#include <string.h> int memicmp(const void *s1, const void *s2, size_t num);
This function compares two regions of memory, at s1 and s2, for num bytes, disregarding case.
Zero if they're the same, nonzero if different, the sign indicates "order".
if (memicmp(arg, "-i", 2) == 0) /* '-I' or '-include' etc. */ do_include();