getopt/trunk/getopt.1

.TH GETOPT "1" "June 2012" "Linux" "User Commands"
.SH NAME
getopt \- parse command options (enhanced)
.SH SYNOPSIS
.BI getopt
.I optstring parameters
.br
.B getopt
.RI [ options ]
.RB [ \-\- ]
.I optstring parameters
.br
.B getopt
.RI [ options ]
.BR \-o | \-\-options
.I optstring
.RI [ options ]
.RB [ \-\- ]
.I parameters
.SH DESCRIPTION
.B getopt
is used to break up
.RI ( parse )
options in command lines for easy parsing by shell procedures, and to
check for legal options.  It uses the
.SM GNU
.BR getopt (3)
routines to do this.
.PP
The parameters
.B getopt
is called with can be divided into two parts: options which modify
the way
.B getopt
will do the parsing
.RI "(the " options
and the
.I optstring
in the
.BR SYNOPSIS ),
and the parameters which are to be parsed
.RI ( parameters
in the
.BR SYNOPSIS ).
The second part will start at the first non\-option parameter that is
not an option argument, or after the first occurrence of
.RB ' \-\- '.
If no
.RB ' \-o '
or
.RB ' \-\-options '
option is found in the first part, the first parameter of the second
part is used as the short options string.
.PP
If the environment variable
.B GETOPT_COMPATIBLE
is set, or if the first \fIparameter\fR is not an option (does not start
with a
.RB ' \- ',
the first format in the
.BR SYNOPSIS ),
.B getopt
will generate output that is compatible with that of other versions of
.BR getopt (1).
It will still do parameter shuffling and recognize optional arguments
(see section
.B COMPATIBILITY
for more information).
.PP
Traditional implementations of
.BR 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
.B eval
command).  This has the effect of preserving those characters, but
you must call
.B getopt
in a way that is no longer compatible with other versions (the second
or third format in the
.BR SYNOPSIS ).
To determine whether this enhanced version of
.BR getopt (1)
is installed, a special test option
.RB ( \-T )
can be used.
.SH OPTIONS
.TP
.BR \-a , " \-\-alternative"
Allow long options to start with a single
.RB ' \- '.
.TP
.BR \-h , " \-\-help"
Display help text and exit.  No other output is generated.
.TP
.BR \-l , " \-\-longoptions \fIlongopts\fP"
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
.I longopts
are cumulative.  Each long option name in
.I 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.
.TP
.BR \-n , " \-\-name \fIprogname\fP"
The name that will be used by the
.BR getopt (3)
routines when it reports errors.  Note that errors of
.BR getopt (1)
are still reported as coming from getopt.
.TP
.BR \-o , " \-\-options \fIshortopts\fP"
The short (one\-character) options to be recognized.  If this option
is not found, the first parameter of
.B getopt
that does not start with a
.RB ' \- '
(and is not an option argument) is used as the short options string.
Each short option character in
.I 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
.RB ' + '
or
.RB ' \- '
to influence the way options are parsed and output is generated (see
section
.B SCANNING MODES
for details).
.TP
.BR \-q , " \-\-quiet"
Disable error reporting by getopt(3).
.TP
.BR  \-Q , " \-\-quiet\-output"
Do not generate normal output.  Errors are still reported by
.BR getopt (3),
unless you also use
.BR \-q .
.TP
.BR \-s , " \-\-shell \fIshell\fP"
Set quoting conventions to those of \fIshell\fR.
If the \fB\-s\fR option is not given, the
.SM BASH
conventions are used.  Valid arguments are currently
.RB ' sh '
.RB ' bash ',
.RB ' csh ',
and
.RB ' tcsh '.
.TP
.BR \-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
.BR getopt (1)
implementations).
.TP
.BR \-T , " \-\-test"
Test if your
.BR getopt (1)
is this enhanced version or an old version.  This generates no
output, and sets the error status to 4.  Other implementations of
.BR getopt (1),
and this version if the environment variable
.B GETOPT_COMPATIBLE
is set, will return
.RB ' \-\- '
and error status 0.
.TP
.BR \-V , " \-\-version"
Display version information and exit.  No other output is generated.
.SH PARSING
This section specifies the format of the second part of the
parameters of
.B getopt
(the
.I parameters
in the
.BR SYNOPSIS ).
