1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
|
parse-options API
=================
The parse-options API is used to parse and massage options in git
and to provide a usage help with consistent look.
Basics
------
The argument vector `argv[]` may usually contain mandatory or optional
'non-option arguments', e.g. a filename or a branch, and 'options'.
Options are optional arguments that start with a dash and
that allow to change the behavior of a command.
* There are basically three types of options:
'boolean' options,
options with (mandatory) 'arguments' and
options with 'optional arguments'
(i.e. a boolean option that can be adjusted).
* There are basically two forms of options:
'Short options' consist of one dash (`-`) and one alphanumeric
character.
'Long options' begin with two dashes (`\--`) and some
alphanumeric characters.
* Options are case-sensitive.
Please define 'lower-case long options' only.
The parse-options API allows:
* 'sticked' and 'separate form' of options with arguments.
`-oArg` is sticked, `-o Arg` is separate form.
`\--option=Arg` is sticked, `\--option Arg` is separate form.
* Long options may be 'abbreviated', as long as the abbreviation
is unambiguous.
* Short options may be bundled, e.g. `-a -b` can be specified as `-ab`.
* Boolean long options can be 'negated' (or 'unset') by prepending
`no-`, e.g. `\--no-abbrev` instead of `\--abbrev`. Conversely,
options that begin with `no-` can be 'negated' by removing it.
* Options and non-option arguments can clearly be separated using the `\--`
option, e.g. `-a -b \--option \-- \--this-is-a-file` indicates that
`\--this-is-a-file` must not be processed as an option.
Steps to parse options
----------------------
. `#include "parse-options.h"`
. define a NULL-terminated
`static const char * const builtin_foo_usage[]` array
containing alternative usage strings
. define `builtin_foo_options` array as described below
in section 'Data Structure'.
. in `cmd_foo(int argc, const char **argv, const char *prefix)`
call
argc = parse_options(argc, argv, prefix, builtin_foo_options, builtin_foo_usage, flags);
+
`parse_options()` will filter out the processed options of `argv[]` and leave the
non-option arguments in `argv[]`.
`argc` is updated appropriately because of the assignment.
+
You can also pass NULL instead of a usage array as the fifth parameter of
parse_options(), to avoid displaying a help screen with usage info and
option list. This should only be done if necessary, e.g. to implement
a limited parser for only a subset of the options that needs to be run
before the full parser, which in turn shows the full help message.
+
Flags are the bitwise-or of:
`PARSE_OPT_KEEP_DASHDASH`::
Keep the `\--` that usually separates options from
non-option arguments.
`PARSE_OPT_STOP_AT_NON_OPTION`::
Usually the whole argument vector is massaged and reordered.
Using this flag, processing is stopped at the first non-option
argument.
`PARSE_OPT_KEEP_ARGV0`::
Keep the first argument, which contains the program name. It's
removed from argv[] by default.
`PARSE_OPT_KEEP_UNKNOWN`::
Keep unknown arguments instead of erroring out. This doesn't
work for all combinations of arguments as users might expect
it to do. E.g. if the first argument in `--unknown --known`
takes a value (which we can't know), the second one is
mistakenly interpreted as a known option. Similarly, if
`PARSE_OPT_STOP_AT_NON_OPTION` is set, the second argument in
`--unknown value` will be mistakenly interpreted as a
non-option, not as a value belonging to the unknown option,
the parser early. That's why parse_options() errors out if
both options are set.
`PARSE_OPT_NO_INTERNAL_HELP`::
By default, parse_options() handles `-h`, `--help` and
`--help-all` internally, by showing a help screen. This option
turns it off and allows one to add custom handlers for these
options, or to just leave them unknown.
Data Structure
--------------
The main data structure is an array of the `option` struct,
say `static struct option builtin_add_options[]`.
There are some macros to easily define options:
`OPT__ABBREV(&int_var)`::
Add `\--abbrev[=<n>]`.
`OPT__COLOR(&int_var, description)`::
Add `\--color[=<when>]` and `--no-color`.
`OPT__DRY_RUN(&int_var, description)`::
Add `-n, \--dry-run`.
`OPT__FORCE(&int_var, description)`::
Add `-f, \--force`.
`OPT__QUIET(&int_var, description)`::
Add `-q, \--quiet`.
`OPT__VERBOSE(&int_var, description)`::
Add `-v, \--verbose`.
`OPT_GROUP(description)`::
Start an option group. `description` is a short string that
describes the group or an empty string.
Start the description with an upper-case letter.
`OPT_BOOL(short, long, &int_var, description)`::
Introduce a boolean option. `int_var` is set to one with
`--option` and set to zero with `--no-option`.
