strcasecmp
Converts all characters to lowercase and then compares two strings
#include <string.h> int strcasecmp ( const char *s1, const char *s2);
Returns zero if the two strings match. Otherwise, it returns an integer less than or greater than zero, depending on whether s1 is lexicographically less than or greater than s2.
strcasecmp is identical to strcmp, except that the characters of each string are converted to lowercase before comparison.
Each character is treated as if it is of type unsigned char, and NULL pointers are treated as pointers to empty strings.