Date: Mon, 17 Sep 2001 02:19:17 +0100 From: Ben Smithurst <ben@FreeBSD.org> To: Alfred Perlstein <bright@mu.org> Cc: Tim Allshorn <ta_iy@hotmail.com>, freebsd-hackers@freebsd.org Subject: Re: Cron pickle Message-ID: <20010917021917.W43502@strontium.shef.vinosystems.com> In-Reply-To: <20010916200714.X968@elvis.mu.org> References: <F243F4r4rPKlNonsYKU00010632@hotmail.com> <20010917014932.V43502@strontium.shef.vinosystems.com> <20010916200714.X968@elvis.mu.org>
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Alfred Perlstein wrote:
> * Ben Smithurst <ben@FreeBSD.org> [010916 19:49] wrote:
>> Tim Allshorn wrote:
>>
>>> I know the cron command has to be something like : 59 23 ? ? * , with
>>> maybe some condition on the end.
>>
>> I think you could use something like
>>
>> 59 23 28-31 * * [ `date -v+1M +%d` -eq 1 ] && /path/to/your/program
>>
>> i.e., check that in one minute's time the day of the month is 1, if so,
>> run the program.
>
> I'm not a date(1) wizard, but there's a possible issue here, if
> the system is loaded cron may skip a beat possibly and that
> conditional may be delayed such that it doesn't trigger.
I thought only advancing it 1 minute would make it safe. My reasoning
for not advancing it by 1 day was that if there was enough load to delay
by 61 seconds, then advancing the time from there by one day would lead
to the 2nd. But I think there would have to be about a 24 hour delay
here for this to go wrong, since advancing it by a minute will still
lead it to end up in the 1st for that long... but then I'm not a date
wizard either, maybe someone who is can step in. :-)
Although just using a file like you suggest might stop everyone being
paranoid that it might go wrong.
--
Ben Smithurst / ben@FreeBSD.org FreeBSD: The Power To Serve
http://www.FreeBSD.org/
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