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 pro-
cedures, and to check for legal 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 parse (options and -o|--options 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 its first parameter is not an
option (does not start with a '-', this is 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 inter-
preted by the shell (usually by using the eval command). This has the effect of preserv-
ing 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.
Allow long options to start with a single '-'.
Output a small usage guide and exit successfully. 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 lon-
gopts 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).
Disable error reporting by getopt(3).
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 no -s argument is found, the BASH
conventions are used. Valid arguments are currently 'sh' 'bash', 'csh', and
Do not quote the output. Note that whitespace and special (shell-dependent) char-
acters can cause havoc in this mode (like they do with other getopt(1) implementa-
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.
Output version information and exit successfully. No other output is generated.
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 gen-
erated. 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 (ie. 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 pos-
sibly 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 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 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 parame-
ters. 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 unex-
pected 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 (compati-
ble) mode. Note that many other getopt(1) implementations do not support optional argu-
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 argu-
ments 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
In compatible mode, whitespace or 'special' characters in arguments or non-option parame-
ters 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 (usu-
ally 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 conven-
tions 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 spe-
cial 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 (ie. 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
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 (ie. all
non-option parameters are outputted at the end), unless the environment variable
POSIXLY_CORRECT is set.
The environment variable GETOPT_COMPATIBLE forces getopt into compatibility mode. Setting
both this environment variable and POSIXLY_CORRECT offers 100% compatibility for 'diffi-
cult' programs. Usually, though, neither is needed.
In compatibility mode, leading '-' and '+' characters in the short options string are
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 optionally installed in /usr/share/getopt/ or /usr/share/docs/ in util-linux subdirec-
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 '-'.
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 can not do this for short options). This getopt(1) treats optional argu-
ments 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 <email@example.com>
getopt(3), bash(1), tcsh(1).
The getopt command is part of the util-linux package and is available from Linux Kernel
util-linux June 2012 GETOPT(1)