Re: Removing backup files corresponding to no longer existing files

[Deniz Dogan]

On 2011-05-08 09:39, Rasmus Villemoes wrote:
> Hi,
>
> I use a couple of separate directories to store emacs backup files
> (using backup-directory-alist). But this means that if I decide to
> delete or move some project (which is in its own direcory), just
> deleting or moving the directory leaves all the backup copies
> behind. They will then stay in the backup directories forever.
>
> Is there a way to tell emacs to remove backup files which no longer
> correspond to an actual file?
>
> It's probably not very difficult to write a little (shell/perl) script
> to do this, but I was wondering if there is some builtin way which
> I've overlooked.
>
> Emacs 23.1.1 on Ubuntu 10.10, if it matters.
>
> Thanks in advance,
> Rasmus

I'm a bit late to the party, but I wrote this Emacs Lisp function which 
should do what you want:

(defun delete-old-backups (directory)
  (interactive "DDirectory: ")
  (let ((files (directory-files directory t)))
    (dolist (pair backup-directory-alist)
      (dolist (file files)
        (when (string-match (car pair) file)
          (delete-file (expand-file-name file (cdr pair))))))))

As I don't make use of `backup-directory-alist' myself, I cannot test it 
easily.

You can do this in a slightly different way as well, passing the MATCH 
argument to `directory-files' instead of getting all of the files in 
that directory and checking the regexps afterwards.

Hope that helps!

Deniz