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1 | parse-options API |
2 | ================= | |
3 | ||
224712e5 SB |
4 | The parse-options API is used to parse and massage options in git |
5 | and to provide a usage help with consistent look. | |
530e741c | 6 | |
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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. | |
24 | 'Long options' begin with two dashes (`\--`) and some | |
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. | |
34 | `\--option=Arg` is sticked, `\--option Arg` is separate form. | |
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 | |
42 | `no-`, e.g. `\--no-abbrev` instead of `\--abbrev`. | |
43 | ||
44 | * Options and non-option arguments can clearly be separated using the `\--` | |
45 | option, e.g. `-a -b \--option \-- \--this-is-a-file` indicates that | |
46 | `\--this-is-a-file` must not be processed as an option. | |
47 | ||
48 | Steps to parse options | |
49 | ---------------------- | |
50 | ||
51 | . `#include "parse-options.h"` | |
52 | ||
53 | . define a NULL-terminated | |
54 | `static const char * const builtin_foo_usage[]` array | |
55 | containing alternative usage strings | |
56 | ||
57 | . define `builtin_foo_options` array as described below | |
58 | in section 'Data Structure'. | |
59 | ||
60 | . in `cmd_foo(int argc, const char **argv, const char *prefix)` | |
61 | call | |
62 | ||
37782920 | 63 | argc = parse_options(argc, argv, prefix, builtin_foo_options, builtin_foo_usage, flags); |
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64 | + |
65 | `parse_options()` will filter out the processed options of `argv[]` and leave the | |
66 | non-option arguments in `argv[]`. | |
67 | `argc` is updated appropriately because of the assignment. | |
68 | + | |
37782920 | 69 | You can also pass NULL instead of a usage array as the fifth parameter of |
9ad7e6ea RS |
70 | parse_options(), to avoid displaying a help screen with usage info and |
71 | option list. This should only be done if necessary, e.g. to implement | |
72 | a limited parser for only a subset of the options that needs to be run | |
73 | before the full parser, which in turn shows the full help message. | |
74 | + | |
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75 | Flags are the bitwise-or of: |
76 | ||
77 | `PARSE_OPT_KEEP_DASHDASH`:: | |
78 | Keep the `\--` that usually separates options from | |
79 | non-option arguments. | |
80 | ||
81 | `PARSE_OPT_STOP_AT_NON_OPTION`:: | |
82 | Usually the whole argument vector is massaged and reordered. | |
83 | Using this flag, processing is stopped at the first non-option | |
84 | argument. | |
85 | ||
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86 | `PARSE_OPT_KEEP_ARGV0`:: |
87 | Keep the first argument, which contains the program name. It's | |
88 | removed from argv[] by default. | |
89 | ||
90 | `PARSE_OPT_KEEP_UNKNOWN`:: | |
91 | Keep unknown arguments instead of erroring out. This doesn't | |
92 | work for all combinations of arguments as users might expect | |
93 | it to do. E.g. if the first argument in `--unknown --known` | |
94 | takes a value (which we can't know), the second one is | |
95 | mistakenly interpreted as a known option. Similarly, if | |
96 | `PARSE_OPT_STOP_AT_NON_OPTION` is set, the second argument in | |
97 | `--unknown value` will be mistakenly interpreted as a | |
98 | non-option, not as a value belonging to the unknown option, | |
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99 | the parser early. That's why parse_options() errors out if |
100 | both options are set. | |
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101 | |
102 | `PARSE_OPT_NO_INTERNAL_HELP`:: | |
103 | By default, parse_options() handles `-h`, `--help` and | |
104 | `--help-all` internally, by showing a help screen. This option | |
105 | turns it off and allows one to add custom handlers for these | |
106 | options, or to just leave them unknown. | |
107 | ||
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108 | Data Structure |
109 | -------------- | |
110 | ||
111 | The main data structure is an array of the `option` struct, | |
112 | say `static struct option builtin_add_options[]`. | |
113 | There are some macros to easily define options: | |
114 | ||
115 | `OPT__ABBREV(&int_var)`:: | |
116 | Add `\--abbrev[=<n>]`. | |
117 | ||
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118 | `OPT__COLOR(&int_var, description)`:: |
119 | Add `\--color[=<when>]` and `--no-color`. | |
120 | ||
e21adb8c | 121 | `OPT__DRY_RUN(&int_var, description)`:: |
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122 | Add `-n, \--dry-run`. |
123 | ||
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124 | `OPT__FORCE(&int_var, description)`:: |
125 | Add `-f, \--force`. | |
126 | ||
d52ee6e6 | 127 | `OPT__QUIET(&int_var, description)`:: |
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128 | Add `-q, \--quiet`. |
129 | ||
fd03881a | 130 | `OPT__VERBOSE(&int_var, description)`:: |
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131 | Add `-v, \--verbose`. |
132 | ||
133 | `OPT_GROUP(description)`:: | |
134 | Start an option group. `description` is a short string that | |
135 | describes the group or an empty string. | |
136 | Start the description with an upper-case letter. | |
137 | ||
138 | `OPT_BOOLEAN(short, long, &int_var, description)`:: | |
139 | Introduce a boolean option. | |
140 | `int_var` is incremented on each use. | |
141 | ||
142 | `OPT_BIT(short, long, &int_var, description, mask)`:: | |
143 | Introduce a boolean option. | |
144 | If used, `int_var` is bitwise-ored with `mask`. | |
145 | ||