The next section
.RB ( 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
.B getopt
(see the
.BR EXAMPLES ).
All parsing is done by the GNU
.BR getopt (3)
routines.
.PP
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.
.PP
A simple short option is a
.RB ' \- '
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.
.PP
It is possible to specify several short options after one
.RB ' \- ',
as long as all (except possibly the last) do not have required or
optional arguments.
.PP
A long option normally begins with
.RB ' \-\- '
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
.RB ' = ',
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
.RB ' = ',
if present (if you add the
.RB ' = '
but nothing behind it, it is interpreted as if no argument was
present; this is a slight bug, see the
.BR BUGS ).
Long options may be abbreviated, as long as the abbreviation is not
ambiguous.
.PP
Each parameter not starting with a
.RB ' \- ',
and not a required argument of a previous option, is a non\-option
parameter.  Each parameter after a
.RB ' \-\- '
parameter is always interpreted as a non\-option parameter.  If the
environment variable
.B POSIXLY_CORRECT
is set, or if the short option string started with a
.RB ' + ',
all remaining parameters are interpreted as non\-option parameters as
soon as the first non\-option parameter is found.
.SH 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
.I compatible
.RI ( unquoted )
mode, or in such way that whitespace and other special characters
within arguments and non\-option parameters are preserved (see
.BR 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.
.PP
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.
.PP
For a short option, a single
.RB ' \- '
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
.BR getopt (1)
implementations do not support optional arguments.
.PP
If several short options were specified after a single
.RB ' \- ',
each will be present in the output as a separate parameter.
.PP
For a long option,
.RB ' \-\- '
and the full option name are generated as one parameter.  This is
done regardless whether the option was abbreviated or specified with
a single
.RB ' \- '
in the input.  Arguments are handled as with short options.
.PP
Normally, no non\-option parameters output is generated until all
options and their arguments have been generated.  Then
.RB ' \-\- '
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
.RB ' \- ',
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
.B SYNOPSIS
is used; in that case all preceding occurrences of
.RB ' \- '
and
.RB ' + '
are ignored).
.SH 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
.B eval
command), it is split correctly into separate parameters.
.PP
Quoting is not enabled if the environment variable
.B GETOPT_COMPATIBLE
is set, if the first form of the
.B SYNOPSIS
is used, or if the option
.RB ' \-u '
is found.
.PP
Different shells use different quoting conventions.  You can use the
.RB ' \-s '
option to select the shell you are using.  The following shells are
currently supported:
.RB ' sh ',
.RB ' bash ',
.RB ' csh '
and
.RB ' 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.
.SH "SCANNING MODES"
The first character of the short options string may be a
.RB ' \- '
or a
.RB ' + '
to indicate a special scanning mode.  If the first calling form in
the
.B SYNOPSIS
is used they are ignored; the environment variable
.B POSIXLY_CORRECT
is still examined, though.
.PP
If the first character is
.RB ' + ',
or if the environment variable
.B POSIXLY_CORRECT
is set, parsing stops as soon as the first non\-option parameter
(i.e. a parameter that does not start with a
.RB ' \- ')
is found that is not an option argument.  The remaining parameters
are all interpreted as non\-option parameters.
.PP
If the first character is a
.RB ' \- ',
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
.RB ' \-\- '
parameter has been generated.  Note that this
.RB ' \-\- '
parameter is still generated, but it will always be the last
parameter in this mode.
.SH COMPATIBILITY
This version of
.BR 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.
.PP
If the first character of the first parameter of getopt is not a
.RB ' \- ',
.B 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
.B POSIXLY_CORRECT
is set.
.PP
The environment variable
.B GETOPT_COMPATIBLE
forces
.B getopt
into compatibility mode.  Setting both this environment variable and
.B POSIXLY_CORRECT
offers 100% compatibility for 'difficult' programs.  Usually, though,
neither is needed.
.PP
In compatibility mode, leading
.RB ' \- '
and
.RB ' + '
characters in the short options string are ignored.
.SH RETURN CODES
.B getopt
returns error code
.B 0
for successful parsing,
.B 1
if
.BR getopt (3)
returns errors,
.B 2
if it does not understand its own parameters,
.B 3
if an internal error occurs like out\-of\-memory, and
.B 4
if it is called with
.BR \-T .
