strchr returns a zero-based index to the first occurrence of char. If char is not found NULL is returned. char can be given either as an integer ASCII value or a string, in which case the first character of that string is searched fo.
strchr('AbracadabrA','A')
-> 0 (Found as the first character).
strrchr('AbracadabrA',65)
-> 10 (Found as the eleventh character)