int strncasecmp_P(const char *, const char *, size_t) __ATTR_PURE__
The strncasecmp_P() function is similar to strcasecmp_P(), except it only compares the first n characters of s1.
The strncasecmp_P() function returns an integer less than, equal to, or greater than zero if s1 (or the first n bytes thereof) is found, respectively, to be less than, to match, or be greater than s2. A consequence of the ordering used by strncasecmp_P() is that if s1 is an initial substring of s2, then s1 is considered to be "less than" s2.