(defun diff-strings (string1 string2)
  (let (realpath1 realpath2 fullpath return)
   (uiop:with-temporary-file (:pathname path1 :keep t :directory "/tmp")
     (uiop:with-temporary-file (:pathname path2 :keep t :directory "/tmp")
       (with-open-file (file1 path1 :direction :output)
         (with-open-file (file2 path2 :direction :output)
           (setq realpath1 path1
                 realpath2 path2)
           (princ string1 file1)
           (princ string2 file2)))))
   (setq fullpath (list "/usr/bin/diff" (uiop:native-namestring realpath1) (uiop:native-namestring realpath2)))
   (setq return (uiop:run-program fullpath
                                  :output :string
                                  :ignore-error-status t))
   (uiop:delete-file-if-exists realpath1)
   (uiop:delete-file-if-exists realpath2)
   return))