getopt/trunk/getopt.1

.TH GETOPT 1 "May 31, 1997" Linux ""
.SH NAME
getopt \- parse command options (enhanced)
.SH SYNOPSIS
.BR getopt " optstring parameters"

.BR getopt " [options] [" \-\- "] optstring parameters"

.BR getopt " [options] " \-o | \-\-options " optstring [options] [" \-\- "] 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.

The parameters 
.B getopt
is called with can be divided into two parts: options
which modify the way getopt will parse
.RI ( options
and
.I \-o|\-\-options 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.

If the environment variable
.B GETOPT_COMPATIBLE
is set, or if its first parameter 
is not an option (does not start with a
.RB ` \- ',
this is 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). 

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
.IP "\-a, \-\-alternative"
Allow long options to start with a single 
.RB ` \- '.
.IP "\-h, \-\-help"
Output a small usage guide and exit succesfully. No other output is generated. 
.IP "\-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 
.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.
.IP "\-n, \-\-name progname"
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.
.IP "\-o, \-\-options shortopts"
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).
.IP "\-q, \-\-quiet"
Disable error reporting by getopt(3).
.IP "\-Q, \-\-quiet\-output"
Do not generate normal output. Errors are still reported by
.BR getopt (3), 
unless you also use 
.IR \-q .
.IP "\-s, \-\-shell shell"
Set quoting conventions to those of shell. If no \-s argument is found,
the
.SM BASH
conventions are used. Valid arguments are currently
.RB ` sh '
.RB ` bash ',
.RB ` csh ',
and
.RB ` tcsh '.
.IP "\-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).
.IP "\-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.
.IP "\-V, \-\-version"
Output version information and exit succesfully. 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. 

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 
.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 (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 
.RB ` \- ', 
as long as all (except possibly the last) do not have required or optional
arguments.

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 (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 
.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.

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.

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 
.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) 
implemetations do not support optional arguments.

If several short options were specified after a single 
.RB ` \- ', 
each will be present in the output as a separate parameter.

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.

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.

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.

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.

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 
(ie. 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.

If the first character is a
.RB ` \- ',
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 
.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.

If the first character of the first parameter of getopt is not a 
.RB ` \- ', 
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 environment variable 
.B POSIXLY_CORRECT 
is set.

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.

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 succesful 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 
.B /usr/local/lib/getopt 
or 
.BR /usr/lib/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.

The syntax if you do not want any short option variables at all is
not very intuitive (you have to set them explicitely to the empty
string).

.SH AUTHOR
Frodo Looijaard <frodol@dds.nl>
.SH "SEE ALSO"
.BR getopt (3),
.BR bash (1),
.BR tcsh (1).

