2.3.18 int strncmp_P
int strncmp_P(const char *, const char *, size_t) __ATTR_PURE__
The strncmp_P() function is similar to strcmp_P() except it only compares the first (at most) n characters of s1 and s2.
Remember:
The strncmp_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.