.SH EXAMPLES
Example scripts for (ba)sh and (t)csh are provided with the
.BR getopt (1)
distribution, and are optionally installed in
.BR /usr/local/share/getopt/
or
.BR /usr/share/getopt/ .
.SH ENVIRONMENT
.IP POSIXLY_CORRECT
This environment variable is examined by the
.BR 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
.RB ' \- '.
.IP GETOPT_COMPATIBLE
Forces
.B getopt
to use the first calling format as specified in the
.BR SYNOPSIS .
.SH BUGS
.BR 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
.BR getopt (1)
treats optional arguments that are empty as if they were not present.
.PP
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).
.SH AUTHOR
.MT frodo@frodo.looijaard.name
Frodo Looijaard
.ME
.SH "SEE ALSO"
.BR getopt (3),
.BR bash (1),
.BR tcsh (1).
.SH AVAILABILITY
You can download the latest getopt from
.UR http://frodo.looijaard.name/project/getopt
the author's home page
.UE .
It is also part of the util-linux package which is available from
.UR ftp://\:ftp.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
Linux Kernel Archive
.UE .
1	.TH GETOPT "1" "June 2012" "Linux" "User Commands"
2	.SH NAME
3	getopt \- parse command options (enhanced)
4	.SH SYNOPSIS
5	.BI getopt
6	.I optstring parameters
7	.br
8	.B getopt
9	.RI [ options ]
10	.RB [ \-\- ]
11	.I optstring parameters
12	.br
13	.B getopt
14	.RI [ options ]
15	.BR \-o \| \-\-options
16	.I optstring
17	.RI [ options ]
18	.RB [ \-\- ]
19	.I parameters
20	.SH DESCRIPTION
21	.B getopt
22	is used to break up
23	.RI ( parse )
24	options in command lines for easy parsing by shell procedures, and to
25	check for legal options. It uses the
26	.SM GNU
27	.BR getopt (3)
28	routines to do this.
29	.PP
30	The parameters
31	.B getopt
32	is called with can be divided into two parts: options which modify
33	the way
34	.B getopt
35	will do the parsing
36	.RI "(the " options
37	and the
38	.I optstring
39	in the
40	.BR SYNOPSIS ),
41	and the parameters which are to be parsed
42	.RI ( parameters
43	in the
44	.BR SYNOPSIS ).
45	The second part will start at the first non\-option parameter that is
46	not an option argument, or after the first occurrence of
47	.RB ' \-\- '.
48	If no
49	.RB ' \-o '
50	or
51	.RB ' \-\-options '
52	option is found in the first part, the first parameter of the second
53	part is used as the short options string.
54	.PP
55	If the environment variable
56	.B GETOPT_COMPATIBLE
57	is set, or if the first \fIparameter\fR is not an option (does not start
58	with a
59	.RB ' \- ',
60	the first format in the
61	.BR SYNOPSIS ),
62	.B getopt
63	will generate output that is compatible with that of other versions of
64	.BR getopt (1).
65	It will still do parameter shuffling and recognize optional arguments
66	(see section
67	.B COMPATIBILITY
68	for more information).
69	.PP
70	Traditional implementations of
71	.BR getopt (1)
72	are unable to cope with whitespace and other (shell\-specific)
73	special characters in arguments and non\-option parameters. To solve
74	this problem, this implementation can generate quoted output which
75	must once again be interpreted by the shell (usually by using the
76	.B eval
77	command). This has the effect of preserving those characters, but
78	you must call
79	.B getopt
80	in a way that is no longer compatible with other versions (the second
81	or third format in the
82	.BR SYNOPSIS ).
83	To determine whether this enhanced version of
84	.BR getopt (1)
85	is installed, a special test option
86	.RB ( \-T )
87	can be used.
88	.SH OPTIONS
89	.TP
90	.BR \-a , " \-\-alternative"
91	Allow long options to start with a single
92	.RB ' \- '.
