| @node Recognizing Option Arguments |
| @section Recognizing Option Arguments |
| |
| The module @samp{argmatch} provides a simple textual user interface to a |
| finite choice. It is for example well suited to recognize arguments of |
| options or values of environment variables that accept a fixed set of valid |
| choices. |
| |
| These choices may be denoted by synonyms, such as `none' and `off' below. |
| |
| @smallexample |
| $ @kbd{my_cp --backup=none foo bar} |
| $ @kbd{my_cp --backup=non foo bar} |
| $ @kbd{my_cp --backup=no foo bar} |
| $ @kbd{my_cp --backup=n foo bar} |
| my_cp: ambiguous argument 'n' for 'backup type' |
| Valid arguments are: |
| - 'no', 'none', 'off' |
| - 'numbered', 't', 'newstyle' |
| - 'existing', 'nil', 'numbered-existing' |
| - 'simple', 'never', 'single' |
| Try 'my_cp --help' for more information. |
| $ @kbd{my_cp --backup=num foo bar} |
| $ @kbd{my_cp --backup=true foo bar} |
| my_cp: invalid argument 'true' for 'backup type' |
| Valid arguments are: |
| - 'no', 'none', 'off' |
| - 'numbered', 't', 'newstyle' |
| - 'existing', 'nil', 'numbered-existing' |
| - 'simple', 'never', 'single' |
| Try 'my_cp --help' for more information. |
| @end smallexample |
| |
| To set up @code{argmatch}, first call @samp{ARGMATCH_DEFINE_GROUP |
| (@var{name}, @var{type})} with the name of the argmatch group name, and the |
| value type. For instance: |
| |
| @smallexample |
| enum backup_type |
| @{ |
| no_backups, |
| simple_backups, |
| numbered_existing_backups, |
| numbered_backups |
| @}; |
| |
| ARGMATCH_DEFINE_GROUP (backup, enum backup_type); |
| @end smallexample |
| |
| @noindent |
| This defines a few types and functions named @code{argmatch_@var{name}_*}. |
| Introduce the array that defines the mapping from user-input to actual |
| value, with a terminator: |
| |
| @example |
| static const argmatch_backup_arg argmatch_backup_args[] = |
| @{ |
| @{ "no", no_backups @}, |
| @{ "none", no_backups @}, |
| @{ "off", no_backups @}, |
| @{ "simple", simple_backups @}, |
| @{ "never", simple_backups @}, |
| @{ "single", simple_backups @}, |
| @{ "existing", numbered_existing_backups @}, |
| @{ "nil", numbered_existing_backups @}, |
| @{ "numbered-existing", numbered_existing_backups @}, |
| @{ "numbered", numbered_backups @}, |
| @{ "t", numbered_backups @}, |
| @{ "newstyle", numbered_backups @}, |
| @{ NULL, no_backups @} |
| @}; |
| @end example |
| |
| @noindent |
| Then introduce the array that defines the values, also with a terminator. |
| Document only once per group of synonyms: |
| |
| @example |
| static const argmatch_backup_doc argmatch_backup_docs[] = |
| @{ |
| @{ "no", N_("never make backups (even if --backup is given)") @}, |
| @{ "numbered", N_("make numbered backups") @}, |
| @{ "existing", N_("numbered if numbered backups exist, simple otherwise") @}, |
| @{ "simple", N_("always make simple backups") @}, |
| @{ NULL, NULL @} |
| @}; |
| @end example |
| |
| @noindent |
| Finally, define the argmatch group: |
| |
| @example |
| const argmatch_backup_group_type argmatch_backup_group = |
| @{ |
| argmatch_backup_args, |
| argmatch_backup_docs, |
| N_("\ |
| The backup suffix is '~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX.\n\ |
| The version control method may be selected via the --backup option or through\n\ |
| the VERSION_CONTROL environment variable. Here are the values:\n"), |
| NULL |
| @}; |
| @end example |
| |
| @sp 1 |
| |
| To use the argmatch group: |
| |
| @smallexample |
| ptrdiff_t i = argmatch_backup_choice ("--backup", "none"); |
| // argmatch_backup_group.args[i].arg is "none", so its value |
| // is argmatch_backup_group.args[i].val. |
| // Return -1 on invalid argument, and -2 on ambiguity. |
| |
| enum backup_type val = *argmatch_backup_value ("--backup", "none"); |
| // Returns a pointer to the value, and exit on errors. |
| // So argmatch_backup_group.args[i].val == val. |
| |
| const char *arg = argmatch_backup_argument (&no_backups); |
| // arg is "no". |
| |
| // Print the documentation on stdout. |
| argmatch_backup_usage (stdout); |
| // Gives: |
| // |
| // The backup suffix is '~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX. |
| // The version control method may be selected via the --backup option or through |
| // the VERSION_CONTROL environment variable. Here are the values: |
| // |
| // no, none, off never make backups (even if --backup is given) |
| // numbered, t, newstyle |
| // make numbered backups |
| // existing, nil, numbered-existing |
| // numbered if numbered backups exist, simple otherwise |
| // simple, never, single |
| // always make simple backups |
| @end smallexample |