clear-input &optional input-stream → nil

input-stream — an input stream designator. The default is standard input.

Clears any available input from input-stream.

If clear-input does not make sense for input-stream, then clear-input does nothing.

;; The exact I/O behavior of this example might vary from implementation 
;; to implementation depending on the kind of interactive buffering that 
;; occurs.  (The call to SLEEP here is intended to help even out the 
;; differences in implementations which do not do line-at-a-time buffering.) 

(defun read-sleepily (&optional (clear-p nil) (zzz 0)) 
  (list (progn (print '>) (read)) 
        ;; Note that input typed within the first ZZZ seconds 
        ;; will be discarded. 
        (progn (print '>) 
               (if zzz (sleep zzz)) 
               (print '>>) 
               (if clear-p (clear-input)) 
               (read)))) 

(read-sleepily) 
⊳ > 10 
⊳ > 
⊳ >> 20 
→ (10 20) 

(read-sleepily t) 
⊳ > 10 
⊳ > 
⊳ >> 20 
→ (10 20) 

(read-sleepily t 10) 
⊳ > 10 
⊳ > 20  ; Some implementations won't echo typeahead here. 
⊳ >> 30 
→ (10 30)

The input-stream is modified.

*standard-input*

Should signal an error of type type-error if input-stream is not a stream designator.

clear-output