05fbeb03 |
1 | .\" -*-nroff-*- |
fbf20b5b |
2 | .TH mdwopt 3 "6 July 1999" "Straylight/Edgeware" "mLib utilities library" |
05fbeb03 |
3 | .SH "NAME" |
4 | mdwopt \- command-line option parser |
5 | .\" @mdwopt |
6 | .SH "SYNOPSIS" |
7 | .nf |
8 | .B "#include <mLib/mdwopt.h>" |
9 | |
10 | .BI "int mdwopt(int " argc ", char *const *" argv , |
11 | .BI " const char *" shortopt , |
12 | .BI " const struct option *" longopt ", int *" longind , |
13 | .BI " mdwopt_data *" data ", int " flags ); |
14 | |
15 | .BI "int getopt(int " argc ", char *const *" argv ", const char *" o ); |
16 | |
17 | .BI "int getopt_long(int " argc ", char *const *" argv , |
18 | .BI " const char * "shortopt , |
19 | .BI " const struct option *" longopt ", int *" longind ); |
20 | |
21 | .BI "int getopt_long_only(int " argc ", char *const *" argv , |
22 | .BI " const char * "shortopt , |
23 | .BI " const struct option *" longopt ", int *" longind ); |
24 | .fi |
25 | .SH "OVERVIEW" |
26 | The |
27 | .B mdwopt |
28 | function is a command line options parser which is (mostly) compatible |
29 | with the standard POSIX and GNU |
30 | .B getopt |
31 | functions, although provides more features than either. It's not the |
32 | most featureful options parser around, but it's good enough for my |
33 | purposes at the moment. |
34 | .SH "OPTION SYNTAX" |
35 | A command line consists of a number of |
36 | .I words |
37 | (which may contain spaces, according to various shell quoting |
38 | conventions). A word may be an option, an argument to an option, or a |
39 | non-option. An option begins with a special character, usually |
40 | .RB ` \- ', |
41 | although |
42 | .RB ` + ' |
43 | is also used sometimes. As special exceptions, the word containing only |
44 | a |
45 | .RB ` \- ' |
46 | is considered to be a non-option, since it usually represents standard |
47 | input or output as a filename, and the word containing only a |
48 | double-dash |
3751b763 |
49 | .RB ` \-\- ' |
05fbeb03 |
50 | is used to mark all following words as being non-options regardless of |
51 | their initial character. |
52 | .PP |
53 | Traditionally, all words after the first non-option have been considered |
54 | to be non-options automatically, so that options must be specified |
55 | before filenames. However, this implementation can extract all the |
56 | options from the command line regardless of their position. This can |
57 | usually be disabled by setting one of the environment variables |
58 | .B POSIXLY_CORRECT |
59 | or |
60 | .BR _POSIX_OPTION_ORDER . |
61 | .PP |
62 | There are two different styles of options: |
63 | .I short |
64 | and |
65 | .IR long . |
66 | Traditional Unix (and POSIX) only uses short options. The long options |
67 | are a GNU convention. |
68 | .SS "Short option syntax" |
69 | Short options are the sort which Unix has known for ages: an option is a |
70 | single letter, preceded by a |
3751b763 |
71 | .RB ` \- '. |
05fbeb03 |
72 | Short options can be joined together to save space (and possibly to make |
73 | silly words): e.g., instead of giving options |
74 | .RB ` "\-x \-y" ', |
75 | a user could write |
76 | .RB ` \-xy '. |
77 | Some short options can have arguments which appear after the option |
78 | letter, either immediately following, or in the next word; so an option |
79 | with an argument could be written as |
80 | .RB ` "\-o foo" ' |
81 | or as |
82 | .RB ` \-ofoo '). |
83 | Note that options with optional arguments must be written in the second |
84 | style. |
85 | .PP |
86 | When a short option controls a flag setting, it is sometimes possible to |
87 | explicitly turn the flag off, as well as turning it on, (usually to |
88 | override default options). This is usually done by using a |
89 | .RB ` + ' |
d4efbcd9 |
90 | instead of a |
05fbeb03 |
91 | .RB ` \- ' |
92 | to introduce the option. (Some programs use upper-case option letters |
93 | to indicate this instead.) |
94 | .SS "Long option syntax" |
95 | Long options, as popularized by the GNU utilities, are given long-ish |
