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 parsing 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 optstring in the SYNOPSIS), and
       the parameters which are to be parsed (parameters 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 parameter 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 recognize optional arguments (see the COMPATIBILITY section for
       more information).

       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 versions (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 option name may be
           specified at once, by separating the names with commas. 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 argument, 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 generated (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 implementations 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-dependent) characters
           can cause havoc in this mode (like they do with other getopt(1) implementations).

       -h, --help
           Display help text and exit.

       -V, --version
           Print 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) describes 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 parameter 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. 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 written 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., separated by whitespace on the command line). If
       the option has an optional argument, it must be written directly after the long option
       name, separated by '=', if present (if you add the '=' but nothing behind it, it is
       interpreted 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 ambiguous.

       Each parameter not starting with a '-', and not a required argument of a previous option,
       is a non-option parameter. Each parameter after a '--' parameter 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 input, except for non-option
       parameters. Output can be done in compatible (unquoted) mode, or in such way that
       whitespace and other special characters within arguments and non-option parameters are
       preserved (see QUOTING). 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 whitespace or special characters.

       If there are problems parsing the parameters, for example because a required 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 parameter. This is
       done regardless whether the option was abbreviated or specified 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 implementation 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 parameters.

       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 currently supported: 'sh', 'bash', 'csh'
       and 'tcsh'. Actually, only two 'flavors' 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_CORRECT 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 parameters.

       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 output 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) distribution, and
       are installed in /usr/share/doc/util-linux/examples/ 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 interpreted as non-option parameters, regardless whether
           they start with a '-'.

       GETOPT_COMPATIBLE
           Forces getopt to use the first calling format as specified in the SYNOPSIS.

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 at https://github.com/util-linux/util-linux/issues.

AVAILABILITY

       The getopt command is part of the util-linux package which can be downloaded from Linux
       Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.