How to force Emacs to save even if it thinks (no changes need to be saved)

Question

This happens to me all the time:

• I have a file open in emacs,
• I save it ('save-buffer),
• the file changes on disk (or get's deleted, moved, etc.)
• but I want it back, so I try to save again in emacs ('save-buffer) and instead of saving it says "(no changes need to be saved)" and does nothing.

Is there a different function, or a setting, that I can use to force emacs to save?

Answer 1

You can save as, with C-x C-w. That should save unconditionally. You can also just type a space then backspace over it. Emacs is smart enough to realize that if you undo everything you've done so far the buffer has no changes, but if you make changes and then manually reverse them it will consider the buffer to have been changed.

Answer 2

You can mark the current buffer as modified using the Emacs-Lisp function not-modified with a prefix arg, bound to:

C-u M-~

The answer above won't work if you don't call the new function directly. If you want to seamlessly change emacs saving behavior. The best solution is to create an advice:

(defadvice save-buffer (before save-buffer-always activate)
  "always save buffer"
  (set-buffer-modified-p t))

Answer 3

Wrap a function around save-buffer that marks the buffer modified first:

(defun save-buffer-always ()
  "Save the buffer even if it is not modified."
  (interactive)
  (set-buffer-modified-p t)
  (save-buffer))

Answer 4

As a slight alternative to scottfrazer's answer:

(defun my-save-buffer-always-sometimes (prefix)
  "Save the buffer even if it is not modified."
  (interactive "P")
  (when prefix
    (set-buffer-modified-p t))
  (save-buffer))

This was you can force it when you want to with a prefix (C-u C-x C-s) but not unnecessarily change a file otherwise. The last modified timestamp is very useful (e.g. source code control) that it seems a shame to change it arbitrarily. YMMV, of course.