diff options
Diffstat (limited to 'Documentation/technical/api-parse-options.txt')
| -rw-r--r-- | Documentation/technical/api-parse-options.txt | 49 |
1 files changed, 45 insertions, 4 deletions
diff --git a/Documentation/technical/api-parse-options.txt b/Documentation/technical/api-parse-options.txt index acfd5dc..61fa6ee 100644 --- a/Documentation/technical/api-parse-options.txt +++ b/Documentation/technical/api-parse-options.txt @@ -8,7 +8,8 @@ Basics ------ The argument vector `argv[]` may usually contain mandatory or optional -'non-option arguments', e.g. a filename or a branch, and 'options'. +'non-option arguments', e.g. a filename or a branch, 'options', and +'subcommands'. Options are optional arguments that start with a dash and that allow to change the behavior of a command. @@ -48,6 +49,33 @@ The parse-options API allows: option, e.g. `-a -b --option -- --this-is-a-file` indicates that `--this-is-a-file` must not be processed as an option. +Subcommands are special in a couple of ways: + +* Subcommands only have long form, and they have no double dash prefix, no + negated form, and no description, and they don't take any arguments, and + can't be abbreviated. + +* There must be exactly one subcommand among the arguments, or zero if the + command has a default operation mode. + +* All arguments following the subcommand are considered to be arguments of + the subcommand, and, conversely, arguments meant for the subcommand may + not precede the subcommand. + +Therefore, if the options array contains at least one subcommand and +`parse_options()` encounters the first dashless argument, it will either: + +* stop and return, if that dashless argument is a known subcommand, setting + `value` to the function pointer associated with that subcommand, storing + the name of the subcommand in argv[0], and leaving the rest of the + arguments unprocessed, or + +* stop and return, if it was invoked with the `PARSE_OPT_SUBCOMMAND_OPTIONAL` + flag and that dashless argument doesn't match any subcommands, leaving + `value` unchanged and the rest of the arguments unprocessed, or + +* show error and usage, and abort. + Steps to parse options ---------------------- @@ -90,8 +118,8 @@ Flags are the bitwise-or of: 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 +`PARSE_OPT_KEEP_UNKNOWN_OPT`:: + Keep unknown options 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 @@ -101,6 +129,8 @@ Flags are the bitwise-or of: 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. + Note that non-option arguments are always kept, even without + this flag. `PARSE_OPT_NO_INTERNAL_HELP`:: By default, parse_options() handles `-h`, `--help` and @@ -108,6 +138,13 @@ Flags are the bitwise-or of: turns it off and allows one to add custom handlers for these options, or to just leave them unknown. +`PARSE_OPT_SUBCOMMAND_OPTIONAL`:: + Don't error out when no subcommand is specified. + +Note that `PARSE_OPT_STOP_AT_NON_OPTION` is incompatible with subcommands; +while `PARSE_OPT_KEEP_DASHDASH` and `PARSE_OPT_KEEP_UNKNOWN_OPT` can only be +used with subcommands when combined with `PARSE_OPT_SUBCOMMAND_OPTIONAL`. + Data Structure -------------- @@ -236,10 +273,14 @@ There are some macros to easily define options: `OPT_CMDMODE(short, long, &int_var, description, enum_val)`:: Define an "operation mode" option, only one of which in the same group of "operating mode" options that share the same `int_var` - can be given by the user. `enum_val` is set to `int_var` when the + can be given by the user. `int_var` is set to `enum_val` when the option is used, but an error is reported if other "operating mode" option has already set its value to the same `int_var`. + In new commands consider using subcommands instead. +`OPT_SUBCOMMAND(long, &fn_ptr, subcommand_fn)`:: + Define a subcommand. `subcommand_fn` is put into `fn_ptr` when + this subcommand is used. The last element of the array must be `OPT_END()`. |