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146 | `OPT_NEGBIT(short, long, &int_var, description, mask)`:: |
147 | Introduce a boolean option. | |
148 | If used, `int_var` is bitwise-anded with the inverted `mask`. | |
149 | ||
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150 | `OPT_SET_INT(short, long, &int_var, description, integer)`:: |
151 | Introduce a boolean option. | |
152 | If used, set `int_var` to `integer`. | |
153 | ||
154 | `OPT_SET_PTR(short, long, &ptr_var, description, ptr)`:: | |
155 | Introduce a boolean option. | |
156 | If used, set `ptr_var` to `ptr`. | |
157 | ||
158 | `OPT_STRING(short, long, &str_var, arg_str, description)`:: | |
159 | Introduce an option with string argument. | |
160 | The string argument is put into `str_var`. | |
161 | ||
162 | `OPT_INTEGER(short, long, &int_var, description)`:: | |
163 | Introduce an option with integer argument. | |
164 | The integer is put into `int_var`. | |
165 | ||
166 | `OPT_DATE(short, long, &int_var, description)`:: | |
167 | Introduce an option with date argument, see `approxidate()`. | |
168 | The timestamp is put into `int_var`. | |
169 | ||
170 | `OPT_CALLBACK(short, long, &var, arg_str, description, func_ptr)`:: | |
171 | Introduce an option with argument. | |
172 | The argument will be fed into the function given by `func_ptr` | |
173 | and the result will be put into `var`. | |
174 | See 'Option Callbacks' below for a more elaborate description. | |
175 | ||
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176 | `OPT_FILENAME(short, long, &var, description)`:: |
177 | Introduce an option with a filename argument. | |
178 | The filename will be prefixed by passing the filename along with | |
179 | the prefix argument of `parse_options()` to `prefix_filename()`. | |
180 | ||
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181 | `OPT_ARGUMENT(long, description)`:: |
182 | Introduce a long-option argument that will be kept in `argv[]`. | |
183 | ||
e0319ff5 RS |
184 | `OPT_NUMBER_CALLBACK(&var, description, func_ptr)`:: |
185 | Recognize numerical options like -123 and feed the integer as | |
186 | if it was an argument to the function given by `func_ptr`. | |
187 | The result will be put into `var`. There can be only one such | |
188 | option definition. It cannot be negated and it takes no | |
189 | arguments. Short options that happen to be digits take | |
190 | precedence over it. | |
191 | ||
73e9da01 ML |
192 | `OPT_COLOR_FLAG(short, long, &int_var, description)`:: |
193 | Introduce an option that takes an optional argument that can | |
194 | have one of three values: "always", "never", or "auto". If the | |
195 | argument is not given, it defaults to "always". The `--no-` form | |
196 | works like `--long=never`; it cannot take an argument. If | |
197 | "always", set `int_var` to 1; if "never", set `int_var` to 0; if | |
198 | "auto", set `int_var` to 1 if stdout is a tty or a pager, | |
199 | 0 otherwise. | |
200 | ||
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201 | |
202 | The last element of the array must be `OPT_END()`. | |
203 | ||
204 | If not stated otherwise, interpret the arguments as follows: | |
205 | ||
206 | * `short` is a character for the short option | |
6dcca4d0 | 207 | (e.g. `{apostrophe}e{apostrophe}` for `-e`, use `0` to omit), |
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208 | |
209 | * `long` is a string for the long option | |
210 | (e.g. `"example"` for `\--example`, use `NULL` to omit), | |
211 | ||
212 | * `int_var` is an integer variable, | |
213 | ||
214 | * `str_var` is a string variable (`char *`), | |
215 | ||
216 | * `arg_str` is the string that is shown as argument | |
217 | (e.g. `"branch"` will result in `<branch>`). | |
218 | If set to `NULL`, three dots (`...`) will be displayed. | |
219 | ||
220 | * `description` is a short string to describe the effect of the option. | |
221 | It shall begin with a lower-case letter and a full stop (`.`) shall be | |
222 | omitted at the end. | |
223 | ||
224 | Option Callbacks | |
225 | ---------------- | |
226 | ||
227 | The function must be defined in this form: | |
228 | ||
229 | int func(const struct option *opt, const char *arg, int unset) | |
230 | ||
231 | The callback mechanism is as follows: | |
232 | ||
ca156cfc | 233 | * Inside `func`, the only interesting member of the structure |
6dcca4d0 JN |
234 | given by `opt` is the void pointer `opt\->value`. |
235 | `\*opt\->value` will be the value that is saved into `var`, if you | |
224712e5 | 236 | use `OPT_CALLBACK()`. |
6dcca4d0 | 237 | For example, do `*(unsigned long *)opt\->value = 42;` to get 42 |
224712e5 SB |
238 | into an `unsigned long` variable. |
239 | ||
240 | * Return value `0` indicates success and non-zero return | |
241 | value will invoke `usage_with_options()` and, thus, die. | |
242 | ||
243 | * If the user negates the option, `arg` is `NULL` and `unset` is 1. | |
244 | ||
245 | Sophisticated option parsing | |
246 | ---------------------------- | |
247 | ||
248 | If you need, for example, option callbacks with optional arguments | |
249 | or without arguments at all, or if you need other special cases, | |
250 | that are not handled by the macros above, you need to specify the | |
251 | members of the `option` structure manually. | |
252 | ||
253 | This is not covered in this document, but well documented | |
254 | in `parse-options.h` itself. | |
255 | ||
256 | Examples | |
257 | -------- | |
258 | ||
259 | See `test-parse-options.c` and | |
260 | `builtin-add.c`, | |
261 | `builtin-clone.c`, | |
262 | `builtin-commit.c`, | |
263 | `builtin-fetch.c`, | |
264 | `builtin-fsck.c`, | |
265 | `builtin-rm.c` | |
266 | for real-world examples. |