parse command options (enhanced)
getopt [options] [−−] optstring
optstring [options] [−−]
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 GNU getopt(3)
routines to do this.
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
’−−options’ option is found
in the first part, the first parameter of the second part is
used as the short options string.
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
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
Allow long options to start
with a single ’−’.
Display help text and exit. No
other output is generated.
(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.
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
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
Do not generate normal output.
Errors are still reported by getopt(3), unless you
also use −q.
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
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
Do not quote the output. Note
that whitespace and special (shell-dependent) characters can
cause havoc in this mode (like they do with other
Display version information and
exit. No other output is generated.
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)
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
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.
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.
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.
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.
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).
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
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.
shells use different quoting conventions. You can use the
’−s’ option to select the shell you
are using. The following shells are currently supported:
’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.
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
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
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
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
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.
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
compatibility mode, leading ’−’ and
’+’ characters in the short options
string are ignored.
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.
for (ba)sh and (t)csh are provided with the getopt(1)
distribution, and are optionally installed in
/usr/share/getopt/ or /usr/share/doc/ in the
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 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
command is part of the util-linux package and is available