Manual: getopt

GETOPT(1) User Commands 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
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 getopt(1). It will still do parameter shuffling and recognize optional arguments (see the COMPATIBILITY 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 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 '-'.

-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 the SCANNING MODES section 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).

-h, --help
Display help text and exit.

-V, --version
Display version and exit.

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 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, except for the ':', ';' and '?' characters, as
these are reserved by getopt(3). 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
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).

QUOTING
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.

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 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.

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 (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.

RETURN CODES
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.

EXAMPLES
Example scripts for (ba)sh and (t)csh are provided with the getopt(1) distribution, and are installed in
/usr/share/doc/util-linux/examples/ directory.

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, regardless 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 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).

AUTHOR
Frodo Looijaard

Manual: getopt

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