1	.TH GETOPT 1 "May 31, 1997" Linux ""
2	.SH NAME
3	getopt \- parse command options (enhanced)
4	.SH SYNOPSIS
5	.BR getopt " optstring parameters"
6
7	.BR getopt " [options] [" \-\- "] optstring parameters"
8
9	.BR getopt " [options] " \-o \| \-\-options " optstring [options] [" \-\- "] parameters"
10	.SH DESCRIPTION
11	.B getopt
12	is used to break up
13	.RI ( parse )
14	options in command lines for easy parsing by
15	shell procedures, and to check for legal options.
16	It uses the
17	.SM GNU
18	.BR getopt (3)
19	routines to do this.
20
21	The parameters
22	.B getopt
23	is called with can be divided into two parts: options
24	which modify the way getopt will parse
25	.RI ( options
26	and
27	.I \-o\|\-\-options optstring
28	in the
29	.BR SYNOPSIS),
30	and the parameters which are to be
31	parsed
32	.RI ( parameters
33	in the
34	.BR SYNOPSIS).
35	The second part will start at the first non\-option parameter
36	that is not an option argument, or after the first occurrence of
37	.RB ` \-\- '.
38	If no
39	.RB ` \-o '
40	or
41	.RB ` \-\-options '
42	option is found in the first part, the first
43	parameter of the second part is used as the short options string.
44
45	If the environment variable
46	.B GETOPT_COMPATIBLE
47	is set, or if its first parameter
48	is not an option (does not start with a
49	.RB ` \- ',
50	this is the first format in the
51	.BR SYNOPSIS),
52	.B getopt
53	will generate output that is compatible with that of other versions of
54	.BR getopt (1).
55	It will still do parameter shuffling and recognize optional
56	arguments (see section
57	.B COMPATIBILITY
58	for more information).
59
60	Traditional implementations of
61	.BR getopt (1)
62	are unable to cope with whitespace and other (shell\-specific) special characters
63	in arguments and non\-option parameters. To solve this problem, this
64	implementation can generate
65	quoted output which must once again be interpreted by the shell (usually
66	by using the
67	.B eval
68	command). This has the effect of preserving those characters, but
69	you must call
70	.B getopt
71	in a way that is no longer compatible with other versions (the second
72	or third format in the
73	.BR SYNOPSIS).
74	To determine whether this enhanced version of
75	.BR getopt (1)
76	is installed, a special test option
77	.RB ( \-T )
78	can be used.
79	.SH OPTIONS
80	.IP "\-a, \-\-alternative"
81	Allow long options to start with a single
82	.RB ` \- '.
83	.IP "\-h, \-\-help"
84	Output a small usage guide and exit succesfully. No other output is generated.
85	.IP "\-l, \-\-longoptions longopts"
86	The long (multi\-character) options to be recognized.
87	More than one option name
88	may be specified at once, by separating the names with commas. This option
89	may be given more than once, the
90	.I longopts
91	are cumulative.
92	Each long option name
93	in
94	.I longopts
95	may be followed by one colon to indicate it has a required argument,and by two colons to indicate it has an optional argument.
96	.IP "\-n, \-\-name progname"
97	The name that will be used by the
98	.BR getopt (3)
99	routines when it reports errors. Note that errors of
100	.BR getopt (1)
101	are still reported as coming from getopt.
102	.IP "\-o, \-\-options shortopts"
103	The short (one\-character) options to be recognized. If this option is not
104	found, the first parameter of
105	.B getopt
106	that does not start with
107	a
108	.RB ` \- '
109	(and is not an option argument) is used as the short options string.
110	Each short option character
111	in
112	.I shortopts
113	may be followed by one colon to indicate it has a required argument,
114	and by two colons to indicate it has an optional argument.
115	The first character of shortopts may be
116	.RB ` + '
117	or
118	.RB ` \- '
119	to influence the way
120	options are parsed and output is generated (see section
121	.B SCANNING MODES
122	for details).
123	.IP "\-q, \-\-quiet"
124	Disable error reporting by getopt(3).
125	.IP "\-Q, \-\-quiet\-output"
126	Do not generate normal output. Errors are still reported by
127	.BR getopt (3),
128	unless you also use
129	.IR \-q .
130	.IP "\-s, \-\-shell shell"
131	Set quoting conventions to those of shell. If no \-s argument is found,
132	the
133	.SM BASH
134	conventions are used. Valid arguments are currently
135	.RB ` sh '
136	.RB ` bash ',
137	.RB ` csh ',
138	and
139	.RB ` tcsh '.
140	.IP "\-u, \-\-unquoted"
141	Do not quote the output. Note that whitespace and special (shell\-dependent)
142	characters can cause havoc in this mode (like they do with other
143	.BR getopt (1)
144	implementations).
145	.IP "\-T \-\-test"
146	Test if your
147	.BR getopt (1)
148	is this enhanced version or an old version. This generates no output,
149	and sets the error status to 4. Other implementations of
150	.BR getopt (1),
151	and this version if the environment variable
152	.B GETOPT_COMPATIBLE
153	is set,
154	will return
155	.RB ` \-\- '
156	and error status 0.
157	.IP "\-V, \-\-version"
158	Output version information and exit succesfully. No other output is generated.
159	.SH PARSING
