Note that as usual, the output is buffered, so it may need to be flushed either by closing the stream, by writing again or by using flush/1.
Success:
      display(output, 3.0).                % displays 3.0
      set_stream(a,output), display(a,hi). % displays hi
      [eclipse]: open(file1,update,S), display(S, X+2), close(S).
      X = _72
      S = 6
      yes.
      [eclipse]: sh('cat file1').
      +(_98, 2)
      yes.
Error:
      display(S, a(b,c)).        (Error 4).
      display("string", a(b,c)). (Error 5).
      display(9, X=2).           (Error 192). % stream not open
      display(atom, X=2).        (Error 193).