lock mechanism like in desktop.el (was: accidentally started gnus)

lock mechanism like in desktop.el (was: accidentally started gnus)

[Reiner Steib]

[ From the Gnus list, adding emacs-devel. ]

On Sun, Aug 30 2009, Graham Murray wrote:

> Tim Landscheidt <tim@tim-landscheidt.de> writes:
[ citation added ... ]
>> Dan Christensen <jdc@uwo.ca> wrote:
>>> It's amazing how often this has saved me from having two copies of Gnus
>>> running! 
>>> 
>>> (add-hook 'gnus-before-startup-hook 'jdc-gnus-lock)
>>> 
>>> (defun jdc-gnus-lock ()
>>>   (or (equal 0 (shell-command "lockfile -r0 ~/Gnus/lock"))
>>>       (y-or-n-p "Lockfile exists.  Steal lock? ")
>>>       (progn (kill-buffer "*Group*")
>>> 	     (error "Unable to lock ~/Gnus/lock"))))
>>> 
>>> (add-hook 'gnus-after-exiting-gnus-hook 'jdc-gnus-unlock)
>>> 
>>> (defun jdc-gnus-unlock ()
>>>   (shell-command "rm -f ~/Gnus/lock"))

>> That sounds rather interesting. Any chance this could be in-
>> tegrated into the main source?

desktop.el has a lock mechanism that is independent of external
programs.  I'd prefer such a solution.  Maybe the lock mechanism in
desktop.el could be made more generic (and moved from desktop.el to
simple.el/files.el?)  so that other packages could use it without
duplicating the code (and loading desktop.el).

> Or change it so that instead of failing if gnus is already running it
> automatically runs 'gnus-slave' instead.

Prompting could offer this as well.

Bye, Reiner.
-- 
       ,,,
      (o o)
---ooO-(_)-Ooo---  |  PGP key available  |  http://rsteib.home.pages.de/

Re: lock mechanism like in desktop.el

[Stefan Monnier]

> desktop.el has a lock mechanism that is independent of external
> programs.  I'd prefer such a solution.  Maybe the lock mechanism in
> desktop.el could be made more generic (and moved from desktop.el to
> simple.el/files.el?)  so that other packages could use it without
> duplicating the code (and loading desktop.el).

We already have such functionality (lock-buffer, unlock-buffer,
file-locked-p), or am I missing something?


        Stefan

Re: lock mechanism like in desktop.el

[Juanma Barranquero]

On Sun, Aug 30, 2009 at 21:58, Stefan Monnier<monnier@iro.umontreal.ca> wrote:

> We already have such functionality (lock-buffer, unlock-buffer,
> file-locked-p), or am I missing something?

They are unimplemented (and aliased to `ignore') on Windows.

    Juanma

Re: lock mechanism like in desktop.el

[Stefan Monnier]

>> We already have such functionality (lock-buffer, unlock-buffer,
>> file-locked-p), or am I missing something?
> They are unimplemented (and aliased to `ignore') on Windows.

Then the answer should be to implement it for w32 rather than to devise
a new scheme.


        Stefan

Re: lock mechanism like in desktop.el

[Juanma Barranquero]

On Mon, Aug 31, 2009 at 02:38, Stefan Monnier<monnier@iro.umontreal.ca> wrote:

> Then the answer should be to implement it for w32 rather than to devise
> a new scheme.

FWIW, I agree, though it is non-trivial because of different semantics
(the issue has been discussed a few times, IIRC).

But certainly reusing the desktop.el mechanism seems hackish.

    Juanma