160	This section specifies the format of the second part of the parameters of
161	.B getopt
162	(the
163	.I parameters
164	in the
165	.BR SYNOPSIS ).
166	The next section
167	.RB ( OUTPUT )
168	describes the output that is
169	generated. These parameters were typically the parameters a shell function
170	was called with.
171	Care must be taken that each parameter the shell function was
172	called with corresponds to exactly one parameter in the parameter list of
173	.B getopt
174	(see the
175	.BR EXAMPLES ).
176	All parsing is done by the GNU
177	.BR getopt (3)
178	routines.
179
180	The parameters are parsed from left to right. Each parameter is classified as a
181	short option, a long option, an argument to an option,
182	or a non\-option parameter.
183
184	A simple short option is a
185	.RB ` \- '
186	followed by a short option character. If
187	the option has a required argument, it may be written directly after the option
188	character or as the next parameter (ie. separated by whitespace on the
189	command line). If the
190	option has an optional argument, it must be written directly after the
191	option character if present.
192
193	It is possible to specify several short options after one
194	.RB ` \- ',
195	as long as all (except possibly the last) do not have required or optional
196	arguments.
197
198	A long option normally begins with
199	.RB ` \-\- '
200	followed by the long option name.
201	If the option has a required argument, it may be written directly after
202	the long option name, separated by
203	.RB ` = ',
204	or as the next argument (ie. separated by whitespace on the command line).
205	If the option has an optional argument, it must
206	be written directly after the long option name, separated by
207	.RB ` = ',
208	if present (if you add the
209	.RB ` = '
210	but nothing behind it, it is interpreted
211	as if no argument was present; this is a slight bug, see the
212	.BR BUGS ).
213	Long options may be abbreviated, as long as the abbreviation is not
214	ambiguous.
215
216	Each parameter not starting with a
217	.RB ` \- ',
218	and not a required argument of
219	a previous option, is a non\-option parameter. Each parameter after
220	a
221	.RB ` \-\- '
222	parameter is always interpreted as a non\-option parameter.
223	If the environment variable
224	.B POSIXLY_CORRECT
225	is set, or if the short
226	option string started with a
227	.RB ` + ',
228	all remaining parameters are interpreted
229	as non\-option parameters as soon as the first non\-option parameter is
230	found.
231	.SH OUTPUT
232	Output is generated for each element described in the previous section.
233	Output is done
234	in the same order as the elements are specified in the input, except
235	for non\-option parameters. Output can be done in
236	.I compatible
237	.RI ( unquoted )
238	mode, or in such way that whitespace and other special characters within
239	arguments and non\-option parameters are preserved (see
240	.BR QUOTING ).
241	When the output is processed in the shell script, it will seem to be
242	composed of distinct elements that can be processed one by one (by using the
243	shift command in most shell languages). This is imperfect in unquoted mode,
244	as elements can be split at unexpected places if they contain whitespace
245	or special characters.
246
247	If there are problems parsing the parameters, for example because a
248	required argument is not found or an option is not recognized, an error
249	will be reported on stderr, there will be no output for the offending
250	element, and a non\-zero error status is returned.
251
252	For a short option, a single
253	.RB ` \- '
254	and the option character are generated
255	as one parameter. If the option has an argument, the next
256	parameter will be the argument. If the option takes an optional argument,
257	but none was found, the next parameter will be generated but be empty in
258	quoting mode,
259	but no second parameter will be generated in unquoted (compatible) mode.
260	Note that many other
261	.BR getopt (1)
262	implemetations do not support optional arguments.
263
264	If several short options were specified after a single
265	.RB ` \- ',
266	each will be present in the output as a separate parameter.
267
268	For a long option,
269	.RB ` \-\- '
270	and the full option name are generated as one
271	parameter. This is done regardless whether the option was abbreviated or
272	specified with a single
273	.RB ` \- '
274	in the input. Arguments are handled as with short options.
275
276	Normally, no non\-option parameters output is generated until all options
277	and their arguments have been generated. Then
278	.RB ` \-\- '
279	is generated as a
280	single parameter, and after it the non\-option parameters in the order
281	they were found, each as a separate parameter.
282	Only if the first character of the short options string was a
283	.RB ` \- ',
284	non\-option parameter output is generated at the place they are found in the
285	input (this is not supported if the first format of the
286	.B SYNOPSIS
287	is used; in that case all preceding occurrences of
288	.RB ` \- '
