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Date:      Wed, 23 Aug 2000 08:55:11 -0700
From:      Fred Condo <fred@condo.chico.ca.us>
To:        freebsd-questions@FreeBSD.ORG
Subject:   Re: crontab
Message-ID:  <20000823085511.B5417@absinthe.condo.chico.ca.us>
In-Reply-To: <XFMail.000823051053.dread@texas.net>; from dread@texas.net on Wed, Aug 23, 2000 at 05:10:53AM -0500
References:  <000001c00c63$c5f77b40$99f438cb@gosvald> <XFMail.000823051053.dread@texas.net>

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On Wed, Aug 23, 2000 at 05:10:53AM -0500, Don Read wrote:
> 
> On 22-Aug-00 George Osvald wrote:
> > Hello everyone!
> > 
> > My ISP where I have my web page, is running freeBSD 4.0. I do not know a lot
> > about it. I know how to use crontab to start a script at certain time how
> > ever how do I use crontab to check on the script that is already running? I
> > have a long running script and restarting it when it is already running
> > doesn't make sense. That only produces a error message.
> > 
> > to start it I would be using something like:
> > 
> > 5     *       *       *       *       root    ./start
> > 
> > This would start the script every five minutes. Now how do I check if the
> > script is running after it's been started and if it wasn't to restart it
> > again. Can anyone help?
> > 
> 
> a directory lock :
> 
> mkdir /tmp/lck.cron > /dev/null 2>&1 || exit

Making this in /tmp exposes the script to a denial of service
attack. If an attacker creates /tmp/lck.cron, then the script will
never run. Best to create your locks under a directory you own.

> 
> echo "got lock, job running"
>  ...
>  your stuff here
>  ...
> 
> rmdir /tmp/lck.cron
> echo "job done"
> 
> 
> 
> Regards,
> -- 
> Don Read                                         dread@texas.net
> --- The problem with people who have no vices is that you can be
>         sure they're going to have some pretty annoying virtues.
> 
> 
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-- 
Fred Condo + fred@condo.chico.ca.us
Not since Tom Hanks won an Oscar has there been that much acting in
Philadelphia. -- Sen. Joe Lieberman, about the Republican Convention.


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