`OPT_COUNTUP(short, long, &int_var, description)`::
Introduce a count-up option.
`int_var` is incremented on each use of `--option`, and
reset to zero with `--no-option`.
`OPT_BIT(short, long, &int_var, description, mask)`::
Introduce a boolean option.
If used, `int_var` is bitwise-ored with `mask`.
`OPT_NEGBIT(short, long, &int_var, description, mask)`::
Introduce a boolean option.
If used, `int_var` is bitwise-anded with the inverted `mask`.
`OPT_SET_INT(short, long, &int_var, description, integer)`::
Introduce an integer option.
`int_var` is set to `integer` with `--option`, and
reset to zero with `--no-option`.
`OPT_SET_PTR(short, long, &ptr_var, description, ptr)`::
Introduce a boolean option.
If used, set `ptr_var` to `ptr`.
`OPT_STRING(short, long, &str_var, arg_str, description)`::
Introduce an option with string argument.
The string argument is put into `str_var`.
`OPT_INTEGER(short, long, &int_var, description)`::
Introduce an option with integer argument.
The integer is put into `int_var`.
`OPT_DATE(short, long, &int_var, description)`::
Introduce an option with date argument, see `approxidate()`.
The timestamp is put into `int_var`.
`OPT_CALLBACK(short, long, &var, arg_str, description, func_ptr)`::
Introduce an option with argument.
The argument will be fed into the function given by `func_ptr`
and the result will be put into `var`.
See 'Option Callbacks' below for a more elaborate description.
`OPT_FILENAME(short, long, &var, description)`::
Introduce an option with a filename argument.
The filename will be prefixed by passing the filename along with
the prefix argument of `parse_options()` to `prefix_filename()`.
`OPT_ARGUMENT(long, description)`::
Introduce a long-option argument that will be kept in `argv[]`.
`OPT_NUMBER_CALLBACK(&var, description, func_ptr)`::
Recognize numerical options like -123 and feed the integer as
if it was an argument to the function given by `func_ptr`.
The result will be put into `var`. There can be only one such
option definition. It cannot be negated and it takes no
arguments. Short options that happen to be digits take
precedence over it.
`OPT_COLOR_FLAG(short, long, &int_var, description)`::
Introduce an option that takes an optional argument that can
have one of three values: "always", "never", or "auto". If the
argument is not given, it defaults to "always". The `--no-` form
works like `--long=never`; it cannot take an argument. If
"always", set `int_var` to 1; if "never", set `int_var` to 0; if
"auto", set `int_var` to 1 if stdout is a tty or a pager,
0 otherwise.
`OPT_NOOP_NOARG(short, long)`::
Introduce an option that has no effect and takes no arguments.
Use it to hide deprecated options that are still to be recognized
and ignored silently.
The last element of the array must be `OPT_END()`.
If not stated otherwise, interpret the arguments as follows:
* `short` is a character for the short option
(e.g. `{apostrophe}e{apostrophe}` for `-e`, use `0` to omit),
* `long` is a string for the long option
(e.g. `"example"` for `\--example`, use `NULL` to omit),
* `int_var` is an integer variable,
* `str_var` is a string variable (`char *`),
* `arg_str` is the string that is shown as argument
(e.g. `"branch"` will result in `<branch>`).
If set to `NULL`, three dots (`...`) will be displayed.
* `description` is a short string to describe the effect of the option.
It shall begin with a lower-case letter and a full stop (`.`) shall be
omitted at the end.
Option Callbacks
----------------
The function must be defined in this form:
int func(const struct option *opt, const char *arg, int unset)
The callback mechanism is as follows:
* Inside `func`, the only interesting member of the structure
given by `opt` is the void pointer `opt\->value`.
`\*opt\->value` will be the value that is saved into `var`, if you
use `OPT_CALLBACK()`.
For example, do `*(unsigned long *)opt\->value = 42;` to get 42
into an `unsigned long` variable.
* Return value `0` indicates success and non-zero return
value will invoke `usage_with_options()` and, thus, die.
* If the user negates the option, `arg` is `NULL` and `unset` is 1.
Sophisticated option parsing
----------------------------
If you need, for example, option callbacks with optional arguments
or without arguments at all, or if you need other special cases,
that are not handled by the macros above, you need to specify the
members of the `option` structure manually.
This is not covered in this document, but well documented
in `parse-options.h` itself.
Examples
--------
See `test-parse-options.c` and
`builtin-add.c`,
`builtin-clone.c`,
`builtin-commit.c`,
`builtin-fetch.c`,
`builtin-fsck.c`,
`builtin-rm.c`
for real-world examples.
|
