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    GETOPT(3)           Linux Programmer's Manual           GETOPT(3)

    NAME
           getopt - Read command line options

    SYNOPSIS
           #include <unistd.h>

           int getopt(int argc, char * const argv[],
                      const char *optstring);

           extern char *optarg;
           extern int optind, opterr, optopt;

           #include <getopt.h>

           int getopt_long(int argc, char * const argv[],
                           const char *shortopts,
                           const struct option *longopts, int longind);

    DESCRIPTION
           The  getopt()  function parses the command line arguments.
           Its arguments argc and argv are  the  argument  count  and
           array  as passed to the main() function on program invoca-
           tion.  optstring is a list of available option characters.
           If  such  a  character  is followed by a colon, the option
           takes an argument, which is placed in optarg.

           The external variable optind is  the  index  of  the  next
           array  element  of argv[] to be processed; it communicates
           from one call of getopt() to the  next  which  element  to
           process.

           The getopt_long() function works like getopt() except that
           it also accepts long options, started out by  two  dashes.
           If these take values, it is either in the form --arg=value
           or --arg value.  It takes the  additional  arguments  lon-
           gopts  which is a pointer to the first element of an array
           of struct option declared in <getopt.h> as

              struct option {
                  const char *name;
                  int has_arg;
                  int *flag;
                  int val;
              };

              The meaning of the different fields are:

           name   is the name of the long option.

           has_arg
                  is a boolean value which should be set  to  nonzero
                  if the long option takes a value.

           flag   determines   the   return  value  if  getopt_long()

    GNU                       April 25, 1993                        1

    GETOPT(3)           Linux Programmer's Manual           GETOPT(3)

                  returns a value for a long option; if  it  is  non-
                  zero,  zero is returned as a function value, other-
                  wise val.

           val    determines the value to return if flag is zero.

           The last element of  the  array  has  to  be  filled  with
           zeroes.

           The  option_index  points  to the index of the long option
           relative to longopts.

    RETURN VALUE
           The getopt() function returns the option character if  the
           option  was found successfully, ':' if there was a missing
           parameter for one of  the  options,  '?'  for  an  unknown
           option character and -1 for the end of the option list.

    EXAMPLE
           The  following  example  program,  from  the  source code,
           illustrates the use of getopt_long() with most of its fea-
           tures.

           #include <stdio.h>

           int
           main (argc, argv)
                int argc;
                char **argv;
           {
             int c;
             int digit_optind = 0;

             while (1)
               {
                 int this_option_optind = optind ? optind : 1;
                 int option_index = 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},
                {0, 0, 0, 0}
                 };

                 c = getopt_long (argc, argv, "abc:d:012",
                            long_options, &option_index);
                 if (c == -1)
                break;

                 switch (c)

    GNU                       April 25, 1993                        2

    GETOPT(3)           Linux Programmer's Manual           GETOPT(3)

                {
                case 0:
                  printf ("option %s", long_options[option_index].name);
                  if (optarg)
                    printf (" with arg %s", optarg);
                  printf ("0);
                  break;

                case '0':
                case '1':
                case '2':
                  if (digit_optind != 0 && digit_optind != this_option_optind)
                    printf ("digits occur in two different argv-elements.0);
                  digit_optind = this_option_optind;
                  printf ("option %c0, c);
                  break;

                case 'a':
                  printf ("option a0);
                  break;

                case 'b':
                  printf ("option b0);
                  break;

                case 'c':
                  printf ("option c with value `%s'0, optarg);
                  break;

                case 'd':
                  printf ("option d with value `%s'0, optarg);
                  break;

                case '?':
                  break;

                default:
                  printf ("?? getopt returned character code 0%o ??0, c);
                }
               }

             if (optind < argc)
               {
                 printf ("non-option ARGV-elements: ");
                 while (optind < argc)
                printf ("%s ", argv[optind++]);
                 printf ("0);
               }

             exit (0);
           }

    BUGS
           This manpage is confusing.

    GNU                       April 25, 1993                        3

    GETOPT(3)           Linux Programmer's Manual           GETOPT(3)

    CONFORMS TO
           getopt() :
                  POSIX.1

    GNU                       April 25, 1993                        4

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