96 | memorable names, preceded by a double-dash |
97 | .RB ` \-\- '. |
98 | Since their names are more than a single character, long options can't |
99 | be combined in the same way as short options. Arguments to long options |
100 | may be given either in the same word, separated from the option name by |
101 | an equals sign, or in the following word. |
102 | .PP |
103 | Long option names can be abbreviated if necessary, as long as the |
104 | abbreviation is unique. This means that options can have sensible and |
105 | memorable names but still not require much typing from an experienced |
106 | user. |
107 | .PP |
108 | Like short options, long options can control flag settings. The options |
109 | to manipulate these settings come in pairs: an option of the form |
110 | .RB ` \-\-set\-flag ' |
111 | might set the flag, while an option of the form |
112 | .RB ` \-\-no\-set\-flag ' |
113 | might clear it. |
114 | .PP |
115 | It is usual for applications to provide both short and long options with |
116 | identical behaviour. Some applications with lots of options may only |
117 | provide long options (although they will often be only two or three |
118 | characters long). In this case, long options can be preceded with a |
119 | single |
120 | .RB ` \- ' |
121 | character, and negated by a |
122 | .RB ` + ' |
123 | character. |
124 | .SS "Numerical options" |
125 | Finally, some (older) programs accept arguments of the form |
126 | .RB ` \- \c |
127 | .IR number ', |
128 | to set some numerical parameter, typically a line count of some kind. |
129 | .SH "PARSING OPTIONS WITH \fBmdwopt\fP" |
130 | An application parses its options by calling |
131 | .B mdwopt |
132 | repeatedly. Each time it is called, |
133 | .B mdwopt |
134 | returns a value describing the option just read, and stores information |
135 | about the option in a data block. |
136 | .PP |
137 | The data block is a structure containing at least the following members: |
138 | .TP |
ff76c38f |
139 | .B "char *arg" |
05fbeb03 |
140 | Pointer to the argument of the current option, or null. Argument |
141 | strings persist for as long as the underlying command line argument |
142 | array |
143 | .I argv |
144 | does, so it's usually safe just to remember the pointer. |
145 | .TP |
ff76c38f |
146 | .B "int opt" |
05fbeb03 |
147 | Value of the current option |
148 | .TP |
ff76c38f |
149 | .B "int ind" |
05fbeb03 |
150 | Must be initialized to 0 before the first call to |
151 | .BR mdwopt . |
152 | After the last call, it is the index into |
153 | .I argv |
154 | of the first nonoption argument. |
155 | .TP |
ff76c38f |
156 | .B "int err" |
05fbeb03 |
157 | Set to nonzero to allow |
158 | .B mdwopt |
159 | to emit error messages about illegal option syntax. (This would be a |
160 | flag setting, but it has to be here for |
161 | .B getopt |
162 | compatibility.) |
163 | .TP |
ff76c38f |
164 | .B "char *prog" |
05fbeb03 |
165 | Contains the program's name, stripped of any path prefix. This is an |
166 | obsolete feature: the |
167 | .BR quis (3) |
168 | module does the job in a more sensible way. |
169 | .PP |
170 | Prior to the first call to |
171 | .BR mdwopt , |
172 | the |
173 | .B err |
174 | and |
175 | .B ind |
3751b763 |
176 | members of the structure must be initialized. |
05fbeb03 |
177 | .PP |
178 | The arguments |
179 | .I argc |
180 | and |
181 | .I argv |
182 | describe the command-line argument array which is to be parsed. These |
183 | will usually be exactly the arguments passed to the program's |
184 | .B main |
185 | function. |
186 | .SS "Short option parsing" |
187 | Short options are described by a string, |
188 | .IR shortopt , |
189 | which once upon a time just contained the permitted option characters. |
190 | Now the options string begins with a collection of flag characters, and |
191 | various flag characters can be put after options characters to change |
192 | their properties. |
193 | .PP |
194 | If the first character of the short options string is |
195 | .RB ` + ', |
196 | .RB ` \- ' |
197 | or |
