Argp Example 2 (The GNU C Library)

#### 26.3.11.2 A Program Using Argp with Only Default Options ¶

This program doesn’t use any options or arguments, it uses argp to be compliant with the GNU standard command line format.

In addition to giving no arguments and implementing a ‘`--help`’ option, this example has a ‘`--version`’ option, which will put the given documentation string and bug address in the ‘`--help`’ output, as per GNU standards.

The variable `argp` contains the argument parser specification. Adding fields to this structure is the way most parameters are passed to `argp_parse`. The first three fields are normally used, but they are not in this small program. There are also two global variables that argp can use defined here, `argp_program_version` and `argp_program_bug_address`. They are considered global variables because they will almost always be constant for a given program, even if they use different argument parsers for various tasks.

    /* This program doesn’t use any options or arguments, but uses
       argp to be compliant with the GNU standard command line
       format.

       In addition to making sure no arguments are given, and
       implementing a –help option, this example will have a
       –version option, and will put the given documentation string
       and bug address in the –help output, as per GNU standards.

       The variable ARGP contains the argument parser specification;
       adding fields to this structure is the way most parameters are
       passed to argp_parse (the first three fields are usually used,
       but not in this small program).  There are also two global
       variables that argp knows about defined here,
       ARGP_PROGRAM_VERSION and ARGP_PROGRAM_BUG_ADDRESS (they are
       global variables because they will almost always be constant
       for a given program, even if it uses different argument
       parsers for various tasks). */

    #include <stdlib.h>
    #include <argp.h>

    const char *argp_program_version =
      "argp-ex2 1.0";
    const char *argp_program_bug_address =
      "<bug-gnu-utils@gnu.org>";

    /* Program documentation. */
    static char doc[] =
      "Argp example #2 -- a pretty minimal program using argp";

    /* Our argument parser.  The options, parser, and
       args_doc fields are zero because we have neither options or
       arguments; doc and argp_program_bug_address will be
       used in the output for ‘--help’, and the ‘--version’
       option will print out argp_program_version. */
    static struct argp argp = { 0, 0, 0, doc };

    int
    main (int argc, char **argv)
    {
      argp_parse (&argp, argc, argv, 0, 0, 0);
      exit (0);
    }