93	.TP
94	.BR \-h , " \-\-help"
95	Display help text and exit. No other output is generated.
96	.TP
97	.BR \-l , " \-\-longoptions \fIlongopts\fP"
98	The long (multi\-character) options to be recognized. More than one
99	option name may be specified at once, by separating the names with
100	commas. This option may be given more than once, the
101	.I longopts
102	are cumulative. Each long option name in
103	.I longopts
104	may be followed by one colon to indicate it has a required argument,
105	and by two colons to indicate it has an optional argument.
106	.TP
107	.BR \-n , " \-\-name \fIprogname\fP"
108	The name that will be used by the
109	.BR getopt (3)
110	routines when it reports errors. Note that errors of
111	.BR getopt (1)
112	are still reported as coming from getopt.
113	.TP
114	.BR \-o , " \-\-options \fIshortopts\fP"
115	The short (one\-character) options to be recognized. If this option
116	is not found, the first parameter of
117	.B getopt
118	that does not start with a
119	.RB ' \- '
120	(and is not an option argument) is used as the short options string.
121	Each short option character in
122	.I shortopts
123	may be followed by one colon to indicate it has a required argument,
124	and by two colons to indicate it has an optional argument. The first
125	character of shortopts may be
126	.RB ' + '
127	or
128	.RB ' \- '
129	to influence the way options are parsed and output is generated (see
130	section
131	.B SCANNING MODES
132	for details).
133	.TP
134	.BR \-q , " \-\-quiet"
135	Disable error reporting by getopt(3).
136	.TP
137	.BR \-Q , " \-\-quiet\-output"
138	Do not generate normal output. Errors are still reported by
139	.BR getopt (3),
140	unless you also use
141	.BR \-q .
142	.TP
143	.BR \-s , " \-\-shell \fIshell\fP"
144	Set quoting conventions to those of \fIshell\fR.
145	If the \fB\-s\fR option is not given, the
146	.SM BASH
147	conventions are used. Valid arguments are currently
148	.RB ' sh '
149	.RB ' bash ',
150	.RB ' csh ',
151	and
152	.RB ' tcsh '.
153	.TP
154	.BR \-u , " \-\-unquoted"
155	Do not quote the output. Note that whitespace and special
156	(shell\-dependent) characters can cause havoc in this mode (like they
157	do with other
158	.BR getopt (1)
159	implementations).
160	.TP
161	.BR \-T , " \-\-test"
162	Test if your
163	.BR getopt (1)
164	is this enhanced version or an old version. This generates no
165	output, and sets the error status to 4. Other implementations of
166	.BR getopt (1),
167	and this version if the environment variable
168	.B GETOPT_COMPATIBLE
169	is set, will return
170	.RB ' \-\- '
171	and error status 0.
172	.TP
173	.BR \-V , " \-\-version"
174	Display version information and exit. No other output is generated.
175	.SH PARSING
176	This section specifies the format of the second part of the
177	parameters of
178	.B getopt
179	(the
180	.I parameters
181	in the
182	.BR SYNOPSIS ).
183	The next section
184	.RB ( OUTPUT )
185	describes the output that is generated. These parameters were
186	typically the parameters a shell function was called with. Care must
187	be taken that each parameter the shell function was called with
188	corresponds to exactly one parameter in the parameter list of
189	.B getopt
190	(see the
191	.BR EXAMPLES ).
192	All parsing is done by the GNU
193	.BR getopt (3)
194	routines.
195	.PP
196	The parameters are parsed from left to right. Each parameter is
197	classified as a short option, a long option, an argument to an
198	option, or a non\-option parameter.
199	.PP
200	A simple short option is a
201	.RB ' \- '
202	followed by a short option character. If the option has a required
203	argument, it may be written directly after the option character or as
204	the next parameter (i.e. separated by whitespace on the command
205	line). If the option has an optional argument, it must be written
206	directly after the option character if present.
207	.PP
208	It is possible to specify several short options after one
209	.RB ' \- ',
210	as long as all (except possibly the last) do not have required or
211	optional arguments.
212	.PP
213	A long option normally begins with
214	.RB ' \-\- '
215	followed by the long option name. If the option has a required
216	argument, it may be written directly after the long option name,
217	separated by
218	.RB ' = ',
219	or as the next argument (i.e. separated by whitespace on the command
220	line). If the option has an optional argument, it must be written
221	directly after the long option name, separated by
222	.RB ' = ',
223	if present (if you add the
224	.RB ' = '
225	but nothing behind it, it is interpreted as if no argument was
226	present; this is a slight bug, see the
227	.BR BUGS ).
