The strcasecmp and strncasecmp functions compare the null-terminated strings s1 and s2.
The strncasecmp compares at most len characters.
The strcasecmp and strncasecmp return an integer greater than, equal to, or less than 0, according as s1 is lexicographically greater than, equal to, or less than s2 after translation of each corresponding character to lower-case. The strings themselves are not modified. The comparison is done using unsigned characters, so that '\200' is greater than \0.
bcmp(3), memcmp(3), strcmp(3), strcoll(3), strxfrm(3), tolower(3)