unbuffered keyboard input in LISP?

Is there a standard way to support unbuffered keyboard input in Common LISP, supported by all Common LISP interpreters?

So far I found something in the 'clisp' interpreter which comes with some nice unbuffered keyboard input macros.  I wrote a readline function:

(defun readline ()
 (ext:with-keyboard
  (let ((rdlinstring ""))
    (loop
     (setq char (read-char ext:*keyboard-input*))
     (setq key (or (ext:char-key char) (character char)))
     (setq rdlinstring (concatenate 'string rdlinstring (string key)))
     (write-string (string key))
     (when (eql key #\Return)
       (return rdlinstring))))))


But this doesn't work in CMUCL or SBCL.  I think anything that exists in an ext: package in one interpreter isn't guaranteed to exist in an ext: package in another interpreter (since ext: isn't Common LISP standard, but implementation-specific extensions).

Ummm, so... is there a STANDARD way to get unbuffered keyboard input in Common LISP that's guaranteed to work properly across all implementations that are standards-compliant?

use stty