getopt - phpMan

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) rou-
tines 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 SYNOP-
SIS), 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 its first parameter is
not an option (does not start with a ‘-’, this is the first format in the SYNOP-
SIS), 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
Output a small usage guide and exit succesfully. No other output is gener-
ated.

-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 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 gen-
erates 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 gener-
ated.

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 (ie. separated by whitespace on the command line). If the
option has an optional argument, it must be written directly after the option char-
acter 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 abbre-
viation 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 argu-
ment 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) implemeta-
tions 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 sin-
gle ‘-’ 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 parame-
ters. 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 cor-
rectly 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 (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 ver-
sions. Usually you can just replace them with this version without any modifica-
tions, 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 parameters are outputed at the end), unless the envi-
ronment 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% compatibil-
ity 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, 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 can not 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 intu-
itive (you have to set them explicitely to the empty string).

AUTHOR
Frodo Looijaard <frodol AT dds.nl>