228	Long options may be abbreviated, as long as the abbreviation is not
229	ambiguous.
230	.PP
231	Each parameter not starting with a
232	.RB ' \- ',
233	and not a required argument of a previous option, is a non\-option
234	parameter. Each parameter after a
235	.RB ' \-\- '
236	parameter is always interpreted as a non\-option parameter. If the
237	environment variable
238	.B POSIXLY_CORRECT
239	is set, or if the short option string started with a
240	.RB ' + ',
241	all remaining parameters are interpreted as non\-option parameters as
242	soon as the first non\-option parameter is found.
243	.SH OUTPUT
244	Output is generated for each element described in the previous
245	section. Output is done in the same order as the elements are
246	specified in the input, except for non\-option parameters. Output
247	can be done in
248	.I compatible
249	.RI ( unquoted )
250	mode, or in such way that whitespace and other special characters
251	within arguments and non\-option parameters are preserved (see
252	.BR QUOTING ).
253	When the output is processed in the shell script, it will seem to be
254	composed of distinct elements that can be processed one by one (by
255	using the shift command in most shell languages). This is imperfect
256	in unquoted mode, as elements can be split at unexpected places if
257	they contain whitespace or special characters.
258	.PP
259	If there are problems parsing the parameters, for example because a
260	required argument is not found or an option is not recognized, an
261	error will be reported on stderr, there will be no output for the
262	offending element, and a non\-zero error status is returned.
263	.PP
264	For a short option, a single
265	.RB ' \- '
266	and the option character are generated as one parameter. If the
267	option has an argument, the next parameter will be the argument. If
268	the option takes an optional argument, but none was found, the next
269	parameter will be generated but be empty in quoting mode, but no
270	second parameter will be generated in unquoted (compatible) mode.
271	Note that many other
272	.BR getopt (1)
273	implementations do not support optional arguments.
274	.PP
275	If several short options were specified after a single
276	.RB ' \- ',
277	each will be present in the output as a separate parameter.
278	.PP
279	For a long option,
280	.RB ' \-\- '
281	and the full option name are generated as one parameter. This is
282	done regardless whether the option was abbreviated or specified with
283	a single
284	.RB ' \- '
285	in the input. Arguments are handled as with short options.
286	.PP
287	Normally, no non\-option parameters output is generated until all
288	options and their arguments have been generated. Then
289	.RB ' \-\- '
290	is generated as a single parameter, and after it the non\-option
291	parameters in the order they were found, each as a separate
292	parameter. Only if the first character of the short options string
293	was a
294	.RB ' \- ',
295	non\-option parameter output is generated at the place they are found
296	in the input (this is not supported if the first format of the
297	.B SYNOPSIS
298	is used; in that case all preceding occurrences of
299	.RB ' \- '
300	and
301	.RB ' + '
302	are ignored).
303	.SH QUOTING
304	In compatible mode, whitespace or 'special' characters in arguments
305	or non\-option parameters are not handled correctly. As the output
306	is fed to the shell script, the script does not know how it is
307	supposed to break the output into separate parameters. To circumvent
308	this problem, this implementation offers quoting. The idea is that
309	output is generated with quotes around each parameter. When this
310	output is once again fed to the shell (usually by a shell
311	.B eval
312	command), it is split correctly into separate parameters.
313	.PP
314	Quoting is not enabled if the environment variable
315	.B GETOPT_COMPATIBLE
316	is set, if the first form of the
317	.B SYNOPSIS
318	is used, or if the option
319	.RB ' \-u '
320	is found.
321	.PP
322	Different shells use different quoting conventions. You can use the
323	.RB ' \-s '
324	option to select the shell you are using. The following shells are
325	currently supported:
326	.RB ' sh ',
327	.RB ' bash ',
328	.RB ' csh '
329	and
330	.RB ' tcsh '.
331	Actually, only two 'flavors' are distinguished: sh\-like quoting
332	conventions and csh\-like quoting conventions. Chances are that if
333	you use another shell script language, one of these flavors can still
334	be used.
