4 The parse-options API is used to parse and massage options in Git
5 and to provide a usage help with consistent look.
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.
15 * There are basically three types of options:
17 options with (mandatory) 'arguments' and
18 options with 'optional arguments'
19 (i.e. a boolean option that can be adjusted).
21 * There are basically two forms of options:
22 'Short options' consist of one dash (`-`) and one alphanumeric
24 'Long options' begin with two dashes (`--`) and some
25 alphanumeric characters.
27 * Options are case-sensitive.
28 Please define 'lower-case long options' only.
30 The parse-options API allows:
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.
36 * Long options may be 'abbreviated', as long as the abbreviation
39 * Short options may be bundled, e.g. `-a -b` can be specified as `-ab`.
41 * Boolean long options can be 'negated' (or 'unset') by prepending
42 `no-`, e.g. `--no-abbrev` instead of `--abbrev`. Conversely,
43 options that begin with `no-` can be 'negated' by removing it.
44 Other long options can be unset (e.g., set string to NULL, set
45 integer to 0) by prepending `no-`.
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.
51 Steps to parse options
52 ----------------------
54 . `#include "parse-options.h"`
56 . define a NULL-terminated
57 `static const char * const builtin_foo_usage[]` array
58 containing alternative usage strings
60 . define `builtin_foo_options` array as described below
61 in section 'Data Structure'.
63 . in `cmd_foo(int argc, const char **argv, const char *prefix)`
66 argc = parse_options(argc, argv, prefix, builtin_foo_options, builtin_foo_usage, flags);
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.
72 You can also pass NULL instead of a usage array as the fifth parameter of
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.
78 Flags are the bitwise-or of:
80 `PARSE_OPT_KEEP_DASHDASH`::
81 Keep the `--` that usually separates options from
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
89 `PARSE_OPT_KEEP_ARGV0`::
90 Keep the first argument, which contains the program name. It's
91 removed from argv[] by default.
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,
102 the parser early. That's why parse_options() errors out if
103 both options are set.
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.
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:
118 `OPT__ABBREV(&int_var)`::
119 Add `--abbrev[=<n>]`.
121 `OPT__COLOR(&int_var, description)`::
122 Add `--color[=<when>]` and `--no-color`.
124 `OPT__DRY_RUN(&int_var, description)`::
127 `OPT__FORCE(&int_var, description)`::
130 `OPT__QUIET(&int_var, description)`::
133 `OPT__VERBOSE(&int_var, description)`::
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.
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`.
145 `OPT_COUNTUP(short, long, &int_var, description)`::
146 Introduce a count-up option.
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.
154 `OPT_BIT(short, long, &int_var, description, mask)`::
155 Introduce a boolean option.
156 If used, `int_var` is bitwise-ored with `mask`.
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`.
162 `OPT_SET_INT(short, long, &int_var, description, integer)`::
163 Introduce an integer option.
164 `int_var` is set to `integer` with `--option`, and
165 reset to zero with `--no-option`.
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`.
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.
176 `OPT_INTEGER(short, long, &int_var, description)`::
177 Introduce an option with integer argument.
178 The integer is put into `int_var`.
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`.
186 `OPT_EXPIRY_DATE(short, long, ×tamp_t_var, description)`::
187 Introduce an option with expiry date argument, see `parse_expiry_date()`.
188 The timestamp is put into `timestamp_t_var`.
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.
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()`.
201 `OPT_ARGUMENT(long, description)`::
202 Introduce a long-option argument that will be kept in `argv[]`.
204 `OPT_NUMBER_CALLBACK(&var, description, func_ptr)`::
205 Recognize numerical options like -123 and feed the integer as
206 if it was an argument to the function given by `func_ptr`.
207 The result will be put into `var`. There can be only one such
208 option definition. It cannot be negated and it takes no
209 arguments. Short options that happen to be digits take
212 `OPT_COLOR_FLAG(short, long, &int_var, description)`::
213 Introduce an option that takes an optional argument that can
214 have one of three values: "always", "never", or "auto". If the
215 argument is not given, it defaults to "always". The `--no-` form
216 works like `--long=never`; it cannot take an argument. If
217 "always", set `int_var` to 1; if "never", set `int_var` to 0; if
218 "auto", set `int_var` to 1 if stdout is a tty or a pager,
221 `OPT_NOOP_NOARG(short, long)`::
222 Introduce an option that has no effect and takes no arguments.
223 Use it to hide deprecated options that are still to be recognized
224 and ignored silently.
226 `OPT_PASSTHRU(short, long, &char_var, arg_str, description, flags)`::
227 Introduce an option that will be reconstructed into a char* string,
228 which must be initialized to NULL. This is useful when you need to
229 pass the command-line option to another command. Any previous value
230 will be overwritten, so this should only be used for options where
231 the last one specified on the command line wins.
233 `OPT_PASSTHRU_ARGV(short, long, &argv_array_var, arg_str, description, flags)`::
234 Introduce an option where all instances of it on the command-line will
235 be reconstructed into an argv_array. This is useful when you need to
236 pass the command-line option, which can be specified multiple times,
239 `OPT_CMDMODE(short, long, &int_var, description, enum_val)`::
240 Define an "operation mode" option, only one of which in the same
241 group of "operating mode" options that share the same `int_var`
242 can be given by the user. `enum_val` is set to `int_var` when the
243 option is used, but an error is reported if other "operating mode"
244 option has already set its value to the same `int_var`.
247 The last element of the array must be `OPT_END()`.
249 If not stated otherwise, interpret the arguments as follows:
251 * `short` is a character for the short option
252 (e.g. `'e'` for `-e`, use `0` to omit),
254 * `long` is a string for the long option
255 (e.g. `"example"` for `--example`, use `NULL` to omit),
257 * `int_var` is an integer variable,
259 * `str_var` is a string variable (`char *`),
261 * `arg_str` is the string that is shown as argument
262 (e.g. `"branch"` will result in `<branch>`).
263 If set to `NULL`, three dots (`...`) will be displayed.
265 * `description` is a short string to describe the effect of the option.
266 It shall begin with a lower-case letter and a full stop (`.`) shall be
272 The function must be defined in this form:
274 int func(const struct option *opt, const char *arg, int unset)
276 The callback mechanism is as follows:
278 * Inside `func`, the only interesting member of the structure
279 given by `opt` is the void pointer `opt->value`.
280 `*opt->value` will be the value that is saved into `var`, if you
281 use `OPT_CALLBACK()`.
282 For example, do `*(unsigned long *)opt->value = 42;` to get 42
283 into an `unsigned long` variable.
285 * Return value `0` indicates success and non-zero return
286 value will invoke `usage_with_options()` and, thus, die.
288 * If the user negates the option, `arg` is `NULL` and `unset` is 1.
290 Sophisticated option parsing
291 ----------------------------
293 If you need, for example, option callbacks with optional arguments
294 or without arguments at all, or if you need other special cases,
295 that are not handled by the macros above, you need to specify the
296 members of the `option` structure manually.
298 This is not covered in this document, but well documented
299 in `parse-options.h` itself.
304 See `test-parse-options.c` and
311 for real-world examples.