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Is there a way to force Emacs to automatically save the current file (if it is not already saved) after typing n characters (n is a number determined by the user).

Edit: After the comment of @Dan and the suggestion of @lawlist it seems that the solution below is less risky: 

   (setq auto-save-interval 10) ;;; n=10

    (defun force-backup-of-buffer ()
      (setq buffer-backed-up nil))

    (add-hook 'before-save-hook  'force-backup-of-buffer)

I should mention that the above solution is based on http://www.emacswiki.org/emacs/ForceBackups.

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    Some unsolicited advise (I know, hooray!): be cautious with automatic saves. You run the risk that accidental changes to the buffer (unintentional deletes, mis-keyed yanks, etc.) could trigger a save, which will overwrite your file. auto-save-mode gets you most of the way there without actually overwriting your file; it seems better to reserve the explicit save for human intervention. As an alternative, maybe consider a function that puts a message in the echo area every n characters such as "You've changed a lot of text, please consider saving!", which you can heed or ignore at will.
    – Dan ♦
    Commented Jan 31, 2015 at 12:06
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    @Dan thank you for the advice. You are right, I think I should use the build-in auto-save feature.
    – Name
    Commented Jan 31, 2015 at 14:50

1 Answer 1

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Emacs has an auto-save feature that can be adapted to suit your needs. You can customize auto-save-interval to determine how many characters:

auto-save-interval is a variable defined in `C source code'. Its value is 300

Documentation: Number of input events between auto-saves. Zero means disable autosaving due to number of characters typed.

You can customize this variable.

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  • auto-saving backups the file but it doesn't save the file itself. So my question remains unanswered. Thank you anyway.
    – Name
    Commented Jan 31, 2015 at 3:23
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    How about using save-buffer (or a custom function that essentially uses save-buffer when there is a valid buffer-file-name) in conjunction with the auto-save-hook? -- This normal hook is run whenever an auto-save is about to happen. gnu.org/software/emacs/manual/html_node/elisp/…
    – lawlist
    Commented Jan 31, 2015 at 4:39
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    +1 why not incorporate the comment of @lawlist in the current answer of Dan or write a separate answer.
    – Name
    Commented Jan 31, 2015 at 10:11
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    @lawlist: good idea -- do you want to write that up as an answer?
    – Dan ♦
    Commented Jan 31, 2015 at 11:59
  • @Dan -- the idea was primarily yours -- I just looked into whether it was a standard Emacs concept where modes generally have hooks, or a run-hooks statement at the end of a base function. The answer / credit belongs to you. :) As you know, there are certain modes / functions that place a buffer-file-name on a non-file-visiting-buffer -- I'm not sure how you are going to deal with that situation because save-buffer may prompt/offer the user confirmation to save . . . there are probably other exceptions also where a file hasn't been saved yet. Maybe a valid-file check would be needed.
    – lawlist
    Commented Jan 31, 2015 at 16:15

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