]>
Commit | Line | Data |
---|---|---|
530e741c JH |
1 | parse-options API |
2 | ================= | |
3 | ||
2de9b711 | 4 | The parse-options API is used to parse and massage options in Git |
224712e5 | 5 | and to provide a usage help with consistent look. |
530e741c | 6 | |
224712e5 SB |
7 | Basics |
8 | ------ | |
9 | ||
10 | The argument vector `argv[]` may usually contain mandatory or optional | |
11 | 'non-option arguments', e.g. a filename or a branch, and 'options'. | |
12 | Options are optional arguments that start with a dash and | |
13 | that allow to change the behavior of a command. | |
14 | ||
15 | * There are basically three types of options: | |
16 | 'boolean' options, | |
17 | options with (mandatory) 'arguments' and | |
18 | options with 'optional arguments' | |
19 | (i.e. a boolean option that can be adjusted). | |
20 | ||
21 | * There are basically two forms of options: | |
22 | 'Short options' consist of one dash (`-`) and one alphanumeric | |
23 | character. | |
6cf378f0 | 24 | 'Long options' begin with two dashes (`--`) and some |
224712e5 SB |
25 | alphanumeric characters. |
26 | ||
27 | * Options are case-sensitive. | |
28 | Please define 'lower-case long options' only. | |
29 | ||
30 | The parse-options API allows: | |
31 | ||
b0d12fc9 NV |
32 | * 'stuck' and 'separate form' of options with arguments. |
33 | `-oArg` is stuck, `-o Arg` is separate form. | |
34 | `--option=Arg` is stuck, `--option Arg` is separate form. | |
224712e5 SB |
35 | |
36 | * Long options may be 'abbreviated', as long as the abbreviation | |
37 | is unambiguous. | |
38 | ||
39 | * Short options may be bundled, e.g. `-a -b` can be specified as `-ab`. | |
40 | ||
41 | * Boolean long options can be 'negated' (or 'unset') by prepending | |
6cf378f0 | 42 | `no-`, e.g. `--no-abbrev` instead of `--abbrev`. Conversely, |
0f1930c5 | 43 | options that begin with `no-` can be 'negated' by removing it. |
8a09e6c5 MH |
44 | Other long options can be unset (e.g., set string to NULL, set |
45 | integer to 0) by prepending `no-`. | |
224712e5 | 46 | |
6cf378f0 JK |
47 | * Options and non-option arguments can clearly be separated using the `--` |
48 | option, e.g. `-a -b --option -- --this-is-a-file` indicates that | |
49 | `--this-is-a-file` must not be processed as an option. | |
224712e5 SB |
50 | |
51 | Steps to parse options | |
52 | ---------------------- | |
53 | ||
54 | . `#include "parse-options.h"` | |
55 | ||
56 | . define a NULL-terminated | |
57 | `static const char * const builtin_foo_usage[]` array | |
58 | containing alternative usage strings | |
59 | ||
60 | . define `builtin_foo_options` array as described below | |
61 | in section 'Data Structure'. | |
62 | ||
63 | . in `cmd_foo(int argc, const char **argv, const char *prefix)` | |
64 | call | |
65 | ||
37782920 | 66 | argc = parse_options(argc, argv, prefix, builtin_foo_options, builtin_foo_usage, flags); |
224712e5 SB |
67 | + |
68 | `parse_options()` will filter out the processed options of `argv[]` and leave the | |
69 | non-option arguments in `argv[]`. | |
70 | `argc` is updated appropriately because of the assignment. | |
71 | + | |
37782920 | 72 | You can also pass NULL instead of a usage array as the fifth parameter of |
9ad7e6ea RS |
73 | parse_options(), to avoid displaying a help screen with usage info and |
74 | option list. This should only be done if necessary, e.g. to implement | |
75 | a limited parser for only a subset of the options that needs to be run | |
76 | before the full parser, which in turn shows the full help message. | |
77 | + | |
224712e5 SB |
78 | Flags are the bitwise-or of: |
79 | ||
80 | `PARSE_OPT_KEEP_DASHDASH`:: | |
6cf378f0 | 81 | Keep the `--` that usually separates options from |
224712e5 SB |
82 | non-option arguments. |
83 | ||
