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 . It will still
do parameter shuffling and recognize optional arguments (see the
COMPATIBILITY section for more information).
Traditional implementations of 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
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
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
-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 is this enhanced
version or an old version. This generates no output, and sets the error status
to 4. Other implementations of , 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 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 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 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
distribution, and are installed in
/usr/share/doc/util-linux/examples/
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
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 <
[email protected]>Looijaard
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/>.