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I recently had a Sublime Text user try out Emacs for a while, and he was interested in getting the same auto-save behavior in Emacs.

Basically, he wanted all buffers to be saved whenever the frame lost focus (really saved, not just backed-up). This includes when switching windows to a completely different application.

I could not find any event that was triggered when switching to a different application. Is there such an event or is there another way to achieve the same behavior?

Note a time based solution was not satisfactory, and neither was the default auto backup behavior. He specifically wanted the buffers to be saved (as in save-buffer) for all files.

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5 Answers 5

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Unfortunately, this exact behavior isn't possible in Emacs <= 24.3, but you can save on window/buffer change using defadvice (as detailed on bbatsov's blog):

(defadvice switch-to-buffer (before save-buffer-now activate) (when (and buffer-file-name (buffer-modified-p)) (save-buffer))) (defadvice other-window (before other-window-now activate) (when (and buffer-file-name (buffer-modified-p)) (save-buffer)))

In Emacs 24.4, you will also be able to save on frame focus loss thanks to the new focus hooks: (add-hook 'focus-out-hook 'save-buffer) (to save the active buffer) or (add-hook 'focus-out-hook (lambda () (save-some-buffers t))) (to save all open buffers).

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    Could you expand a bit on the defadvice version, in case the blog post goes down or something? Thanks! Commented Sep 25, 2014 at 18:35
  • Unfortunately, that solution on saves the currently visible buffer, not all buffers. Commented Sep 25, 2014 at 18:45
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    @b4hand: Sorry, didn't realize that's what you wanted. Answer updated. Commented Sep 25, 2014 at 18:47
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    @shosti By the way, thanks for finding that link to bbatsov's blog for me. I had actually found that solution before, but couldn't find it again. I was going to include that as one of the non-working solutions in my question. Commented Sep 25, 2014 at 20:24
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    I like doing it this way to avoid trashing the minibuffer (pardon the formatting): (add-hook 'focus-out-hook (lambda () (flet ((message (format &rest args) nil)) (save-some-buffers t)))) Commented Oct 16, 2014 at 6:19
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There is focus-autosave-mode now. It's available via MELPA. Why not give it a chance to do the hacking for you‽

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  • Hi, How it work? I've install it but it don't seems to work. Commented Apr 8, 2017 at 2:46
  • @AsmeJust, I don't use right now, try to ask on its issue tracker here: github.com/vifon/focus-autosave-mode.el/issues Commented Apr 8, 2017 at 21:50
  • Do you currently use an alternative or somethng like that? Commented Apr 10, 2017 at 7:10
  • No, I don't use anything like that right now. Commented Apr 10, 2017 at 12:03
  • But you still use Emacs, right? Commented Apr 10, 2017 at 19:03
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(add-to-list 'focus-out-hook (lambda () (save-some-buffers t nil)))

This will save all unsaved buffers visiting file, on emacs 24.4

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    Don't use add-to-list on a hook, use add-hook. shosti's answer already contains the correct form of this snippet. Commented Nov 10, 2014 at 23:17
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For wanderers who stumble on this, I use this form: 

(eval-when-compile (require 'cl-lib)) ;; [...] (add-hook 'focus-out-hook (lambda () (cl-letf (((symbol-function 'message) #'format)) (save-some-buffers t))))

The use of cl-letf keeps the annoying (No files need saving) messages from clogging your echo area.

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There is the super-save package described as:

super-save auto-saves your buffers, when certain events happen - e.g. you switch between buffers, an Emacs frame loses focus, etc. You can think of it as both something that augments and replaces the standard auto-save-mode.

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