289	and
290	.RB ` + '
291	are ignored).
292	.SH QUOTING
293	In compatible mode, whitespace or 'special' characters in arguments or
294	non\-option parameters are not handled correctly. As the output is
295	fed to the shell script, the script does not know how it is supposed to break
296	the output into separate parameters. To circumvent this
297	problem, this implementation offers quoting. The idea is that output
298	is generated with quotes around each parameter. When this output is once
299	again fed to the shell (usually by a shell
300	.B eval
301	command), it is split correctly into separate parameters.
302
303	Quoting is not enabled if the environment variable
304	.B GETOPT_COMPATIBLE
305	is set, if the first form of the
306	.B SYNOPSIS
307	is used, or if the option
308	.RB ` \-u '
309	is found.
310
311	Different shells use different quoting conventions. You can use the
312	.RB ` \-s '
313	option to select the shell you are using. The following shells are
314	currently supported:
315	.RB ` sh ',
316	.RB ` bash ',
317	.RB ` csh '
318	and
319	.RB ` tcsh '.
320	Actually, only two `flavors' are distinguished: sh\-like quoting conventions
321	and csh\-like quoting conventions. Chances are that if you use another shell
322	script language, one of these flavors can still be used.
323
324	.SH "SCANNING MODES"
325	The first character of the short options string may be a
326	.RB ` \- '
327	or a
328	.RB ` + '
329	to indicate a special scanning mode. If the first calling form
330	in the
331	.B SYNOPSIS
332	is used they are ignored; the environment variable
333	.B POSIXLY_CORRECT
334	is still examined, though.
335
336	If the first character is
337	.RB ` + ',
338	or if the environment variable
339	.B POSIXLY_CORRECT
340	is set, parsing stops as soon as the first non\-option parameter
341	(ie. a parameter that does not start with a
342	.RB ` \- ')
343	is found that
344	is not an option argument. The remaining parameters are all interpreted as
345	non\-option parameters.
346
347	If the first character is a
348	.RB ` \- ',
349	non\-option parameters are outputed at the place where they are found; in normal
350	operation, they are all collected at the end of output after a
351	.RB ` \-\- '
352	parameter has been generated. Note that this
353	.RB ` \-\- '
354	parameter is still generated, but it will always be the last parameter in
355	this mode.
356	.SH COMPATIBILITY
357	This version of
358	.BR getopt (1)
359	is written to be as compatible as possible to
360	other versions. Usually you can just replace them with this version
361	without any modifications, and with some advantages.
362
363	If the first character of the first parameter of getopt is not a
364	.RB ` \- ',
365	getopt goes into compatibility mode. It will interpret its first parameter as
366	the string of short options, and all other arguments will be parsed. It
367	will still do parameter shuffling (ie. all non\-option parameters are outputed
368	at the end), unless the environment variable
369	.B POSIXLY_CORRECT
370	is set.
371
372	The environment variable
373	.B GETOPT_COMPATIBLE
374	forces
375	.B getopt
376	into compatibility mode. Setting both this environment variable and
377	.B POSIXLY_CORRECT
378	offers 100% compatibility for `difficult' programs. Usually, though,
379	neither is needed.
380
381	In compatibility mode, leading
382	.RB ` \- '
383	and
384	.RB ` + '
385	characters in the short options string are ignored.
386	.SH RETURN CODES
387	.B getopt
388	returns error code
389	.B 0
390	for succesful parsing,
391	.B 1
392	if
393	.BR getopt (3)
394	returns errors,
395	.B 2
396	if it does not understand its own parameters,
397	.B 3
398	if an internal error occurs like out\-of\-memory, and
399	.B 4
400	if it is called with
401	.BR \-T .
402	.SH EXAMPLES
403	Example scripts for (ba)sh and (t)csh are provided with the
404	.BR getopt (1)
405	distribution, and are optionally installed in
406	.B /usr/local/lib/getopt
407	or
408	.BR /usr/lib/getopt .
409	.SH ENVIRONMENT
410	.IP POSIXLY_CORRECT
411	This environment variable is examined by the
412	.BR getopt (3)
413	routines.
414	If it is set, parsing stops as soon as a parameter
415	is found that is not an option or an option argument. All remaining
416	parameters are also interpreted as non\-option parameters, regardless
417	whether they start with a
418	.RB ` \- '.
419	.IP GETOPT_COMPATIBLE
420	Forces
421	.B getopt
422	to use the first calling format as specified in the
423	.BR SYNOPSIS .
424	.SH BUGS
425	.BR getopt (3)
426	can parse long options with optional arguments that are given an empty optional
427	argument (but can not do this for short options). This
428	.BR getopt (1)
429	treats optional arguments that are empty as if they were not present.
430
431	The syntax if you do not want any short option variables at all is
432	not very intuitive (you have to set them explicitely to the empty
433	string).
434
435	.SH AUTHOR
436	Frodo Looijaard <frodol@dds.nl>
437	.SH "SEE ALSO"
438	.BR getopt (3),
439	.BR bash (1),
440	.BR tcsh (1).
441
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