198 | .RB ` ! ', |
199 | the order in which options are read is modified, as follows: |
200 | .TP |
201 | .RB ` + ' |
202 | Forces the POSIX order to be used. As soon as a non-option is found, |
203 | .B mdwopt |
204 | returns \-1. |
205 | .TP |
206 | .RB ` \- ' |
207 | Makes |
208 | .B mdwopt |
209 | treat non-options as being `special' sorts of option. When a non-option |
210 | word is found, the value 0 is returned, and the actual text of the word |
211 | is stored as being the option's argument. |
212 | .TP |
213 | .RB ` ! ' |
214 | forces the default order to be used regardless of environment variable |
215 | settings. The entire command line is scanned for options, which are |
216 | returned in order. However, during this process, the options are moved |
217 | in the |
218 | .I argv |
219 | array, so that they appear before the non-options. |
220 | .PP |
221 | A |
222 | .RB ` : ' |
223 | character may be placed after the ordering flag (or at the very |
224 | beginning if no ordering flag is given) which indicates that the |
225 | character |
226 | .RB ` : ', |
227 | rather than |
228 | .RB ` ? ', |
229 | should be returned if a missing argument error is detected. |
230 | .PP |
231 | Each option in the string can be followed by a |
232 | .RB ` + ' |
233 | sign, indicating that it can be negated, a |
234 | .RB ` : ' |
235 | sign indicating that it requires an argument, or a |
236 | .RB ` :: ' |
237 | string, indicating an optional argument. Both |
238 | .RB ` + ' |
239 | and one of |
240 | .RB ` : ' |
241 | or |
242 | .RB ` :: ' |
243 | may be given, although the |
244 | .RB ` + ' |
245 | must come first. |
246 | .PP |
247 | If an option is found, the option character is returned to the caller. |
248 | A pointer to an argument is stored in the |
249 | .B arg |
250 | member of the data block; a null pointer is stored if there was no |
251 | argument. If a negated option was found, the option character is |
d2a91066 |
252 | returned ORed with |
05fbeb03 |
253 | .B OPTF_NEGATED |
254 | (bit 8 set). |
255 | .SS "Long option parsing" |
256 | Long options are described in a table. Each entry in the |
257 | table is of type |
258 | .BR "struct option" , |
259 | which contains the following members (in order): |
260 | .TP |
ff76c38f |
261 | .B "const char *name" |
05fbeb03 |
262 | Pointer to the option's name. |
263 | .TP |
ff76c38f |
264 | .B "int has_arg" |
05fbeb03 |
265 | A flags word describing the option. (The name is historical.) |
266 | .TP |
ff76c38f |
267 | .B "int *flag" |
05fbeb03 |
268 | Address of the flag variable to use when this option is matched. |
269 | .TP |
ff76c38f |
270 | .B "int val" |
05fbeb03 |
271 | Value to store or return when this option is matched. |
272 | .PP |
273 | The table is terminated by an entry whose |
274 | .B name |
275 | field is a null pointer. |
276 | .PP |
277 | When |
278 | .B mdwopt |
279 | finds a long option, it looks the name up in the table. The index of the |
280 | matching entry is stored in the |
281 | .I longind |
282 | variable, passed to |
283 | .B mdwopt |
d4efbcd9 |
284 | (unless |
05fbeb03 |
285 | .I longind |
286 | is null): a value of \-1 indicates that no long option was found. The |
287 | behaviour is then dependent on the values in the table entry. |
288 | .PP |
289 | If the flag bit |
290 | .B OPTF_ARGREQ |
291 | is set in |
292 | .B has_arg |
293 | then the option has a required argument, which may be separated from the |
294 | option name by an equals sign or placed in the following word. If the |
295 | flag bit |
296 | .B OPTF_ARGOPT |
297 | is set then the argument is optional. If present, the argument must be |
298 | in the same word as the option name, separated by an equals sign. It is |
299 | an error for both flags to be set; if neither is set then the option |
300 | does not take an argument. |
301 | .PP |
302 | If |
303 | .B flag |
304 | is nonzero, it points to an integer to be modified by |
305 | .BR mdwopt . |
306 | Usually the value in the |
307 | .B val |
308 | field is simply stored in the |
309 | .B flag |
