Returns either a character from the stream, an :EOF if the end-of-file is reached, or nil if no input is currently available.
The generic function stream-read-char-no-hang implements read-char-no-hang . It returns either a character read from the stream, an :EOF if end-of-file is reached, or nil if no input is available. The default method provided by fundamental-character-input-stream simply calls stream-read-char which is sufficient for file streams, but interactive streams should define their own method.