(defun c:sdfcorrect (/ filename file line lines)
  (princ "\nSDFCORRECT (c) 1997 by Dietmar Rudolph, CR/LF GmbH, Essen/Germany")
  (cond ((not (setq filename (getfiled "SDF file to correct" "" "txt" 0))))
        ((not (setq file (open filename "r")))
           (alert (strcat filename "\nNo such file!")))
        (t (setq lines '())
           (while (setq line (read-line file))
              (setq lines (cons line lines)))
           (close file)
           (cond ((not (setq file (open filename "w")))
                     (alert (strcat filename "\nWrite protected!")))
                 (t (foreach line (reverse lines)
                       (write-line line file))
                    (close file))
           ))
  )
  (princ)
)