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

int getsubopt(char **opt, char *const *keys, char **val)
{
        char *s = *opt;
        int i;

        *val = NULL;
        *opt = strchr(s, ',');
        if (*opt) *(*opt)++ = 0;
        else *opt = s + strlen(s);

        for (i=0; keys[i]; i++) {
                size_t l = strlen(keys[i]);
                if (strncmp(keys[i], s, l)) continue;
                if (s[l] == '=')
                        *val = s + l + 1;
                else if (s[l]) continue;
                return i;
        }
        return -1;
}