getopt - Online in the Cloud

PROGRAM:

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 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.

OPTIONS

-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.

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. 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 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.

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.

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 optionally installed in /usr/share/getopt/ or /usr/share/doc/ in the util-linux
subdirectory.

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.

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