
GETARG(3)                  UNIX Programmer's Manual                  GETARG(3)

NNAAMMEE
     ggeettaarrgg, aarrgg__pprriinnttuussaaggee - collect command line options

SSYYNNOOPPSSIISS
     _i_n_t
     ggeettaarrgg(_s_t_r_u_c_t _g_e_t_a_r_g_s _*_a_r_g_s, _s_i_z_e___t _n_u_m___a_r_g_s, _i_n_t _a_r_g_c, _c_h_a_r _*_*_a_r_g_v,
             _i_n_t _*_o_p_t_i_n_d)

     _v_o_i_d
     aarrgg__pprriinnttuussaaggee(_s_t_r_u_c_t _g_e_t_a_r_g_s _*_a_r_g_s, _s_i_z_e___t _n_u_m___a_r_g_s,
             _c_o_n_s_t _c_h_a_r _*_p_r_o_g_n_a_m_e, _c_o_n_s_t _c_h_a_r _*_e_x_t_r_a___s_t_r_i_n_g)

DDEESSCCRRIIPPTTIIOONN
     ggeettaarrgg() collects any command line options given to a program in an easi-
     ly used way.  aarrgg__pprriinnttuussaaggee() pretty-prints the available options, with
     a short help text.

     _a_r_g_s is the option specification to use, and it's an array of _s_t_r_u_c_t
     _g_e_t_a_r_g_s elements.  _n_u_m___a_r_g_s is the size of _a_r_g_s (in elements).  _a_r_g_c and
     _a_r_g_v are the argument count and argument vector to extract option from.
     _o_p_t_i_n_d is a pointer to an integer where the index to the last processed
     argument is stored, it must be initialised to the first index (minus one)
     to process (normally 0) before the first call.

     _a_r_g___p_r_i_n_t_u_s_a_g_e take the same _a_r_g_s and _n_u_m___a_r_g_s as getarg; _p_r_o_g_n_a_m_e is the
     name of the program (to be used in the help text), and _e_x_t_r_a___s_t_r_i_n_g is a
     string to print after the actual options to indicate more arguments. The
     usefulness of this function is realised only be people who has used pro-
     grams that has help strings that doesn't match what the code does.

     The _g_e_t_a_r_g_s struct has the following elements.

     struct getargs{
         const char *long_name;
         char short_name;
         enum { arg_integer,
                arg_string,
                arg_flag,
                arg_negative_flag,
                arg_strings,
                arg_double,
                arg_collect
         } type;
         void *value;
         const char *help;
         const char *arg_help;
     };

     _l_o_n_g___n_a_m_e is the long name of the option, it can be NULL, if you don't
     want a long name.  _s_h_o_r_t___n_a_m_e is the characted to use as short option, it
     can be zero. If the option has a value the _v_a_l_u_e field gets filled in
     with that value interpreted as specified by the _t_y_p_e field.  _h_e_l_p is a
     longer help string for the option as a whole, if it's NULL the help text
     for the option is omitted (but it's still displayed in the synopsis).
     _a_r_g___h_e_l_p is a description of the argument, if NULL a default value will
     be used, depending on the type of the option:

     arg_integer        the argument is a signed integer, and _v_a_l_u_e should
                        point to an _i_n_t.

     _a_r_g___s_t_r_i_n_g         the argument is a string, and _v_a_l_u_e should point to a

                        _c_h_a_r_*.

     _a_r_g___f_l_a_g           the argument is a flag, and _v_a_l_u_e should point to a
                        _i_n_t. It gets filled in with either zero or one, de-
                        pending on how the option is given, the normal case
                        being one. Note that if the option isn't given, the
                        value isn't altered, so it should be initialised to
                        some useful default.

     _a_r_g___n_e_g_a_t_i_v_e___f_l_a_g this is the same as _a_r_g___f_l_a_g but it reverses the mean-
                        ing of the flag (a given short option clears the
                        flag), and the synopsis of a long option is negated.

     _a_r_g___s_t_r_i_n_g_s        the argument can be given multiple times, and the val-
                        ues are collected in an array; _v_a_l_u_e should be a
                        pointer to a _s_t_r_u_c_t _g_e_t_a_r_g___s_t_r_i_n_g_s structure, which
                        holds a length and a string pointer.

     _a_r_g___d_o_u_b_l_e         argument is a double precision floating point value,
                        and _v_a_l_u_e should point to a _d_o_u_b_l_e.

