lispdoc - results for read-char-no-hang

(read-char-no-hang &optional (stream *standard-input*) (eof-error-p t)
 eof-value recursive-p)
 Mentioned in:
CLtL2 - 22.2.1. Input from Character Streams
HyperSpec - Function READ-CHAR-NO-HANG
Successful Lisp - chapter19
(trivial-gray-streams:stream-read-char-no-hang stream)
Function: This is used to implement READ-CHAR-NO-HANG. It returns either a character, or NIL if no input is currently available, or :EOF if end-of-file is reached. The default method provided by FUNDAMENTAL-CHARACTER-INPUT-STREAM simply calls STREAM-READ-CHAR; this is sufficient for file streams, but interactive streams should define their own method.