dir(string) returns a set of all strings with all entries in the specified directory. Also . and .. are contained.
dir() returns a set of all entries in the current directory of this process. It is the same as dir(".").
dir(adir, pattern) returns a set of all entries in adir that match pattern. The pattern is a shell-like globbing pattern and may contain the special characters * and ? for a sequence of arbitrary character or one arbitrary character resp.