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| <body class="article"> | |
| <div id="header"> | |
| <h1>parse-options API</h1> | |
| </div> | |
| <div id="content"> | |
| <div id="preamble"> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>The parse-options API is used to parse and massage options in Git | |
| and to provide a usage help with consistent look.</p></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_basics">Basics</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>The argument vector <code>argv[]</code> may usually contain mandatory or optional | |
| <em>non-option arguments</em>, e.g. a filename or a branch, <em>options</em>, and | |
| <em>subcommands</em>. | |
| Options are optional arguments that start with a dash and | |
| that allow to change the behavior of a command.</p></div> | |
| <div class="ulist"><ul> | |
| <li> | |
| <p> | |
| There are basically three types of options: | |
| <em>boolean</em> options, | |
| options with (mandatory) <em>arguments</em> and | |
| options with <em>optional arguments</em> | |
| (i.e. a boolean option that can be adjusted). | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| There are basically two forms of options: | |
| <em>Short options</em> consist of one dash (<code>-</code>) and one alphanumeric | |
| character. | |
| <em>Long options</em> begin with two dashes (<code>--</code>) and some | |
| alphanumeric characters. | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| Options are case-sensitive. | |
| Please define <em>lower-case long options</em> only. | |
| </p> | |
| </li> | |
| </ul></div> | |
| <div class="paragraph"><p>The parse-options API allows:</p></div> | |
| <div class="ulist"><ul> | |
| <li> | |
| <p> | |
| <em>stuck</em> and <em>separate form</em> of options with arguments. | |
| <code>-oArg</code> is stuck, <code>-o Arg</code> is separate form. | |
| <code>--option=Arg</code> is stuck, <code>--option Arg</code> is separate form. | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| Long options may be <em>abbreviated</em>, as long as the abbreviation | |
| is unambiguous. | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| Short options may be bundled, e.g. <code>-a -b</code> can be specified as <code>-ab</code>. | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| Boolean long options can be <em>negated</em> (or <em>unset</em>) by prepending | |
| <code>no-</code>, e.g. <code>--no-abbrev</code> instead of <code>--abbrev</code>. Conversely, | |
| options that begin with <code>no-</code> can be <em>negated</em> by removing it. | |
| Other long options can be unset (e.g., set string to NULL, set | |
| integer to 0) by prepending <code>no-</code>. | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| Options and non-option arguments can clearly be separated using the <code>--</code> | |
| option, e.g. <code>-a -b --option -- --this-is-a-file</code> indicates that | |
| <code>--this-is-a-file</code> must not be processed as an option. | |
| </p> | |
| </li> | |
| </ul></div> | |
| <div class="paragraph"><p>Subcommands are special in a couple of ways:</p></div> | |
| <div class="ulist"><ul> | |
| <li> | |
| <p> | |
| 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. | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| There must be exactly one subcommand among the arguments, or zero if the | |
| command has a default operation mode. | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| 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. | |
| </p> | |
| </li> | |
| </ul></div> | |
| <div class="paragraph"><p>Therefore, if the options array contains at least one subcommand and | |
| <code>parse_options()</code> encounters the first dashless argument, it will either:</p></div> | |
| <div class="ulist"><ul> | |
| <li> | |
| <p> | |
| stop and return, if that dashless argument is a known subcommand, setting | |
| <code>value</code> 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 | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| stop and return, if it was invoked with the <code>PARSE_OPT_SUBCOMMAND_OPTIONAL</code> | |
| flag and that dashless argument doesn’t match any subcommands, leaving | |
| <code>value</code> unchanged and the rest of the arguments unprocessed, or | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| show error and usage, and abort. | |
| </p> | |
| </li> | |
| </ul></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_steps_to_parse_options">Steps to parse options</h2> | |
| <div class="sectionbody"> | |
| <div class="olist arabic"><ol class="arabic"> | |
| <li> | |
| <p> | |
| <code>#include "parse-options.h"</code> | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| define a NULL-terminated | |
| <code>static const char * const builtin_foo_usage[]</code> array | |
| containing alternative usage strings | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| define <code>builtin_foo_options</code> array as described below | |
| in section <em>Data Structure</em>. | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| in <code>cmd_foo(int argc, const char **argv, const char *prefix)</code> | |