84 | `PARSE_OPT_STOP_AT_NON_OPTION`:: | |
85 | Usually the whole argument vector is massaged and reordered. | |
86 | Using this flag, processing is stopped at the first non-option | |
87 | argument. | |
88 | ||
9ad7e6ea RS |
89 | `PARSE_OPT_KEEP_ARGV0`:: |
90 | Keep the first argument, which contains the program name. It's | |
91 | removed from argv[] by default. | |
92 | ||
93 | `PARSE_OPT_KEEP_UNKNOWN`:: | |
94 | Keep unknown arguments instead of erroring out. This doesn't | |
95 | work for all combinations of arguments as users might expect | |
96 | it to do. E.g. if the first argument in `--unknown --known` | |
97 | takes a value (which we can't know), the second one is | |
98 | mistakenly interpreted as a known option. Similarly, if | |
99 | `PARSE_OPT_STOP_AT_NON_OPTION` is set, the second argument in | |
100 | `--unknown value` will be mistakenly interpreted as a | |
101 | non-option, not as a value belonging to the unknown option, | |
0d260f9a RS |
102 | the parser early. That's why parse_options() errors out if |
103 | both options are set. | |
9ad7e6ea RS |
104 | |
105 | `PARSE_OPT_NO_INTERNAL_HELP`:: | |
106 | By default, parse_options() handles `-h`, `--help` and | |
107 | `--help-all` internally, by showing a help screen. This option | |
108 | turns it off and allows one to add custom handlers for these | |
109 | options, or to just leave them unknown. | |
110 | ||
224712e5 SB |
111 | Data Structure |
112 | -------------- | |
113 | ||
114 | The main data structure is an array of the `option` struct, | |
115 | say `static struct option builtin_add_options[]`. | |
116 | There are some macros to easily define options: | |
117 | ||
118 | `OPT__ABBREV(&int_var)`:: | |
6cf378f0 | 119 | Add `--abbrev[=<n>]`. |
224712e5 | 120 | |
73e9da01 | 121 | `OPT__COLOR(&int_var, description)`:: |
6cf378f0 | 122 | Add `--color[=<when>]` and `--no-color`. |
73e9da01 | 123 | |
e21adb8c | 124 | `OPT__DRY_RUN(&int_var, description)`:: |
6cf378f0 | 125 | Add `-n, --dry-run`. |
224712e5 | 126 | |
76946b76 | 127 | `OPT__FORCE(&int_var, description)`:: |
6cf378f0 | 128 | Add `-f, --force`. |
76946b76 | 129 | |
d52ee6e6 | 130 | `OPT__QUIET(&int_var, description)`:: |
6cf378f0 | 131 | Add `-q, --quiet`. |
224712e5 | 132 | |
fd03881a | 133 | `OPT__VERBOSE(&int_var, description)`:: |
6cf378f0 | 134 | Add `-v, --verbose`. |
224712e5 SB |
135 | |
136 | `OPT_GROUP(description)`:: | |
137 | Start an option group. `description` is a short string that | |
138 | describes the group or an empty string. | |
139 | Start the description with an upper-case letter. | |
140 | ||
b04ba2bb JH |
141 | `OPT_BOOL(short, long, &int_var, description)`:: |
142 | Introduce a boolean option. `int_var` is set to one with | |
143 | `--option` and set to zero with `--no-option`. | |
144 | ||
145 | `OPT_COUNTUP(short, long, &int_var, description)`:: | |
146 | Introduce a count-up option. | |
e0070e8b PB |
147 | Each use of `--option` increments `int_var`, starting from zero |
148 | (even if initially negative), and `--no-option` resets it to | |
149 | zero. To determine if `--option` or `--no-option` was encountered at | |
150 | all, initialize `int_var` to a negative value, and if it is still | |
151 | negative after parse_options(), then neither `--option` nor | |
152 | `--no-option` was seen. | |
224712e5 SB |
153 | |
154 | `OPT_BIT(short, long, &int_var, description, mask)`:: | |
155 | Introduce a boolean option. | |
156 | If used, `int_var` is bitwise-ored with `mask`. | |
157 | ||
2f4b97f9 RS |
158 | `OPT_NEGBIT(short, long, &int_var, description, mask)`:: |
159 | Introduce a boolean option. | |
160 | If used, `int_var` is bitwise-anded with the inverted `mask`. | |
161 | ||
224712e5 | 162 | `OPT_SET_INT(short, long, &int_var, description, integer)`:: |
b04ba2bb JH |
163 | Introduce an integer option. |
