string-equal

(string-equal string1 string2 &key start1 end1 start2 end2)

Compares two strings character by character ignoring case and returns t when they match, nil otherwise. Case folding follows ASCII rules, so "ABC" and "abc" are equal. Use string= for a case-sensitive comparison. :start1/:end1/:start2/:end2 bound the substrings actually compared.