310 | variable. If the flag |
311 | .B OPTF_SWITCH |
312 | is set in the |
313 | .B has_arg |
314 | member, however, the value is combined with the existing value of the |
315 | flags using a bitwise OR. If |
316 | .B OPTF_NEGATE |
317 | is set in the |
318 | .B has_arg |
319 | field, then the flag bit will be cleared if a matching negated long |
320 | option is found. The value 0 is returned. |
321 | .PP |
322 | If |
323 | .B flag |
324 | is zero, the value in |
325 | .B val |
326 | is returned by |
327 | .BR mdwopt , |
328 | possibly with bit 8 set if the option was |
329 | negated. |
330 | .PP |
3751b763 |
331 | Arguments from long options are stored in the |
05fbeb03 |
332 | .B arg |
3751b763 |
333 | member of the data block. |
05fbeb03 |
334 | .SS "Other optional features" |
335 | The |
336 | .I flags |
337 | argument contains a bitmask of features which may be enabled: |
338 | .TP |
339 | .B OPTF_NOLONGS |
340 | Don't allow any long options. This makes |
341 | .B mdwopt |
342 | compatible with traditional Unix |
343 | .BR getopt . |
344 | .TP |
345 | .B OPTF_NOSHORTS |
346 | A slightly misnamed flag. Short options are read normally. However, |
347 | long options may also begin with a single dash |
348 | .RB ` \- ' |
349 | (or the |
350 | .RB ` + ' |
351 | sign if negated). Long options may not be combined with short options: |
352 | an option word which begins with a short option must contain only short |
353 | options. |
354 | .TP |
355 | .B OPTF_NUMBERS |
356 | Read numeric options. If a numeric option is found, the character |
357 | .RB ` # ' |
358 | is returned and the text of the number is stored in the |
359 | .B arg |
360 | member of the data block. |
361 | .TP |
362 | .B OPTF_NEGATION |
363 | Allow negation of options. Negated options are returned ORed with |
364 | .BR OPTF_NEGATED . |
365 | .TP |
366 | .B OPTF_ENVVAR |
367 | Options will be read from an environment variable before scanning the |
368 | actual command line provided. The name of the environment variable is |
369 | found by capitalizing the program name. (This allows a user to have |
370 | different default settings for a program, by calling it through |
371 | different symbolic links.) |
372 | .TP |
373 | .B OPTF_NOPROGNAME |
374 | Don't read the program name from |
375 | .IR argv \c |
376 | .BR [0] , |
377 | and don't set the |
378 | .B prog |
379 | data block member. Options start right at the beginning of |
380 | .IR argv . |
381 | .TP |
382 | .B OPTF_NEGNUMBER |
383 | Allow negated numeric options. Negated numeric options begin with a |
384 | .RB ` + ' |
385 | rather than a |
386 | .RB ` \- '. |
387 | The return value is |
388 | .RB ` # ' " | OPTF_NEGATED" . |
389 | .SS "Compatibility features" |
390 | The macros |
391 | .BR getopt , |
392 | .B getopt_long |
393 | and |
394 | .B getopt_long_only |
395 | correspond to calls to |
396 | .B mdwopt |
397 | with various flag settings. See the macro definitions for the actual |
398 | mappings, and the documentation for the functions to see how they're |
399 | meant to work. |
400 | .PP |
401 | Additionally, there is a global data block, which is specified by |
402 | passing a null |
403 | .I data |
404 | argument to |
405 | .BR mdwopt . |
406 | The members of this block may be referred to by their traditional names: |
407 | .TP |
408 | .B optarg |
409 | The argument of the current option. |
410 | .TP |
411 | .B optopt |
412 | Option code of the current option. |
413 | .TP |
414 | .B opterr |
415 | Nonzero if |
416 | .B mdwopt |
417 | is to report errors. This is the default. |
418 | .TP |
419 | .B optind |
420 | Index of the first non-option argument. |
421 | .TP |
422 | .B optprog |
423 | Name of the program, stripped of path prefix. |
424 | .PP |
425 | These names aren't considered deprecated: they help make the code easier |
426 | to read by people used to the traditional |
427 | .B getopt |
428 | function. |
429 | .SH "SEE ALSO" |
430 | .BR getopt (3), |
431 | .BR mLib (3). |
432 | .SH "AUTHOR" |
9b5ac6ff |
433 | Mark Wooding, <mdw@distorted.org.uk> |