Command line arguments

cli.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char *argv[])
{
    int a, b, len, chr;

    for (a = 1; a < argc; ++a) {
        switch ((int)argv[a][0]) {
            case '\\':
            case '/':
            case '-':
                // Scan through the passed options.
                len = strlen(argv[a]);
                for (b = 1; b < len; ++b) {
                    chr = (int)argv[a][b];
                    switch (chr) {
                        case '?':
                        case 'h':
                        case 'H':
                            printf("help is on the way.\n");
                            break;
                        default:
                            printf("something else\n");
                            break;
                    }
                }
                break;
            default:
                printf("string: %s\n", argv[a]);
                break;
        }
    }
    return 0;
}

I tried to abstract the first switch to a function, but that doesn't work... what am I doing wrong?

int main(int argc, char *argv[])
{
    int a, b, len, chr;

    for (a = 1; a < argc; ++a) {
        printf("is option: %s\n", is_option(argv[a]));
        if (is_option(argv[a])) {
            // Scan through the passed options.
            len = strlen(argv[a]);
            for (b = 1; b < len; ++b) {
                chr = (int)argv[a][b];
                switch (chr) {
                    case '?':
                    case 'h':
                    case 'H':
                        printf("help is on the way.\n");
                        break;
                    default:
                        printf("something else\n");
                        break;
                }
            }
        }
        else {
            printf("string %s\n", argv[a]);
        }
    }
    return 0;
}

int is_option(int arg) {
    switch ((int)arg[0]) {
        case '\\':
        case '/':
        case '-':
            return 1;
        default:
            return 0;
    }
}

test.c: In function 'is_option':
test.c:8:21: error: subscripted value is neither array nor pointer nor vector
     switch ((int)arg[0]) {
                     ^
test.c: In function 'main':
test.c:23:45: warning: passing argument 1 of 'is_option' makes integer from pointer without a cast [-Wint-conversion]
         printf("is option: %s\n", is_option(argv[a]));
                                             ^
test.c:7:5: note: expected 'int' but argument is of type 'char *'
 int is_option(int arg) {
     ^
test.c:24:23: warning: passing argument 1 of 'is_option' makes integer from pointer without a cast [-Wint-conversion]
         if (is_option(argv[a])) {
                       ^
test.c:7:5: note: expected 'int' but argument is of type 'char *'
 int is_option(int arg) {
     ^