| call | |
| </p> | |
| <div class="literalblock"> | |
| <div class="content"> | |
| <pre><code>argc = parse_options(argc, argv, prefix, builtin_foo_options, builtin_foo_usage, flags);</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p><code>parse_options()</code> will filter out the processed options of <code>argv[]</code> and leave the | |
| non-option arguments in <code>argv[]</code>. | |
| <code>argc</code> is updated appropriately because of the assignment.</p></div> | |
| <div class="paragraph"><p>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.</p></div> | |
| <div class="paragraph"><p>Flags are the bitwise-or of:</p></div> | |
| <div class="dlist"><dl> | |
| <dt class="hdlist1"> | |
| <code>PARSE_OPT_KEEP_DASHDASH</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Keep the <code>--</code> that usually separates options from | |
| non-option arguments. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>PARSE_OPT_STOP_AT_NON_OPTION</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Usually the whole argument vector is massaged and reordered. | |
| Using this flag, processing is stopped at the first non-option | |
| argument. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>PARSE_OPT_KEEP_ARGV0</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Keep the first argument, which contains the program name. It’s | |
| removed from argv[] by default. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>PARSE_OPT_KEEP_UNKNOWN_OPT</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| 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 <code>--unknown --known</code> | |
| takes a value (which we can’t know), the second one is | |
| mistakenly interpreted as a known option. Similarly, if | |
| <code>PARSE_OPT_STOP_AT_NON_OPTION</code> is set, the second argument in | |
| <code>--unknown value</code> 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. | |
| Note that non-option arguments are always kept, even without | |
| this flag. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>PARSE_OPT_NO_INTERNAL_HELP</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| By default, parse_options() handles <code>-h</code>, <code>--help</code> and | |
| <code>--help-all</code> 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. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>PARSE_OPT_SUBCOMMAND_OPTIONAL</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Don’t error out when no subcommand is specified. | |
| </p> | |
| </dd> | |
| </dl></div> | |
| </li> | |
| </ol></div> | |
| <div class="paragraph"><p>Note that <code>PARSE_OPT_STOP_AT_NON_OPTION</code> is incompatible with subcommands; | |
| while <code>PARSE_OPT_KEEP_DASHDASH</code> and <code>PARSE_OPT_KEEP_UNKNOWN_OPT</code> can only be | |
| used with subcommands when combined with <code>PARSE_OPT_SUBCOMMAND_OPTIONAL</code>.</p></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_data_structure">Data Structure</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>The main data structure is an array of the <code>option</code> struct, | |
| say <code>static struct option builtin_add_options[]</code>. | |
| There are some macros to easily define options:</p></div> | |
| <div class="dlist"><dl> | |
| <dt class="hdlist1"> | |
| <code>OPT__ABBREV(&int_var)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Add <code>--abbrev[=<n>]</code>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT__COLOR(&int_var, description)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Add <code>--color[=<when>]</code> and <code>--no-color</code>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT__DRY_RUN(&int_var, description)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Add <code>-n, --dry-run</code>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT__FORCE(&int_var, description)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Add <code>-f, --force</code>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT__QUIET(&int_var, description)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Add <code>-q, --quiet</code>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT__VERBOSE(&int_var, description)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Add <code>-v, --verbose</code>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_GROUP(description)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Start an option group. <code>description</code> is a short string that | |
| describes the group or an empty string. | |
| Start the description with an upper-case letter. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_BOOL(short, long, &int_var, description)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Introduce a boolean option. <code>int_var</code> is set to one with | |
| <code>--option</code> and set to zero with <code>--no-option</code>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_COUNTUP(short, long, &int_var, description)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Introduce a count-up option. | |
| Each use of <code>--option</code> increments <code>int_var</code>, starting from zero | |
