clear-output

(clear-output &optional stream)

Discards whatever the designated output stream has buffered but not yet written, and returns nil. No backend buffers output in a way a program could throw away -- a write reaches the underlying sink as it is made -- so this validates its stream designator and does nothing else. It exists because the Gray protocol names stream-clear-output, which a portable stream class implements: on a Gray instance the call reaches that method.