getopt(1) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | PARSING | OUTPUT | QUOTING | SCANNING MODES | COMPATIBILITY | RETURN CODES | EXAMPLES | ENVIRONMENT | BUGS | AUTHOR | SEE ALSO | REPORTING BUGS | AVAILABILITY

GETOPT(1)                     User Commands                    GETOPT(1)

NAME         top

       getopt - parse command options (enhanced)

SYNOPSIS         top

       getopt optstring parameters getopt [options] [--] optstring
       parameters getopt [options] -o|--options optstring [options] [--]
       parameters

DESCRIPTION         top

       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         top

       -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         top

       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         top

       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         top

       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         top

       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         top

       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         top

       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         top

       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         top

       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         top

       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         top

       Frodo Looijaard <frodo@frodo.looijaard.name>

SEE ALSO         top

       bash(1), tcsh(1), getopt(3)

REPORTING BUGS         top

       For bug reports, use the issue tracker at
       https://github.com/karelzak/util-linux/issues.

AVAILABILITY         top

       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/>. This page
       is part of the util-linux (a random collection of Linux
       utilities) project. Information about the project can be found at
       ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have
       a bug report for this manual page, send it to
       util-linux@vger.kernel.org. This page was obtained from the
       project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
       2021-08-27. (At that time, the date of the most recent commit
       that was found in the repository was 2021-08-24.) If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page,
       or you have corrections or improvements to the information in
       this COLOPHON (which is not part of the original manual page),
       send a mail to man-pages@man7.org

util-linux 2.37.85-637cc       2021-06-17                      GETOPT(1)

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