(defun eshell-append-history ()
  "Call `eshell-write-history' with the `append' parameter set to `t'."
  (when eshell-history-ring
    (let ((newest-cmd-ring (make-ring 1)))
      (ring-insert newest-cmd-ring (car (ring-elements eshell-history-ring)))
      (let ((eshell-history-ring newest-cmd-ring))
        (eshell-write-history eshell-history-file-name t)))))