The user-stream hook is, if defined, called during
SP_initialize(). It has the following prototype:
SP_stream *user_stream_hook(int which)
If the hook is not defined, SICStus will attempt to open the standard TTY/console versions of these streams. If they are unavailable (such as for windowed executables under Windows), the result is undefined.
It is called three times, one for each stream. The
argument indicates which stream it is called for. The value
which is one of:
The hook should return a standard SICStus I/O stream, as described in Defining a New Stream.