Ensure only single application instance.

[Alex]

SOP is to write the actual PID of the running process into the pidfile, then
check to a) that the pidfile exists, and b) that the process referenced in
the pidfile exists.  if the pidfile exists, but the process does not, take
over the pidfile and carry on.

On Fri, Aug 29, 2008 at 9:51 AM, Heston James <heston_james at live.co.uk>wrote:

> Good afternoon all.
>
> I have an application/script which is launched by crontab on a regular
> basis. I need an effective and accurate way to ensure that only one instance
> of the script is running at any one time.
>
> After a short look around the internet I found a couple of examples, such
> as this one (http://code.activestate.com/recipes/474070/), however they
> both seem to be focused on a windows based environment.
>
> Can anyone offer their advice on how best to do this on a linux based
> system?
>
> I have been contemplating the idea of creating a pidfile which is destroyed
> at the end of the script, will this suffice? is it fool proof? My only
> concern with this is that if the script crashes or is stopped halfway
> through processing for whatever reason, I'll be left with a dead pidfile on
> the system and no successive runs will work.
>
> I'm really interested to get your ideas guys, Thanks.
>
> Heston
>
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