335	.SH "SCANNING MODES"
336	The first character of the short options string may be a
337	.RB ' \- '
338	or a
339	.RB ' + '
340	to indicate a special scanning mode. If the first calling form in
341	the
342	.B SYNOPSIS
343	is used they are ignored; the environment variable
344	.B POSIXLY_CORRECT
345	is still examined, though.
346	.PP
347	If the first character is
348	.RB ' + ',
349	or if the environment variable
350	.B POSIXLY_CORRECT
351	is set, parsing stops as soon as the first non\-option parameter
352	(i.e. a parameter that does not start with a
353	.RB ' \- ')
354	is found that is not an option argument. The remaining parameters
355	are all interpreted as non\-option parameters.
356	.PP
357	If the first character is a
358	.RB ' \- ',
359	non\-option parameters are outputted at the place where they are
360	found; in normal operation, they are all collected at the end of
361	output after a
362	.RB ' \-\- '
363	parameter has been generated. Note that this
364	.RB ' \-\- '
365	parameter is still generated, but it will always be the last
366	parameter in this mode.
367	.SH COMPATIBILITY
368	This version of
369	.BR getopt (1)
370	is written to be as compatible as possible to other versions.
371	Usually you can just replace them with this version without any
372	modifications, and with some advantages.
373	.PP
374	If the first character of the first parameter of getopt is not a
375	.RB ' \- ',
376	.B getopt
377	goes into compatibility mode. It will interpret its first
378	parameter as the string of short options, and all other arguments
379	will be parsed. It will still do parameter shuffling (i.e. all
380	non\-option parameters are output at the end), unless the
381	environment variable
382	.B POSIXLY_CORRECT
383	is set.
384	.PP
385	The environment variable
386	.B GETOPT_COMPATIBLE
387	forces
388	.B getopt
389	into compatibility mode. Setting both this environment variable and
390	.B POSIXLY_CORRECT
391	offers 100% compatibility for 'difficult' programs. Usually, though,
392	neither is needed.
393	.PP
394	In compatibility mode, leading
395	.RB ' \- '
396	and
397	.RB ' + '
398	characters in the short options string are ignored.
399	.SH RETURN CODES
400	.B getopt
401	returns error code
402	.B 0
403	for successful parsing,
404	.B 1
405	if
406	.BR getopt (3)
407	returns errors,
408	.B 2
409	if it does not understand its own parameters,
410	.B 3
411	if an internal error occurs like out\-of\-memory, and
412	.B 4
413	if it is called with
414	.BR \-T .
415	.SH EXAMPLES
416	Example scripts for (ba)sh and (t)csh are provided with the
417	.BR getopt (1)
418	distribution, and are optionally installed in
419	.BR /usr/local/share/getopt/
420	or
421	.BR /usr/share/getopt/ .
422	.SH ENVIRONMENT
423	.IP POSIXLY_CORRECT
424	This environment variable is examined by the
425	.BR getopt (3)
426	routines. If it is set, parsing stops as soon as a parameter is
427	found that is not an option or an option argument. All remaining
428	parameters are also interpreted as non\-option parameters, regardless
429	whether they start with a
430	.RB ' \- '.
431	.IP GETOPT_COMPATIBLE
432	Forces
433	.B getopt
434	to use the first calling format as specified in the
435	.BR SYNOPSIS .
436	.SH BUGS
437	.BR getopt (3)
438	can parse long options with optional arguments that are given an
439	empty optional argument (but can not do this for short options).
440	This
441	.BR getopt (1)
442	treats optional arguments that are empty as if they were not present.
443	.PP
444	The syntax if you do not want any short option variables at all is
445	not very intuitive (you have to set them explicitly to the empty
446	string).
447	.SH AUTHOR
448	.MT frodo@frodo.looijaard.name
449	Frodo Looijaard
450	.ME
451	.SH "SEE ALSO"
452	.BR getopt (3),
453	.BR bash (1),
454	.BR tcsh (1).
455	.SH AVAILABILITY
456	You can download the latest getopt from
457	.UR http://frodo.looijaard.name/project/getopt
458	the author's home page
459	.UE .
460	It is also part of the util-linux package which is available from
461	.UR ftp://\:ftp.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
462	Linux Kernel Archive
463	.UE .
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