Recursive directory creation API

Right way: succeed if directory exists. Examples: GNU Coreutils, Common Lisp.

Wrong way: fail if directory exists. Example: Python.

I should think that if a recursive directory creator thinks that failure in the case of existence of the final directory in the series is an option, it should also fail if the parent exists, and so on, proceeding to fail in the case of the existence of ‘/’, when all else doesn't fail.