Redirect stdout to REPL

redirect.lisp

CL-USER> (multiple-value-bind (read write) (sb-unix:unix-pipe)
           (let ((read-stream (sb-sys:make-fd-stream read :buffering :line)))
             (sb-thread:make-thread (lambda ()
                                      (loop for line = (read-line read-stream nil nil)
                                            while line do (write-line line *standard-output*))))
             (sb-posix:dup2 write sb-sys:*stdout*)))
1
CL-USER> (progn (cffi:foreign-funcall "puts" :string "COME TO ME STDOUT!" :int)
                (cffi:foreign-funcall "fflush" :pointer (cffi:null-pointer) :int))
0
COME TO ME STDOUT!