This code works when launched like this: clisp test.lisp

;;contents of test.lisp file
(defun wtof (filename text)
  "Append TEXT to the file specified by FILENAME."
  (with-open-file (stream filename :direction :output :element-type 'character :if-does-not-exist :create :if-exists :append)
    (write-string text stream)))

(wtof "test.c" "/* hello world */")

But I’d like to use slime to type last line (wtof "test.c" "/* hello world */") and have things written into test.c file. Is that possible? Slime gives an error.