getopt - parse command options (enhanced)
getopt optstring parameters
] optstring parameters
is used to break up (parse
) options in command lines for
easy parsing by shell procedures, and to check for legal options. It uses the
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
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
' 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
is not an option (does not start with a '-
', the first
format in the SYNOPSIS
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
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
). To determine whether this enhanced version of
is installed, a special test option (-T
) can be used.
- -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
- -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.
This section specifies the format of the second part of the parameters of
in the SYNOPSIS
). The next section
) 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
). All parsing is done by the GNU getopt(3)
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
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
). Long options may be abbreviated, as long as the abbreviation is
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
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
) mode, or in such way that whitespace and other special
characters within arguments and non-option parameters are preserved (see
). 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
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
' and '+
' are ignored).
In compatible 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
command), it is split correctly into separate parameters.
Quoting is not enabled if the environment variable GETOPT_COMPATIBLE
set, if the first form of the SYNOPSIS
is used, or if the option
' 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
' 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
is used they are ignored; the environment variable
is still examined, though.
If the first character is '+
', or if the environment variable
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
' 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 '-
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
The environment variable GETOPT_COMPATIBLE
compatibility mode. Setting both this environment variable and
offers 100% compatibility for 'difficult' programs.
Usually, though, neither is needed.
In compatibility mode, leading '-
' and '+
' characters in the short
options string are ignored.
returns error code 0
for successful parsing, 1
returns errors, 2
if it does not understand its own
if an internal error occurs like out-of-memory, and
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/
in the util-linux subdirectory.
- 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
can parse long options with optional arguments that are given
an empty optional argument (but can not do this for short options). This
treats optional arguments that are empty as if they were not
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).
The getopt command is part of the util-linux package and is available from