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 * '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.
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`.
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.
48 Steps to parse options
49 ----------------------
51 . `#include "parse-options.h"`
53 . define a NULL-terminated
54 `static const char * const builtin_foo_usage[]` array
55 containing alternative usage strings
57 . define `builtin_foo_options` array as described below
58 in section 'Data Structure'.
60 . in `cmd_foo(int argc, const char **argv, const char *prefix)`
63 argc = parse_options(argc, argv, builtin_foo_options, builtin_foo_usage, flags);
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.
69 You can also pass NULL instead of a usage array as fourth parameter of
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.
75 Flags are the bitwise-or of:
77 `PARSE_OPT_KEEP_DASHDASH`::
78 Keep the `\--` that usually separates options from
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
86 `PARSE_OPT_KEEP_ARGV0`::
87 Keep the first argument, which contains the program name. It's
88 removed from argv[] by default.
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,
99 stopping the parser early.
101 `PARSE_OPT_NO_INTERNAL_HELP`::
102 By default, parse_options() handles `-h`, `--help` and
103 `--help-all` internally, by showing a help screen. This option
104 turns it off and allows one to add custom handlers for these
105 options, or to just leave them unknown.
110 The main data structure is an array of the `option` struct,
111 say `static struct option builtin_add_options[]`.
112 There are some macros to easily define options:
114 `OPT__ABBREV(&int_var)`::
115 Add `\--abbrev[=<n>]`.
117 `OPT__DRY_RUN(&int_var)`::
118 Add `-n, \--dry-run`.
120 `OPT__QUIET(&int_var)`::
123 `OPT__VERBOSE(&int_var)`::
124 Add `-v, \--verbose`.
126 `OPT_GROUP(description)`::
127 Start an option group. `description` is a short string that
128 describes the group or an empty string.
129 Start the description with an upper-case letter.
131 `OPT_BOOLEAN(short, long, &int_var, description)`::
132 Introduce a boolean option.
133 `int_var` is incremented on each use.
135 `OPT_BIT(short, long, &int_var, description, mask)`::
136 Introduce a boolean option.
137 If used, `int_var` is bitwise-ored with `mask`.
139 `OPT_SET_INT(short, long, &int_var, description, integer)`::
140 Introduce a boolean option.
141 If used, set `int_var` to `integer`.
143 `OPT_SET_PTR(short, long, &ptr_var, description, ptr)`::
144 Introduce a boolean option.
145 If used, set `ptr_var` to `ptr`.
147 `OPT_STRING(short, long, &str_var, arg_str, description)`::
148 Introduce an option with string argument.
149 The string argument is put into `str_var`.
151 `OPT_INTEGER(short, long, &int_var, description)`::
152 Introduce an option with integer argument.
153 The integer is put into `int_var`.
155 `OPT_DATE(short, long, &int_var, description)`::
156 Introduce an option with date argument, see `approxidate()`.
157 The timestamp is put into `int_var`.
159 `OPT_CALLBACK(short, long, &var, arg_str, description, func_ptr)`::
160 Introduce an option with argument.
161 The argument will be fed into the function given by `func_ptr`
162 and the result will be put into `var`.
163 See 'Option Callbacks' below for a more elaborate description.
165 `OPT_ARGUMENT(long, description)`::
166 Introduce a long-option argument that will be kept in `argv[]`.
169 The last element of the array must be `OPT_END()`.
171 If not stated otherwise, interpret the arguments as follows:
173 * `short` is a character for the short option
174 (e.g. `\'e\'` for `-e`, use `0` to omit),
176 * `long` is a string for the long option
177 (e.g. `"example"` for `\--example`, use `NULL` to omit),
179 * `int_var` is an integer variable,
181 * `str_var` is a string variable (`char *`),
183 * `arg_str` is the string that is shown as argument
184 (e.g. `"branch"` will result in `<branch>`).
185 If set to `NULL`, three dots (`...`) will be displayed.
187 * `description` is a short string to describe the effect of the option.
188 It shall begin with a lower-case letter and a full stop (`.`) shall be
194 The function must be defined in this form:
196 int func(const struct option *opt, const char *arg, int unset)
198 The callback mechanism is as follows:
200 * Inside `funct`, the only interesting member of the structure
201 given by `opt` is the void pointer `opt->value`.
202 `\*opt->value` will be the value that is saved into `var`, if you
203 use `OPT_CALLBACK()`.
204 For example, do `*(unsigned long *)opt->value = 42;` to get 42
205 into an `unsigned long` variable.
207 * Return value `0` indicates success and non-zero return
208 value will invoke `usage_with_options()` and, thus, die.
210 * If the user negates the option, `arg` is `NULL` and `unset` is 1.
212 Sophisticated option parsing
213 ----------------------------
215 If you need, for example, option callbacks with optional arguments
216 or without arguments at all, or if you need other special cases,
217 that are not handled by the macros above, you need to specify the
218 members of the `option` structure manually.
220 This is not covered in this document, but well documented
221 in `parse-options.h` itself.
226 See `test-parse-options.c` and
233 for real-world examples.