See section 4.2 for an overview of supported character representations.
put(10).user and the 
cursor is not at the left margin.user. See also flush_output/[0,1].
end_of_file.update.[]).
This predicate is intended for efficient unbuffered copying and 
filtering of input coming from network connections or devices. It also 
enables the library library(pure_input), which processes 
input from files and streams using a DCG.
The following code fragment realises efficient non-blocking copying of data from an input to an output stream. The at_end_of_stream/1 call checks for end-of-stream and fills the input buffer. Note that the use of a get_code/2 and put_code/2 based loop requires a flush_output/1 call after each put_code/2. The copy_stream_data/2 does not allow for inspection of the copied data and suffers from the same buffering issues.
copy(In, Out) :-
        repeat,
            fill_buffer(In),
            read_pending_codes(In, Chars, Tail),
            \+ \+ ( Tail = [],
                    format(Out, '~s', [Chars]),
                    flush_output(Out)
                  ),
            (   Tail == []
            ->  !
            ;   fail
            ).