getopt.h

/* Declarations for getopt.
   Copyright (C) 1989, 90, 91, 92, 93, 94 Free Software Foundation, Inc.

This file is part of the GNU C Library.  Its master source is NOT part of
the C library, however.  The master source lives in /gd/gnu/lib.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#ifndef _GETOPT_H
#define _GETOPT_H 1

#ifdef __cplusplus
extern "C" {
#endif

/* For communication from `getopt' to the caller.
   When `getopt' finds an option that takes an argument,
   the argument value is returned here.
   Also, when `ordering' is RETURN_IN_ORDER,
   each non-option ARGV-element is returned here.  */

extern char *optarg;

/* Index in ARGV of the next element to be scanned.
   This is used for communication to and from the caller
   and for communication between successive calls to `getopt'.

   On entry to `getopt', zero means this is the first call; initialize.

   When `getopt' returns EOF, this is the index of the first of the
   non-option elements that the caller should itself scan.

   Otherwise, `optind' communicates from one call to the next
   how much of ARGV has been scanned so far.  */

extern int optind;

/* Callers store zero here to inhibit the error message `getopt' prints
   for unrecognized options.  */

extern int opterr;

/* Set to an option character which was unrecognized.  */

extern int optopt;

/* Describe the long-named options requested by the application.
   The LONG_OPTIONS argument to getopt_long or getopt_long_only is a vector
   of `struct option' terminated by an element containing a name which is
   zero.

   The field `has_arg' is:
   no_argument  (or 0) if the option does not take an argument,
   required_argument (or 1) if the option requires an argument,
   optional_argument  (or 2) if the option takes an optional argument.

   If the field `flag' is not NULL, it points to a variable that is set
   to the value given in the field `val' when the option is found, but
   left unchanged if the option is not found.

   To have a long-named option do something other than set an `int' to
   a compiled-in constant, such as set a value from `optarg', set the
   option's `flag' field to zero and its `val' field to a nonzero
   value (the equivalent single-letter option character, if there is
   one).  For long options that have a zero `flag' field, `getopt'
   returns the contents of the `val' field.  */

struct option
{
#if defined (__STDC__) && __STDC__
  const char *name;
#else
  char *name;
#endif
  /* has_arg can't be an enum because some compilers complain about
     type mismatches in all the code that assumes it is an int.  */
  int has_arg;
  int *flag;
  int val;
};

/* Names for the values of the `has_arg' field of `struct option'.  */

#define no_argument  0
#define required_argument 1
#define optional_argument 2

#if defined (__STDC__) && __STDC__
#ifdef __GNU_LIBRARY__
/* Many other libraries have conflicting prototypes for getopt, with
   differences in the consts, in stdlib.h.  To avoid compilation
   errors, only prototype getopt for the GNU C library.  */
extern int getopt (int argc, char *const *argv, const char *shortopts);
#else /* not __GNU_LIBRARY__ */
extern int getopt ();
#endif /* __GNU_LIBRARY__ */
extern int getopt_long (int argc, char *const *argv, const char *shortopts,
          const struct option *longopts, int *longind);
extern int getopt_long_only (int argc, char *const *argv,
        const char *shortopts,
               const struct option *longopts, int *longind);

/* Internal only.  Users should not call this directly.  */
extern int _getopt_internal (int argc, char *const *argv,
        const char *shortopts,
               const struct option *longopts, int *longind,
        int long_only);
#else /* not __STDC__ */
extern int getopt ();
extern int getopt_long ();
extern int getopt_long_only ();

extern int _getopt_internal ();
#endif /* __STDC__ */

#ifdef __cplusplus
}
#endif

#endif /* _GETOPT_H */

 

Example 1 (using getopt)

#include <stdio.h> /* for printf */
#include <stdlib.h> /* for exit */
#include <unistd.h> /* for getopt */
int main (int argc, char **argv) {
    int c;
    int digit_optind = 0;
    int aopt = 0, bopt = 0;
    char *copt = 0, *dopt = 0;
    while ( (c = getopt(argc, argv, "abc:d:012")) != -1) {
        int this_option_optind = optind ? optind : 1;
        switch (c) {
        case '0':
        case '1':
        case '2':
            if (digit_optind != 0 && digit_optind != this_option_optind)
              printf ("digits occur in two different argv-elements.\n");
            digit_optind = this_option_optind;
            printf ("option %c\n", c);
            break;
        case 'a':
            printf ("option a\n");
            aopt = 1;
            break;
        case 'b':
            printf ("option b\n");
            bopt = 1;
            break;
        case 'c':
            printf ("option c with value '%s'\n", optarg);
            copt = optarg;
            break;
        case 'd':
            printf ("option d with value '%s'\n", optarg);
            dopt = optarg;
            break;
        case '?':
            break;
        default:
            printf ("?? getopt returned character code 0%o ??\n", c);
        }
    }
    if (optind < argc) {
        printf ("non-option ARGV-elements: ");
        while (optind < argc)
            printf ("%s ", argv[optind++]);
        printf ("\n");
    }
    exit (0);
}

[edit] Example 2 (using GNU long option variation)

#include <stdio.h> /* for printf */
#include <stdlib.h> /* for exit */
#include <getopt.h> /* for getopt_long; standard getopt is in unistd.h */
int main (int argc, char **argv) {
    int c;
    int digit_optind = 0;
    int aopt = 0, bopt = 0;
    char *copt = 0, *dopt = 0;
    static struct option long_options[] = {
        {"add", 1, 0, 0},
        {"append", 0, 0, 0},
        {"delete", 1, 0, 0},
        {"verbose", 0, 0, 0},
        {"create", 1, 0, 'c'},
        {"file", 1, 0, 0},
        {NULL, 0, NULL, 0}
    };
    int option_index = 0;
    while ((c = getopt_long(argc, argv, "abc:d:012",
                 long_options, &option_index)) != -1) {
        int this_option_optind = optind ? optind : 1;
        switch (c) {
        case 0:
            printf ("option %s", long_options[option_index].name);
            if (optarg)
                printf (" with arg %s", optarg);
            printf ("\n");
            break;
        case '0':
        case '1':
        case '2':
            if (digit_optind != 0 && digit_optind != this_option_optind)
              printf ("digits occur in two different argv-elements.\n");
            digit_optind = this_option_optind;
            printf ("option %c\n", c);
            break;
        case 'a':
            printf ("option a\n");
            aopt = 1;
            break;
        case 'b':
            printf ("option b\n");
            bopt = 1;
            break;
        case 'c':
            printf ("option c with value '%s'\n", optarg);
            copt = optarg;
            break;
        case 'd':
            printf ("option d with value '%s'\n", optarg);
            dopt = optarg;
            break;
        case '?':
            break;
        default:
            printf ("?? getopt returned character code 0%o ??\n", c);
        }
    }
    if (optind < argc) {
        printf ("non-option ARGV-elements: ");
        while (optind < argc)
            printf ("%s ", argv[optind++]);
        printf ("\n");
    }
    exit (0);
}