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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | PARSING | OUTPUT | QUOTING | SCANNING MODES | COMPATIBILITY | RETURN CODES | EXAMPLES | ENVIRONMENT | BUGS | AUTHOR | SEE ALSO | AVAILABILITY | COLOPHON |
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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 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 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 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
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 '-'.
-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 '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).
-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 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 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 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.
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 optionally installed in /usr/share/getopt/ or
/usr/share/doc/ in the util-linux subdirectory.
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)
The getopt command is part of the util-linux package and is available
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
2018-02-02. (At that time, the date of the most recent commit that
was found in the repository was 2018-02-01.) 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 December 2014 GETOPT(1)
Pages that refer to this page: getopt(1), git-rev-parse(1), groffer(1), getopt(3)
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