[함수] getopt, getopt_long

원글(이글루): 2009-12-29 20:33:06

보통 -v 형태의 옵션을 처리할때 사용하는 함수

■ 사용방법
#include <unistd.h>

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

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

#define _GNU_SOURCE

#include <getopt.h>

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

int getopt_long_only(int argc, char * const argv[],
           const char *optstring,
           const struct option *longopts, int *longindex);

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

□  name
-  long option의 이름
□ 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, or optional_argument (or 2) if the option takes an optional argument.
□ flag
- specifies how results are returned for a long option. If flag is NULL, then getopt_long() returns val. (For example, the calling program may set val to the equivalent short option character.) Otherwise, getopt_long() returns 0, and flag points to a variable which is set to val if the option is found, but left unchanged if the option is not found.
□ val
- is the value to return, or to load into the variable pointed to by flag

■ 예제
#include <stdio.h>     /* for printf */
#include <stdlib.h>    /* for exit */
#include <getopt.h>

int
main (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) {
        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");
            break;

        case 'b':
            printf ("option b\n");
            break;

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

        case 'd':
            printf ("option d with value `%s'\n", 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);
}