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 `int_var` is incremented on each use of `--option`, and
148 reset to zero with `--no-option`.
150 `OPT_BIT(short, long, &int_var, description, mask)`::
151 Introduce a boolean option.
152 If used, `int_var` is bitwise-ored with `mask`.
154 `OPT_NEGBIT(short, long, &int_var, description, mask)`::
155 Introduce a boolean option.
156 If used, `int_var` is bitwise-anded with the inverted `mask`.
158 `OPT_SET_INT(short, long, &int_var, description, integer)`::
159 Introduce an integer option.
160 `int_var` is set to `integer` with `--option`, and
161 reset to zero with `--no-option`.
163 `OPT_STRING(short, long, &str_var, arg_str, description)`::
164 Introduce an option with string argument.
165 The string argument is put into `str_var`.
167 `OPT_INTEGER(short, long, &int_var, description)`::
168 Introduce an option with integer argument.
169 The integer is put into `int_var`.
171 `OPT_DATE(short, long, &int_var, description)`::
172 Introduce an option with date argument, see `approxidate()`.
173 The timestamp is put into `int_var`.
175 `OPT_EXPIRY_DATE(short, long, &int_var, description)`::
176 Introduce an option with expiry date argument, see `parse_expiry_date()`.
177 The timestamp is put into `int_var`.
179 `OPT_CALLBACK(short, long, &var, arg_str, description, func_ptr)`::
180 Introduce an option with argument.
181 The argument will be fed into the function given by `func_ptr`
182 and the result will be put into `var`.
183 See 'Option Callbacks' below for a more elaborate description.
185 `OPT_FILENAME(short, long, &var, description)`::
186 Introduce an option with a filename argument.
187 The filename will be prefixed by passing the filename along with
188 the prefix argument of `parse_options()` to `prefix_filename()`.
190 `OPT_ARGUMENT(long, description)`::
191 Introduce a long-option argument that will be kept in `argv[]`.
193 `OPT_NUMBER_CALLBACK(&var, description, func_ptr)`::
194 Recognize numerical options like -123 and feed the integer as
195 if it was an argument to the function given by `func_ptr`.
196 The result will be put into `var`. There can be only one such
197 option definition. It cannot be negated and it takes no
198 arguments. Short options that happen to be digits take
201 `OPT_COLOR_FLAG(short, long, &int_var, description)`::
202 Introduce an option that takes an optional argument that can
203 have one of three values: "always", "never", or "auto". If the
204 argument is not given, it defaults to "always". The `--no-` form
205 works like `--long=never`; it cannot take an argument. If
206 "always", set `int_var` to 1; if "never", set `int_var` to 0; if
207 "auto", set `int_var` to 1 if stdout is a tty or a pager,
210 `OPT_NOOP_NOARG(short, long)`::
211 Introduce an option that has no effect and takes no arguments.
212 Use it to hide deprecated options that are still to be recognized
213 and ignored silently.
215 `OPT_PASSTHRU(short, long, &char_var, arg_str, description, flags)`::
216 Introduce an option that will be reconstructed into a char* string,
217 which must be initialized to NULL. This is useful when you need to
218 pass the command-line option to another command. Any previous value
219 will be overwritten, so this should only be used for options where
220 the last one specified on the command line wins.
222 `OPT_PASSTHRU_ARGV(short, long, &argv_array_var, arg_str, description, flags)`::
223 Introduce an option where all instances of it on the command-line will
224 be reconstructed into an argv_array. This is useful when you need to
225 pass the command-line option, which can be specified multiple times,
229 The last element of the array must be `OPT_END()`.
231 If not stated otherwise, interpret the arguments as follows:
233 * `short` is a character for the short option
234 (e.g. `'e'` for `-e`, use `0` to omit),
236 * `long` is a string for the long option
237 (e.g. `"example"` for `--example`, use `NULL` to omit),
239 * `int_var` is an integer variable,
241 * `str_var` is a string variable (`char *`),
243 * `arg_str` is the string that is shown as argument
244 (e.g. `"branch"` will result in `<branch>`).
245 If set to `NULL`, three dots (`...`) will be displayed.
247 * `description` is a short string to describe the effect of the option.
248 It shall begin with a lower-case letter and a full stop (`.`) shall be
254 The function must be defined in this form:
256 int func(const struct option *opt, const char *arg, int unset)
258 The callback mechanism is as follows:
260 * Inside `func`, the only interesting member of the structure
261 given by `opt` is the void pointer `opt->value`.
262 `*opt->value` will be the value that is saved into `var`, if you
263 use `OPT_CALLBACK()`.
264 For example, do `*(unsigned long *)opt->value = 42;` to get 42
265 into an `unsigned long` variable.
267 * Return value `0` indicates success and non-zero return
268 value will invoke `usage_with_options()` and, thus, die.
270 * If the user negates the option, `arg` is `NULL` and `unset` is 1.
272 Sophisticated option parsing
273 ----------------------------
275 If you need, for example, option callbacks with optional arguments
276 or without arguments at all, or if you need other special cases,
277 that are not handled by the macros above, you need to specify the
278 members of the `option` structure manually.
280 This is not covered in this document, but well documented
281 in `parse-options.h` itself.
286 See `test-parse-options.c` and
293 for real-world examples.