External Solver Output and Log

## 9.7 External Solver Output and Log

The external solver's output can be controlled using:

`lp_set(SolverChannel, +(Stream))`
  Send output from SolverChannel to the ECLiPSe I/O stream Stream.
`lp_set(SolverChannel, -(Stream))`
  Stop sending output from SolverChannel to the ECLiPSe I/O stream Stream.

SolverChannel is one of `result_channel, error_channel, warning_channel, log_channel`, and Stream is an ECLiPSe stream identifier (e.g. `output`, or the result of an open/3 operation). By default, `error_channel` is directed to ECLiPSe's `error` stream, `warning_channel` to `warning_output` stream, while `result_channel` and `log_channel` are suppressed. To see the output on these channels, do for instance

    :- lp_set(result_channel, +output), lp_set(log_channel, +log_output).

Similarly, to create a log file:

    :- open("mylog.log", write, logstream), lp_set(log_channel, +logstream).

and to stop logging:

    :- lp_set(log_channel, -logstream), close(logstream).