2.2.17 int strcasecmp
int strcasecmp(const char *, const char *) __ATTR_PURE__
The strcasecmp() function compares the two strings s1 and s2, ignoring the case of the characters.
Remember:
The strcasecmp() function returns an integer less than, equal to, or greater than zero if s1 is found, respectively, to be less than, to match, or be greater than s2. A consequence of the ordering used by strcasecmp() is that if s1 is an initial substring of s2, then s1 is considered to be "less than" s2.