Re: automatic dired update

[Andreas Politz <politza@fh-trier.de>]

Paul R wrote:
>>> Does anyone know how to make dired auto-refresh? For example, i have
>>> a dired buffer of dir xyz buried somewhere. Then, i renamed some
>>> files in OS's Desktop. Then, when i switch to dir xyz in emacs,
>>> i wish to see the updated list without me having to type g to
>>> refresh. originally i thought just some hook... something like
>>> (add-hook 'dired-load-hook 'revert-buffer)
>>>
>>> but when actually trying to do it, apparently not that simple.
>>> I thought it must be some function or variable that tells me when
>>> buffer display is switched or updated... can't locate it.
> 
> Drew> Good question. To use a hook to call `dired-revert', you need to
> Drew> find a hook that represents the "change" in interaction state that
> Drew> you make when you "switch" to the dired buffer. I'm not sure what
> Drew> hook that might be.
> 
> That would only work if the dired buffer is not currently displayed when
> the change happen.
> 
> I think a real solution would be to use FS notifications systems. I know
> of inotify ( http://en.wikipedia.org/wiki/Inotify ) for linux but
> I suspect such systems exist for most widely used systems. That would be
> a very good addition to emacs.
> 
> Drew> You could use a timer or, say, `display-time-hook' to do it
> Drew> periodically, but that's a sledge hammer.
> 
> As a temporary solution, a combination of :
>  - refresh display on "buffer gets diplayed" event
> and
>  - refresh diplay every N seconds if buffer is already displayed
> could provide the wanted effect.
> 
> Anybody aware of inotify-and-the-likes integration effort to emacs ?
> 



(defvar dired-file-modification-hash (make-hash-table :test 'equal))

(defun maybe-revert-dired-buffers ()
   (walk-windows
    #'(lambda (win)
        (with-selected-window win
          (when (eq major-mode 'dired-mode)
            (let ((mod (gethash default-directory dired-file-modification-hash)))
              (unless (and mod
                           (equal mod (nth 5 (file-attributes default-directory))))
                (setq mod (nth 5 (file-attributes default-directory)))
                (puthash default-directory mod dired-file-modification-hash)
                (dired-revert))))))
    'no-mini 'all-frames))

(run-with-idle-timer 1 t 'maybe-revert-dired-buffers)

This is polling the filesystem, plus I don't know if it is working
on win32.

-ap