     _a_r_g___c_o_l_l_e_c_t        allows more fine-grained control of the option parsing
                        process.  _v_a_l_u_e should be a pointer to a
                        _g_e_t_a_r_g___c_o_l_l_e_c_t___i_n_f_o structure:

                        typedef int (*getarg_collect_func)(int short_opt,
                                                           int argc,
                                                           char **argv,
                                                           int *optind,
                                                           int *optarg,
                                                           void *data);

                        typedef struct getarg_collect_info {
                            getarg_collect_func func;
                            void *data;
                        } getarg_collect_info;

                        With the _f_u_n_c member set to a function to call, and
                        _d_a_t_a to some application specific data. The parameters
                        to the collect function are:

                        _s_h_o_r_t___f_l_a_g non-zero if this call is via a short option
                        flag, zero otherwise

                        _a_r_g_c, _a_r_g_v the whole argument list

                        _o_p_t_i_n_d pointer to the index in argv where the flag is

                        _o_p_t_a_r_g pointer to the index in argv[*optind] where the
                        flag name starts

                        _d_a_t_a application specific data

                        You can modify _*_o_p_t_i_n_d, and _*_o_p_t_a_r_g, but to do this
                        correct you (more or less) have to know about the in-
                        ner workings of getarg.

                        You can skip parts of arguments by increasing _*_o_p_t_a_r_g
                        (you could implement the --zz_3 set of flags from ggzziipp
                        with this), or whole argument strings by increasing
                        _*_o_p_t_i_n_d (let's say you want a flag --cc _x _y _z to specify
                        a coordinate); if you also have to set _*_o_p_t_a_r_g to a
                        sane value.

                        The collect function should return one of
                        ARG_ERR_NO_MATCH, ARG_ERR_BAD_ARG, ARG_ERR_NO_ARG,
                        ENOMEM on error, zero otherwise.

                        For your convenience there is a function,
                        ggeettaarrgg__ooppttaarrgg(), that returns the traditional argument
                        string, and you pass it all arguments, sans data, that
                        where given to the collection function.

                        Don't use this more this unless you absolutely have
                        to.

     Option parsing is similar to what getopt uses. Short options without ar-
     guments can be compressed (--xxyyzz is the same as --xx --yy --zz), and short op-
     tions with arguments take these as either the rest of the argv-string or
     as the next option (--oo_f_o_o, or --oo _f_o_o).

     Long option names are prefixed with -- (double dash), and the value with
     a = (equal), ----ffoooo==_b_a_r. Long option flags can either be specified as they
     are (----hheellpp), or with an (boolean parsable) option (----hheellpp==_y_e_s,
     ----hheellpp==_t_r_u_e, or similar), or they can also be negated (----nnoo--hheellpp is the
     same as ----hheellpp==no), and if you're really confused you can do it multiple
     times (----nnoo--nnoo--hheellpp==_f_a_l_s_e, or even ----nnoo--nnoo--hheellpp==_m_a_y_b_e).

EEXXAAMMPPLLEE
     #include <stdio.h>
     #include <string.h>
     #include <getarg.h>

     char *source = "Ouagadougou";
     char *destination;
     int weight;
     int include_catalog = 1;
     int help_flag;

     struct getargs args[] = {
         { "source",      's', arg_string,  &source,
           "source of shippment", "city" },
         { "destination", 'd', arg_string,  &destination,
           "destination of shippment", "city" },
         { "weight",      'w', arg_integer, &weight,
           "weight of shippment", "tons" },
         { "catalog",     'c', arg_negative_flag, &include_catalog,
           "include product catalog" },
         { "help",        'h', arg_flag, &help_flag }
     };

     int num_args = sizeof(args) / sizeof(args[0]); /* number of elements in args */

     const char *progname = "ship++";

     int
     main(int argc, char **argv)
     {
         int optind = 0;
         if (getarg(args, num_args, argc, argv, &optind)) {
             arg_printusage(args, num_args, progname, "stuff...");
             exit (1);
         }
         if (help_flag) {
             arg_printusage(args, num_args, progname, "stuff...");
             exit (0);
         }
         if (destination == NULL) {
             fprintf(stderr, "%s: must specify destination\n", progname);
             exit(1);
         }
         if (strcmp(source, destination) == 0) {
             fprintf(stderr, "%s: destination must be different from source\n");
             exit(1);
         }
         /* include more stuff here ... */
         exit(2);
     }

     The output help output from this program looks like this:

     $ ship++ --help
     Usage: ship++ [--source=city] [-s city] [--destination=city] [-d city]
        [--weight=tons] [-w tons] [--no-catalog] [-c] [--help] [-h] stuff...
     -s city, --source=city      source of shippment
     -d city, --destination=city destination of shippment
     -w tons, --weight=tons      weight of shippment
     -c, --no-catalog            include product catalog

BBUUGGSS
     It should be more flexible, so it would be possible to use other more
     complicated option syntaxes, such as what ps(1),  and tar(1),  uses, or
     the AFS model where you can skip the flag names as long as the options
     come in the correct order.

     Options with multiple arguments should be handled better.

     Should be integreated with SL.

     It's very confusing that the struct you pass in is called getargS.

SSEEEE AALLSSOO
     getopt(3)

 ROKEN                        September 24, 1999                             4
