int strcasecmp(const char *, const char *) __ATTR_PURE__
The strcasecmp() function compares the two strings
s1 and s2, ignoring
the case of the characters.
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.