以前从网站上拉下来一个，不过使用了post-command-hook，参考修改了一下，能够比较及时显示。

;;;Emacs title bar to reflect file name

(defun frame-title-string ()

"Return the file name of current buffer, using ~ if under home directory"

(let

((fname (or

(buffer-file-name (current-buffer))

(buffer-name))))

;;let body

(when (string-match (getenv "HOME") fname)

(setq fname (replace-match "~" t t fname)) )

fname))

;;; Title = 'system-name File: foo.bar'

(setq frame-title-format '("" system-name " File: "(:eval (frame-title-string))))