anchor.diff:      (t (princ-to-string argument))))
   
   (defun run (command &rest arguments)
  +  "Run shell-command COMMAND with ARGUMENTS as arguments. Searches the
  +PATH environment for the right command to run. Arguments are converted
  +to strings with STRINGIFY-COMMAND-ARGUMENT. If the command exits with
  +nonzero status, signals an error."
     (let ((process (run-program command (mapcar #'stringify-command-argument arguments)
                                 :search t
                                 :wait t
  
positive.code:                (error condition))))))))
  
  (defmacro in-temporary-directory (template-pathname &body body)
    `(call-in-temporary-directory ,template-pathname (lambda () ,@body)))
  
  (defun copy-file (from to)
    (run "cp" (native (truename from)) (native to)))
  
negative.code: 
  (defvar *command-output* (make-synonym-stream '*standard-output*))
  
  ;;; FIXME: Should be a generic function.
  (defun stringify-command-argument (argument)
    "Convert ARGUMENT to a string suitable for passing to RUN."
    (typecase argument
      (string argument)
      (pathname (native-namestring argument))
  