The argument Fa optionp is a pointer to a pointer to the string. The argument Fa tokens is a pointer to a NULL -terminated array of pointers to strings.
The Fn getsubopt function returns the zero-based offset of the pointer in the Fa tokens array referencing a string which matches the first token in the string, or, -1 if the string contains no tokens or Fa tokens does not contain a matching string.
If the token is of the form ``name=value'', the location referenced by Fa valuep will be set to point to the start of the ``value'' portion of the token.
On return from Fn getsubopt , Fa optionp will be set to point to the start of the next token in the string, or the null at the end of the string if no more tokens are present. The external variable Fa suboptarg will be set to point to the start of the current token, or NULL if no tokens were present. The argument Fa valuep will be set to point to the ``value'' portion of the token, or NULL if no ``value'' portion was present.
char *tokens[] = {
#define ONE 0
"one",
#define TWO 1
"two",
NULL
};
...
extern char *optarg, *suboptarg;
char *options, *value;
while ((ch = getopt(argc, argv, "ab:")) != -1) {
switch(ch) {
case 'a':
/* process ``a'' option */
break;
case 'b':
options = optarg;
while (*options) {
switch(getsubopt(&options, tokens, &value)) {
case ONE:
/* process ``one'' sub option */
break;
case TWO:
/* process ``two'' sub option */
if (!value)
error("no value for two");
i = atoi(value);
break;
case -1:
if (suboptarg)
error("illegal sub option %s",
suboptarg);
else
error("missing sub option");
break;
}
break;
}