is generated as a single parameter, and after it the non-option parameters in the order they were found, each as a separate parameter. Only if the first character of the short options string was a '-', non-option parameter output is generated at the place they are found in the input (this is not supported if the first format of the SYNOPSIS is used; in that case all preceding occurrences of '-' and '+' are ignored). QUOTING In compatibility mode, whitespace or 'special' characters in arguments or non-option parameters are not handled correctly. As the output is fed to the shell script, the script does not know how it is supposed to break the output into separate parameters. To circumvent this problem, this implemen- tation offers quoting. The idea is that output is generated with quotes around each parameter. When this output is once again fed to the shell (usually by a shell eval command), it is split correctly into separate pa- rameters. Quoting is not enabled if the environment variable GETOPT_COMPATIBLE is set, if the first form of the SYNOPSIS is used, or if the option '-u' is found. Different shells use different quoting conventions. You can use the '-s' option to select the shell you are using. The following shells are cur- rently supported: 'sh', 'bash', 'csh' and 'tcsh'. Actually, only two 'fla- vors' are distinguished: sh-like quoting conventions and csh-like quoting conventions. Chances are that if you use another shell script language, one of these flavors can still be used. SCANNING MODES The first character of the short options string may be a '-' or a '+' to indicate a special scanning mode. If the first calling form in the SYNOPSIS is used they are ignored; the environment variable POSIXLY_CORRECT is still examined, though. If the first character is '+', or if the environment variable POSIXLY_COR- RECT is set, parsing stops as soon as the first non-option parameter (i.e., a parameter that does not start with a '-') is found that is not an option argument. The remaining parameters are all interpreted as non-option para- meters. If the first character is a '-', non-option parameters are outputted at the place where they are found; in normal operation, they are all collected at the end of output after a '--' parameter has been generated. Note that this '--' parameter is still generated, but it will always be the last parameter in this mode. COMPATIBILITY This version of getopt(1) is written to be as compatible as possible to other versions. Usually you can just replace them with this version without any modifications, and with some advantages. If the first character of the first parameter of getopt is not a '-', getopt goes into compatibility mode. It will interpret its first parameter as the string of short options, and all other arguments will be parsed. It will still do parameter shuffling (i.e., all non-option parameters are out- put at the end), unless the environment variable POSIXLY_CORRECT is set, in which case, getopt will prepend a '+' before short options automatically. The environment variable GETOPT_COMPATIBLE forces getopt into compatibility mode. Setting both this environment variable and POSIXLY_CORRECT offers 100% compatibility for 'difficult' programs. Usually, though, neither is needed. In compatibility mode, leading '-' and '+' characters in the short options string are ignored. RETURN CODES getopt returns error code 0 for successful parsing, 1 if getopt(3) returns errors, 2 if it does not understand its own parameters, 3 if an internal error occurs like out-of-memory, and 4 if it is called with -T. EXAMPLES Example scripts for (ba)sh and (t)csh are provided with the getopt(1) dis- tribution, and are installed in /usr/share/doc/util-linux directory. ENVIRONMENT POSIXLY_CORRECT This environment variable is examined by the getopt(3) routines. If it is set, parsing stops as soon as a parameter is found that is not an option or an option argument. All remaining parameters are also inter- preted as non-option parameters, regardless whether they start with a '-'. GETOPT_COMPATIBLE Forces getopt to use the first calling format as specified in the SYN- OPSIS. BUGS getopt(3) can parse long options with optional arguments that are given an empty optional argument (but cannot do this for short options). This getopt(1) treats optional arguments that are empty as if they were not present. The syntax if you do not want any short option variables at all is not very intuitive (you have to set them explicitly to the empty string). AUTHOR Frodo Looijaard <frodo@frodo.looijaard.name> SEE ALSO bash(1), tcsh(1), getopt(3) REPORTING BUGS For bug reports, use the issue tracker <https://github.com/util-linux/util-linux/issues>. AVAILABILITY The getopt command is part of the util-linux package which can be down- loaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>. util-linux 2.42.2 2026-06-16 GETOPT(1)
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | PARSING | OUTPUT | QUOTING | SCANNING MODES | COMPATIBILITY | RETURN CODES | EXAMPLES | ENVIRONMENT | BUGS | AUTHOR | SEE ALSO | REPORTING BUGS | AVAILABILITY
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