current_stream(File, Mode, Stream) succeeds if
Stream is a stream that is currently open on file File in mode
Mode, where Mode is either
append. None of the arguments need be initially instantiated.
This predicate is nondeterminate and can be used to backtrack through all
current_stream/3 ignores certain predefined streams, including
the initial values of the special streams for the standard input,
output, and error channels.
stream_property(Stream, Property) succeeds if
Stream is a currently open stream with property Property.
Predefined streams, like the three standard channels, are not ignored.