names=world_writable?
visibility=public
kind=defined

--- world_writable? -> Fixnum | nil

If stat is writable 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("/tmp").world_writable?         # => 511
   sprintf("%o", m)                              # => "777"

