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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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GETOPT(1) User Commands GETOPT(1)
getopt - parse command options (enhanced)
getopt optstring parameters
getopt [options] [--] optstring parameters
getopt [options] -o|--options optstring [options] [--] parameters
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.
-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.
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 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).
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.
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.
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.
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.
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.
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.
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).
Frodo Looijaard <frodo@frodo.looijaard.name>
bash(1), tcsh(1), getopt(3)
For bug reports, use the issue tracker at
https://github.com/util-linux/util-linux/issues.
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
2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-06-10.) 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 2.39.594-1e0ad 2023-07-19 GETOPT(1)
Pages that refer to this page: getopt(1), git-rev-parse(1), getopt(3)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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