Computer Science
GETOPT(1) GETOPT(1)
NAME
getopt - parse command options (enhanced)
SYNOPSIS
getopt optstring parameters
getopt [options] [--] optstring parameters
getopt [options] -o|--options optstring [options] [--]
parameters
DESCRIPTION
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 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 occurence 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 parame-
ter shuffling and recognize optional arguments (see sec-
tion 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.
OPTIONS
-a, --alternative
Allow long options to start with a single `-'.
-h, --help
Output a small usage guide and exit succesfully. No
other output is generated.
-l, --longoptions longopts
The long (multi-character) options to be recog-
nized. 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 cummulative. 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) rou-
tines 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 options 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 influ-
ence the way options are parsed and output is gen-
erated (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 no -s
argument is found, the BASH conventions are used.
Valid arguments are currently `sh' `bash', `csh',
and `tcsh'.
-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).
-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.
-V, --version
Output version information and exit succesfully. No
other output is generated.
PARSING
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 corre-
sponds 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 parame-
ter 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 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 (ie. 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 abbrevia-
tion 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 inter-
preted 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
Output is generated for each element described in the pre-
vious 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 argu-
ment, 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) implemetations do not support optional argu-
ments.
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 gen-
erated 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 parame-
ter 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 occurences of
`-' and `+' are ignored).
QUOTING
In compatible mode, whitespace or 'special' characters in
arguments or non-option parameters are not handled cor-
rectly. As the output is fed to the shell script, the
script does not know how it is supposed to break the out-
put into separate parameters. To circumvent this problem,
this implementation offers quoting. The idea is that out-
put 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 SYNOP-
SIS 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.
SCANNING MODES
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 vari-
able 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
outputed 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.
COMPATIBILITY
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 (ie. all non-option parame-
ters are outputed 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.
RETURN CODES
getopt returns error code 0 for succesful 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.
EXAMPLES
Example scripts for (ba)sh and (t)csh are provided with
the getopt(1) distribution, and are optionally installed
in /usr/local/lib/getopt or /usr/lib/getopt.
ENVIRONMENT
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, regard-
less whether they start with a `-'.
GETOPT_COMPATIBLE
Forces getopt to use the first calling format as
specified in the SYNOPSIS.
BUGS
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
arguments that are empty as if they were not present.
AUTHOR
Frodo Looijaard <frodol@dds.nl>
SEE ALSO
getopt(3), bash(1), tcsh(1).
Linux May 31, 1997 1
Back to the index
