| 1 | .\" -*-nroff-*- |
| 2 | .TH mdwopt 3 "6 July 1999" "Straylight/Edgeware" "mLib utilities library" |
| 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 |
| 49 | .RB ` \-\- ' |
| 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 |
| 71 | .RB ` \- '. |
| 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 ` + ' |
| 90 | instead of a |
| 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 |
| 139 | .B "char *arg" |
| 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 |
| 146 | .B "int opt" |
| 147 | Value of the current option |
| 148 | .TP |
| 149 | .B "int ind" |
| 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 |
| 156 | .B "int err" |
| 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 |
| 164 | .B "char *prog" |
| 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 |
| 176 | members of the structure must be initialized. |
| 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 |
| 252 | returned ORed with |
| 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 |
| 261 | .B "const char *name" |
| 262 | Pointer to the option's name. |
| 263 | .TP |
| 264 | .B "int has_arg" |
| 265 | A flags word describing the option. (The name is historical.) |
| 266 | .TP |
| 267 | .B "int *flag" |
| 268 | Address of the flag variable to use when this option is matched. |
| 269 | .TP |
| 270 | .B "int val" |
| 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 |
| 284 | (unless |
| 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 |
| 331 | Arguments from long options are stored in the |
| 332 | .B arg |
| 333 | member of the data block. |
| 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" |
| 433 | Mark Wooding, <mdw@distorted.org.uk> |