Forces the buffered output of the stream Stream (defaults to the current output stream) to be sent to the associated device.
stream_object, must be ground
A valid Prolog stream, defaults to the current output stream.
Sends the current buffered output of an output stream Stream to the actual output device, which is usually a disk or a tty device.
Stream errors (see ref-iou-sfh-est), plus:
An error occurred in flushing out the buffered output.