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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 occurence 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 options 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 occurences 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

frodo@frodo.looijaard.name
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