names=world_readable?
visibility=public
kind=defined

--- world_readable? -> Fixnum | nil

If stat is readable by others, returns an integer representing
the file permission bits of stat. Returns nil otherwise. The
meaning of the bits is platform dependent; on Unix systems, see
stat(2).

   m = File.stat("/etc/passwd").world_readable?  # => 420
   sprintf("%o", m)                              # => "644"

