funflush causes any buffered data to be discarded.
Unlike fflush [see
fclose(S-osr5)],
funflush does not
write any pending data for output streams and does not attempt to synchronize
the underlying file offset.
It is principally intended for handling streams connected
to terminals as part of interrupt processing.
If stream is a null pointer, funflush acts
on all open stdio streams.
stream remains open.