how to parse from command line arguements in yacc ?

of course i undefined input in both lex & yacc and then wrote

int input(void)
{
printf("in input\n:");
char c;
if(target >  limit)
return 0;
if((c = target[0][offset++]) != '\0')
return (c);
target++;
offset =0;
return (' ');
}

where target contains the command line arguements. But only the standard input is getting excueted how to make dis input function get executed.