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 <frodo@frodo.looijaard.name>
.SH "SEE ALSO"
.BR getopt (3),
.BR bash (1),
.BR tcsh (1).

1	frodo	259	.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	frodo	262	that is not an option argument, or after the first occurrence of
37	frodo	259	.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	frodo	262	The short (one\-character) options to be recognized. If this option is not
104	frodo	259	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	frodo	262	is used; in that case all preceding occurrences of
288	frodo	259	.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	263	Frodo Looijaard <frodo@frodo.looijaard.name>
437	frodo	259	.SH "SEE ALSO"
438			.BR getopt (3),
439			.BR bash (1),
440			.BR tcsh (1).
441
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