164 | `int_var` is set to `integer` with `--option`, and | |
165 | reset to zero with `--no-option`. | |
224712e5 | 166 | |
224712e5 SB |
167 | `OPT_STRING(short, long, &str_var, arg_str, description)`:: |
168 | Introduce an option with string argument. | |
169 | The string argument is put into `str_var`. | |
170 | ||
4a687488 JK |
171 | `OPT_STRING_LIST(short, long, &struct string_list, arg_str, description)`:: |
172 | Introduce an option with string argument. | |
173 | The string argument is stored as an element in `string_list`. | |
174 | Use of `--no-option` will clear the list of preceding values. | |
175 | ||
224712e5 SB |
176 | `OPT_INTEGER(short, long, &int_var, description)`:: |
177 | Introduce an option with integer argument. | |
178 | The integer is put into `int_var`. | |
179 | ||
2a514ed8 CB |
180 | `OPT_MAGNITUDE(short, long, &unsigned_long_var, description)`:: |
181 | Introduce an option with a size argument. The argument must be a | |
182 | non-negative integer and may include a suffix of 'k', 'm' or 'g' to | |
183 | scale the provided value by 1024, 1024^2 or 1024^3 respectively. | |
184 | The scaled value is put into `unsigned_long_var`. | |
185 | ||
dddbad72 | 186 | `OPT_EXPIRY_DATE(short, long, ×tamp_t_var, description)`:: |
27ec394a | 187 | Introduce an option with expiry date argument, see `parse_expiry_date()`. |
dddbad72 | 188 | The timestamp is put into `timestamp_t_var`. |
27ec394a | 189 | |
224712e5 SB |
190 | `OPT_CALLBACK(short, long, &var, arg_str, description, func_ptr)`:: |
191 | Introduce an option with argument. | |
192 | The argument will be fed into the function given by `func_ptr` | |
193 | and the result will be put into `var`. | |
194 | See 'Option Callbacks' below for a more elaborate description. | |
195 | ||
df217ed6 SB |
196 | `OPT_FILENAME(short, long, &var, description)`:: |
197 | Introduce an option with a filename argument. | |
198 | The filename will be prefixed by passing the filename along with | |
199 | the prefix argument of `parse_options()` to `prefix_filename()`. | |
200 | ||
1a85b49b | 201 | `OPT_ARGUMENT(long, &int_var, description)`:: |
224712e5 | 202 | Introduce a long-option argument that will be kept in `argv[]`. |
1a85b49b JS |
203 | If this option was seen, `int_var` will be set to one (except |
204 | if a `NULL` pointer was passed). | |
224712e5 | 205 | |
e0319ff5 RS |
206 | `OPT_NUMBER_CALLBACK(&var, description, func_ptr)`:: |
207 | Recognize numerical options like -123 and feed the integer as | |
208 | if it was an argument to the function given by `func_ptr`. | |
209 | The result will be put into `var`. There can be only one such | |
210 | option definition. It cannot be negated and it takes no | |
211 | arguments. Short options that happen to be digits take | |
212 | precedence over it. | |
213 | ||
73e9da01 ML |
214 | `OPT_COLOR_FLAG(short, long, &int_var, description)`:: |
215 | Introduce an option that takes an optional argument that can | |
216 | have one of three values: "always", "never", or "auto". If the | |
217 | argument is not given, it defaults to "always". The `--no-` form | |
218 | works like `--long=never`; it cannot take an argument. If | |
219 | "always", set `int_var` to 1; if "never", set `int_var` to 0; if | |
220 | "auto", set `int_var` to 1 if stdout is a tty or a pager, | |
221 | 0 otherwise. | |
222 | ||
6acec038 RS |
223 | `OPT_NOOP_NOARG(short, long)`:: |
224 | Introduce an option that has no effect and takes no arguments. | |
225 | Use it to hide deprecated options that are still to be recognized | |
226 | and ignored silently. | |
227 | ||
6b3ee18d PT |
228 | `OPT_PASSTHRU(short, long, &char_var, arg_str, description, flags)`:: |
229 | Introduce an option that will be reconstructed into a char* string, | |