| (even if initially negative), and <code>--no-option</code> resets it to | |
| zero. To determine if <code>--option</code> or <code>--no-option</code> was encountered at | |
| all, initialize <code>int_var</code> to a negative value, and if it is still | |
| negative after parse_options(), then neither <code>--option</code> nor | |
| <code>--no-option</code> was seen. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_BIT(short, long, &int_var, description, mask)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Introduce a boolean option. | |
| If used, <code>int_var</code> is bitwise-ored with <code>mask</code>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_NEGBIT(short, long, &int_var, description, mask)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Introduce a boolean option. | |
| If used, <code>int_var</code> is bitwise-anded with the inverted <code>mask</code>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_SET_INT(short, long, &int_var, description, integer)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Introduce an integer option. | |
| <code>int_var</code> is set to <code>integer</code> with <code>--option</code>, and | |
| reset to zero with <code>--no-option</code>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_STRING(short, long, &str_var, arg_str, description)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Introduce an option with string argument. | |
| The string argument is put into <code>str_var</code>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_STRING_LIST(short, long, &struct string_list, arg_str, description)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Introduce an option with string argument. | |
| The string argument is stored as an element in <code>string_list</code>. | |
| Use of <code>--no-option</code> will clear the list of preceding values. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_INTEGER(short, long, &int_var, description)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Introduce an option with integer argument. | |
| The integer is put into <code>int_var</code>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_MAGNITUDE(short, long, &unsigned_long_var, description)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Introduce an option with a size argument. The argument must be a | |
| non-negative integer and may include a suffix of <em>k</em>, <em>m</em> or <em>g</em> to | |
| scale the provided value by 1024, 1024<sup>2 or 1024</sup>3 respectively. | |
| The scaled value is put into <code>unsigned_long_var</code>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_EXPIRY_DATE(short, long, &timestamp_t_var, description)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Introduce an option with expiry date argument, see <code>parse_expiry_date()</code>. | |
| The timestamp is put into <code>timestamp_t_var</code>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_CALLBACK(short, long, &var, arg_str, description, func_ptr)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Introduce an option with argument. | |
| The argument will be fed into the function given by <code>func_ptr</code> | |
| and the result will be put into <code>var</code>. | |
| See <em>Option Callbacks</em> below for a more elaborate description. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_FILENAME(short, long, &var, description)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Introduce an option with a filename argument. | |
| The filename will be prefixed by passing the filename along with | |
| the prefix argument of <code>parse_options()</code> to <code>prefix_filename()</code>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_NUMBER_CALLBACK(&var, description, func_ptr)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Recognize numerical options like -123 and feed the integer as | |
| if it was an argument to the function given by <code>func_ptr</code>. | |
| The result will be put into <code>var</code>. 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. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_COLOR_FLAG(short, long, &int_var, description)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| 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 <code>--no-</code> form | |
| works like <code>--long=never</code>; it cannot take an argument. If | |
| "always", set <code>int_var</code> to 1; if "never", set <code>int_var</code> to 0; if | |
| "auto", set <code>int_var</code> to 1 if stdout is a tty or a pager, | |
| 0 otherwise. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_NOOP_NOARG(short, long)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| 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. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_PASSTHRU(short, long, &char_var, arg_str, description, flags)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Introduce an option that will be reconstructed into a char* string, | |
| which must be initialized to NULL. This is useful when you need to | |
| pass the command-line option to another command. Any previous value | |
