Cron - Any advanced options?

[Brian Fox]

On Thu, Apr 23, 2009 at 5:19 AM, mark <m.roth2006 at rcn.com> wrote:

> Kurian Thayil wrote:
> > Hi All,
> >
> > I am using RHEL 5.2 Server and I have 3 cron jobs enabled and all are
> > relating to RSYNC. Now, all of these scripts are run once in every 7
> minutes
> > all day. The problem occurs when the scripts doesn't finish to execute in
> 7
> > minutes. This will result in starting execution of the same script again
> and
> > this will malfunction the setup.
> >
> > Is there an option in CRON, which always check if CRON has started the
> > process and is already running? Cron should execute the script only if
> the
> > the process isn't running already. Any hints on this?
>
> Not that I know of. Sounds like you'll have to add code to the scripts to
> see
> if it's still running, and sleep if it is; along the lines of
>
>        while [ ( ps -ef | grep myscript -c ) > 1 ]; do
>            sleep 60
>        done
>
> (I'm sure I'd have to fiddle with the test, but I don't have time at the
> moment.)
>
>        mark
>
>
An exit is probably better than sleeping.

I like the lockfile except for the need for a watchdog.  Something about
"write the script correctly and you won't need a watchdog" never seems to
apply in real life.