230 | which must be initialized to NULL. This is useful when you need to | |
231 | pass the command-line option to another command. Any previous value | |
232 | will be overwritten, so this should only be used for options where | |
233 | the last one specified on the command line wins. | |
234 | ||
ffad85c5 PT |
235 | `OPT_PASSTHRU_ARGV(short, long, &argv_array_var, arg_str, description, flags)`:: |
236 | Introduce an option where all instances of it on the command-line will | |
237 | be reconstructed into an argv_array. This is useful when you need to | |
238 | pass the command-line option, which can be specified multiple times, | |
239 | to another command. | |
240 | ||
c3f6b853 PB |
241 | `OPT_CMDMODE(short, long, &int_var, description, enum_val)`:: |
242 | Define an "operation mode" option, only one of which in the same | |
243 | group of "operating mode" options that share the same `int_var` | |
244 | can be given by the user. `enum_val` is set to `int_var` when the | |
245 | option is used, but an error is reported if other "operating mode" | |
246 | option has already set its value to the same `int_var`. | |
247 | ||
224712e5 SB |
248 | |
249 | The last element of the array must be `OPT_END()`. | |
250 | ||
251 | If not stated otherwise, interpret the arguments as follows: | |
252 | ||
253 | * `short` is a character for the short option | |
6cf378f0 | 254 | (e.g. `'e'` for `-e`, use `0` to omit), |
224712e5 SB |
255 | |
256 | * `long` is a string for the long option | |
6cf378f0 | 257 | (e.g. `"example"` for `--example`, use `NULL` to omit), |
224712e5 SB |
258 | |
259 | * `int_var` is an integer variable, | |
260 | ||
261 | * `str_var` is a string variable (`char *`), | |
262 | ||
263 | * `arg_str` is the string that is shown as argument | |
264 | (e.g. `"branch"` will result in `<branch>`). | |
265 | If set to `NULL`, three dots (`...`) will be displayed. | |
266 | ||
267 | * `description` is a short string to describe the effect of the option. | |
268 | It shall begin with a lower-case letter and a full stop (`.`) shall be | |
269 | omitted at the end. | |
270 | ||
271 | Option Callbacks | |
272 | ---------------- | |
273 | ||
274 | The function must be defined in this form: | |
275 | ||
276 | int func(const struct option *opt, const char *arg, int unset) | |
277 | ||
278 | The callback mechanism is as follows: | |
279 | ||
ca156cfc | 280 | * Inside `func`, the only interesting member of the structure |
6cf378f0 JK |
281 | given by `opt` is the void pointer `opt->value`. |
282 | `*opt->value` will be the value that is saved into `var`, if you | |
224712e5 | 283 | use `OPT_CALLBACK()`. |
6cf378f0 | 284 | For example, do `*(unsigned long *)opt->value = 42;` to get 42 |
224712e5 SB |
285 | into an `unsigned long` variable. |
286 | ||
287 | * Return value `0` indicates success and non-zero return | |
288 | value will invoke `usage_with_options()` and, thus, die. | |
289 | ||
290 | * If the user negates the option, `arg` is `NULL` and `unset` is 1. | |
291 | ||
292 | Sophisticated option parsing | |
293 | ---------------------------- | |
294 | ||
295 | If you need, for example, option callbacks with optional arguments | |
296 | or without arguments at all, or if you need other special cases, | |
297 | that are not handled by the macros above, you need to specify the | |
298 | members of the `option` structure manually. | |
299 | ||
300 | This is not covered in this document, but well documented | |
301 | in `parse-options.h` itself. | |
302 | ||
303 | Examples | |
304 | -------- | |
305 | ||
306 | See `test-parse-options.c` and | |
09b7e220 PH |
307 | `builtin/add.c`, |
308 | `builtin/clone.c`, | |
309 | `builtin/commit.c`, | |
310 | `builtin/fetch.c`, | |
311 | `builtin/fsck.c`, | |
312 | `builtin/rm.c` | |
224712e5 | 313 | for real-world examples. |