| will be overwritten, so this should only be used for options where | |
| the last one specified on the command line wins. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_PASSTHRU_ARGV(short, long, &strvec_var, arg_str, description, flags)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Introduce an option where all instances of it on the command-line will | |
| be reconstructed into a strvec. This is useful when you need to | |
| pass the command-line option, which can be specified multiple times, | |
| to another command. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_CMDMODE(short, long, &int_var, description, enum_val)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Define an "operation mode" option, only one of which in the same | |
| group of "operating mode" options that share the same <code>int_var</code> | |
| can be given by the user. <code>int_var</code> is set to <code>enum_val</code> when the | |
| option is used, but an error is reported if other "operating mode" | |
| option has already set its value to the same <code>int_var</code>. | |
| In new commands consider using subcommands instead. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| <code>OPT_SUBCOMMAND(long, &fn_ptr, subcommand_fn)</code> | |
| </dt> | |
| <dd> | |
| <p> | |
| Define a subcommand. <code>subcommand_fn</code> is put into <code>fn_ptr</code> when | |
| this subcommand is used. | |
| </p> | |
| </dd> | |
| </dl></div> | |
| <div class="paragraph"><p>The last element of the array must be <code>OPT_END()</code>.</p></div> | |
| <div class="paragraph"><p>If not stated otherwise, interpret the arguments as follows:</p></div> | |
| <div class="ulist"><ul> | |
| <li> | |
| <p> | |
| <code>short</code> is a character for the short option | |
| (e.g. <code>'e'</code> for <code>-e</code>, use <code>0</code> to omit), | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| <code>long</code> is a string for the long option | |
| (e.g. <code>"example"</code> for <code>--example</code>, use <code>NULL</code> to omit), | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| <code>int_var</code> is an integer variable, | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| <code>str_var</code> is a string variable (<code>char *</code>), | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| <code>arg_str</code> is the string that is shown as argument | |
| (e.g. <code>"branch"</code> will result in <code><branch></code>). | |
| If set to <code>NULL</code>, three dots (<code>...</code>) will be displayed. | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| <code>description</code> is a short string to describe the effect of the option. | |
| It shall begin with a lower-case letter and a full stop (<code>.</code>) shall be | |
| omitted at the end. | |
| </p> | |
| </li> | |
| </ul></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_option_callbacks">Option Callbacks</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>The function must be defined in this form:</p></div> | |
| <div class="literalblock"> | |
| <div class="content"> | |
| <pre><code>int func(const struct option *opt, const char *arg, int unset)</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>The callback mechanism is as follows:</p></div> | |
| <div class="ulist"><ul> | |
| <li> | |
| <p> | |
| Inside <code>func</code>, the only interesting member of the structure | |
| given by <code>opt</code> is the void pointer <code>opt->value</code>. | |
| <code>*opt->value</code> will be the value that is saved into <code>var</code>, if you | |
| use <code>OPT_CALLBACK()</code>. | |
| For example, do <code>*(unsigned long *)opt->value = 42;</code> to get 42 | |
| into an <code>unsigned long</code> variable. | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| Return value <code>0</code> indicates success and non-zero return | |
| value will invoke <code>usage_with_options()</code> and, thus, die. | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| If the user negates the option, <code>arg</code> is <code>NULL</code> and <code>unset</code> is 1. | |
| </p> | |
| </li> | |
| </ul></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_sophisticated_option_parsing">Sophisticated option parsing</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>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 <code>option</code> structure manually.</p></div> | |
| <div class="paragraph"><p>This is not covered in this document, but well documented | |
| in <code>parse-options.h</code> itself.</p></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_examples">Examples</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>See <code>test-parse-options.c</code> and | |
| <code>builtin/add.c</code>, | |
| <code>builtin/clone.c</code>, | |
| <code>builtin/commit.c</code>, | |
| <code>builtin/fetch.c</code>, | |
| <code>builtin/fsck.c</code>, | |
| <code>builtin/rm.c</code> | |
| for real-world examples.</p></div> | |
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| Last updated | |
| 2023-04-17 17:57:53 PDT | |
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