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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 | ||
32 | * 'sticked' and 'separate form' of options with arguments. | |
33 | `-oArg` is sticked, `-o Arg` is separate form. | |
6cf378f0 | 34 | `--option=Arg` is sticked, `--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. |
224712e5 | 44 | |
6cf378f0 JK |
45 | * Options and non-option arguments can clearly be separated using the `--` |
46 | option, e.g. `-a -b --option -- --this-is-a-file` indicates that | |
47 | `--this-is-a-file` must not be processed as an option. | |
224712e5 SB |
48 | |
49 | Steps to parse options | |
50 | ---------------------- | |
51 | ||
52 | . `#include "parse-options.h"` | |
53 | ||
54 | . define a NULL-terminated | |
55 | `static const char * const builtin_foo_usage[]` array | |
56 | containing alternative usage strings | |
57 | ||
58 | . define `builtin_foo_options` array as described below | |
59 | in section 'Data Structure'. | |
60 | ||
61 | . in `cmd_foo(int argc, const char **argv, const char *prefix)` | |
62 | call | |
63 | ||
37782920 | 64 | argc = parse_options(argc, argv, prefix, builtin_foo_options, builtin_foo_usage, flags); |
224712e5 SB |
65 | + |
66 | `parse_options()` will filter out the processed options of `argv[]` and leave the | |
67 | non-option arguments in `argv[]`. | |
68 | `argc` is updated appropriately because of the assignment. | |
69 | + | |
37782920 | 70 | You can also pass NULL instead of a usage array as the fifth parameter of |
9ad7e6ea RS |
71 | parse_options(), to avoid displaying a help screen with usage info and |
72 | option list. This should only be done if necessary, e.g. to implement | |
73 | a limited parser for only a subset of the options that needs to be run | |
74 | before the full parser, which in turn shows the full help message. | |
75 | + | |
224712e5 SB |
76 | Flags are the bitwise-or of: |
77 | ||
78 | `PARSE_OPT_KEEP_DASHDASH`:: | |
6cf378f0 | 79 | Keep the `--` that usually separates options from |
224712e5 SB |
80 | non-option arguments. |
81 | ||
82 | `PARSE_OPT_STOP_AT_NON_OPTION`:: | |
83 | Usually the whole argument vector is massaged and reordered. | |
84 | Using this flag, processing is stopped at the first non-option | |
85 | argument. | |
86 | ||
9ad7e6ea RS |
87 | `PARSE_OPT_KEEP_ARGV0`:: |
88 | Keep the first argument, which contains the program name. It's | |
89 | removed from argv[] by default. | |
90 | ||
91 | `PARSE_OPT_KEEP_UNKNOWN`:: | |
92 | Keep unknown arguments instead of erroring out. This doesn't | |
93 | work for all combinations of arguments as users might expect | |
94 | it to do. E.g. if the first argument in `--unknown --known` | |
95 | takes a value (which we can't know), the second one is | |
96 | mistakenly interpreted as a known option. Similarly, if | |
97 | `PARSE_OPT_STOP_AT_NON_OPTION` is set, the second argument in | |
98 | `--unknown value` will be mistakenly interpreted as a | |
99 | non-option, not as a value belonging to the unknown option, | |
0d260f9a RS |
100 | the parser early. That's why parse_options() errors out if |
101 | both options are set. | |
9ad7e6ea RS |
102 | |
103 | `PARSE_OPT_NO_INTERNAL_HELP`:: | |
104 | By default, parse_options() handles `-h`, `--help` and | |
105 | `--help-all` internally, by showing a help screen. This option | |
106 | turns it off and allows one to add custom handlers for these | |
107 | options, or to just leave them unknown. | |
108 | ||
224712e5 SB |
109 | Data Structure |
110 | -------------- | |
111 | ||
112 | The main data structure is an array of the `option` struct, | |
113 | say `static struct option builtin_add_options[]`. | |
