getopt

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
       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 section COMPATIBILITY 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 '-'.

       -h, --help
           Display help text and exit. No other output is generated.

       -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 section SCANNING MODES 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).

       -V, --version
           Display version information and exit. No other output is generated.

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 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/karelzak/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/>.



util-linux 2.37.2                  2021-06-02                          GETOPT(1)