114 | There are some macros to easily define options: | |
115 | ||
116 | `OPT__ABBREV(&int_var)`:: | |
6cf378f0 | 117 | Add `--abbrev[=<n>]`. |
224712e5 | 118 | |
73e9da01 | 119 | `OPT__COLOR(&int_var, description)`:: |
6cf378f0 | 120 | Add `--color[=<when>]` and `--no-color`. |
73e9da01 | 121 | |
e21adb8c | 122 | `OPT__DRY_RUN(&int_var, description)`:: |
6cf378f0 | 123 | Add `-n, --dry-run`. |
224712e5 | 124 | |
76946b76 | 125 | `OPT__FORCE(&int_var, description)`:: |
6cf378f0 | 126 | Add `-f, --force`. |
76946b76 | 127 | |
d52ee6e6 | 128 | `OPT__QUIET(&int_var, description)`:: |
6cf378f0 | 129 | Add `-q, --quiet`. |
224712e5 | 130 | |
fd03881a | 131 | `OPT__VERBOSE(&int_var, description)`:: |
6cf378f0 | 132 | Add `-v, --verbose`. |
224712e5 SB |
133 | |
134 | `OPT_GROUP(description)`:: | |
135 | Start an option group. `description` is a short string that | |
136 | describes the group or an empty string. | |
137 | Start the description with an upper-case letter. | |
138 | ||
b04ba2bb JH |
139 | `OPT_BOOL(short, long, &int_var, description)`:: |
140 | Introduce a boolean option. `int_var` is set to one with | |
141 | `--option` and set to zero with `--no-option`. | |
142 | ||
143 | `OPT_COUNTUP(short, long, &int_var, description)`:: | |
144 | Introduce a count-up option. | |
145 | `int_var` is incremented on each use of `--option`, and | |
146 | reset to zero with `--no-option`. | |
224712e5 SB |
147 | |
148 | `OPT_BIT(short, long, &int_var, description, mask)`:: | |
149 | Introduce a boolean option. | |
150 | If used, `int_var` is bitwise-ored with `mask`. | |
151 | ||
2f4b97f9 RS |
152 | `OPT_NEGBIT(short, long, &int_var, description, mask)`:: |
153 | Introduce a boolean option. | |
154 | If used, `int_var` is bitwise-anded with the inverted `mask`. | |
155 | ||
224712e5 | 156 | `OPT_SET_INT(short, long, &int_var, description, integer)`:: |
b04ba2bb JH |
157 | Introduce an integer option. |
158 | `int_var` is set to `integer` with `--option`, and | |
159 | reset to zero with `--no-option`. | |
224712e5 SB |
160 | |
161 | `OPT_SET_PTR(short, long, &ptr_var, description, ptr)`:: | |
162 | Introduce a boolean option. | |
163 | If used, set `ptr_var` to `ptr`. | |
164 | ||
165 | `OPT_STRING(short, long, &str_var, arg_str, description)`:: | |
166 | Introduce an option with string argument. | |
167 | The string argument is put into `str_var`. | |
168 | ||
169 | `OPT_INTEGER(short, long, &int_var, description)`:: | |
170 | Introduce an option with integer argument. | |
171 | The integer is put into `int_var`. | |
172 | ||
173 | `OPT_DATE(short, long, &int_var, description)`:: | |
174 | Introduce an option with date argument, see `approxidate()`. | |
175 | The timestamp is put into `int_var`. | |
176 | ||
177 | `OPT_CALLBACK(short, long, &var, arg_str, description, func_ptr)`:: | |
178 | Introduce an option with argument. | |
179 | The argument will be fed into the function given by `func_ptr` | |
180 | and the result will be put into `var`. | |
181 | See 'Option Callbacks' below for a more elaborate description. | |
182 | ||
df217ed6 SB |
183 | `OPT_FILENAME(short, long, &var, description)`:: |
184 | Introduce an option with a filename argument. | |
185 | The filename will be prefixed by passing the filename along with | |
186 | the prefix argument of `parse_options()` to `prefix_filename()`. | |
187 | ||
224712e5 SB |
188 | `OPT_ARGUMENT(long, description)`:: |
189 | Introduce a long-option argument that will be kept in `argv[]`. | |
190 | ||
e0319ff5 RS |
191 | `OPT_NUMBER_CALLBACK(&var, description, func_ptr)`:: |
192 | Recognize numerical options like -123 and feed the integer as | |
193 | if it was an argument to the function given by `func_ptr`. | |
194 | The result will be put into `var`. There can be only one such | |
195 | option definition. It cannot be negated and it takes no | |
196 | arguments. Short options that happen to be digits take | |
197 | precedence over it. | |
198 | ||
73e9da01 ML |
199 | `OPT_COLOR_FLAG(short, long, &int_var, description)`:: |
200 | Introduce an option that takes an optional argument that can | |
201 | have one of three values: "always", "never", or "auto". If the | |
202 | argument is not given, it defaults to "always". The `--no-` form | |
203 | works like `--long=never`; it cannot take an argument. If | |
204 | "always", set `int_var` to 1; if "never", set `int_var` to 0; if | |
205 | "auto", set `int_var` to 1 if stdout is a tty or a pager, | |
206 | 0 otherwise. | |
207 | ||
6acec038 RS |
208 | `OPT_NOOP_NOARG(short, long)`:: |
209 | Introduce an option that has no effect and takes no arguments. | |
210 | Use it to hide deprecated options that are still to be recognized | |
211 | and ignored silently. | |
212 | ||
224712e5 SB |
213 | |
214 | The last element of the array must be `OPT_END()`. | |
215 | ||
216 | If not stated otherwise, interpret the arguments as follows: | |
217 | ||
218 | * `short` is a character for the short option | |
6cf378f0 | 219 | (e.g. `'e'` for `-e`, use `0` to omit), |
224712e5 SB |
220 | |
221 | * `long` is a string for the long option | |
6cf378f0 | 222 | (e.g. `"example"` for `--example`, use `NULL` to omit), |
224712e5 SB |
223 | |
224 | * `int_var` is an integer variable, | |
225 | ||
226 | * `str_var` is a string variable (`char *`), | |
227 | ||
228 | * `arg_str` is the string that is shown as argument | |
229 | (e.g. `"branch"` will result in `<branch>`). | |
230 | If set to `NULL`, three dots (`...`) will be displayed. | |
231 | ||
232 | * `description` is a short string to describe the effect of the option. | |
233 | It shall begin with a lower-case letter and a full stop (`.`) shall be | |
234 | omitted at the end. | |
235 | ||
236 | Option Callbacks | |
237 | ---------------- | |
238 | ||
239 | The function must be defined in this form: | |
240 | ||
241 | int func(const struct option *opt, const char *arg, int unset) | |
242 | ||
243 | The callback mechanism is as follows: | |
244 | ||
ca156cfc | 245 | * Inside `func`, the only interesting member of the structure |
6cf378f0 JK |
246 | given by `opt` is the void pointer `opt->value`. |
247 | `*opt->value` will be the value that is saved into `var`, if you | |
224712e5 | 248 | use `OPT_CALLBACK()`. |
6cf378f0 | 249 | For example, do `*(unsigned long *)opt->value = 42;` to get 42 |
224712e5 SB |
250 | into an `unsigned long` variable. |
251 | ||
252 | * Return value `0` indicates success and non-zero return | |
253 | value will invoke `usage_with_options()` and, thus, die. | |
254 | ||
255 | * If the user negates the option, `arg` is `NULL` and `unset` is 1. | |
256 | ||
257 | Sophisticated option parsing | |
258 | ---------------------------- | |
259 | ||
260 | If you need, for example, option callbacks with optional arguments | |
261 | or without arguments at all, or if you need other special cases, | |
262 | that are not handled by the macros above, you need to specify the | |
263 | members of the `option` structure manually. | |
264 | ||
265 | This is not covered in this document, but well documented | |
266 | in `parse-options.h` itself. | |
267 | ||
268 | Examples | |
269 | -------- | |
270 | ||
271 | See `test-parse-options.c` and | |
272 | `builtin-add.c`, | |
273 | `builtin-clone.c`, | |
274 | `builtin-commit.c`, | |
275 | `builtin-fetch.c`, | |
276 | `builtin-fsck.c`, | |
277 | `builtin-rm.c` | |
278 | for real-world examples. |