Date: Sun, 14 Jan 2001 16:31:43 -0500 From: Sergey Babkin <babkin@bellatlantic.net> To: John Gregor <johng@vieo.com> Cc: Gerhard.Sittig@gmx.net, leifn@neland.dk, freebsd-hackers@FreeBSD.ORG, gjb@gbch.net Subject: Re: how to test out cron.c changes? (was: cvs commit: src/etc crontab) Message-ID: <3A621ABF.FA2C6432@bellatlantic.net> References: <200101140244.f0E2i3518278@vieo.com>
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John Gregor wrote:
>
> What would happen if the definitions of the hour and minute fields
> were subtly changed to mean "elapsed wall-clock time since local
> midnight"? Then, the DST conversion is no longer ambiguous. "Two
> hours since local midnight" only happens once regardless. On days
> where the clocks change, most scripts would wind up running an hour
> ahead or behind their usual time, but hey, so are many of the people
> :-). There would also have to be an entry in the BUGS section noting
> that some days have 23 or 25 hours, which is accurate.
I believe that the handling of DST change in cron must be fixed.
Practically every commercial Unix (except the very retarded ones)
does that and that's something the sysadmins normally expect.
I'll probably look if I can fix it. The logic I plan to implement
is (this is a quote from somewhere else but it describes my
intentions):
Now the jobs run as intuitively expected. If a job falls
into time interval that disappears during switch from
standard time (ST) to daylight saving time (DST) or is
duplicated during the reverse switch, then it's handled
in one of 2 ways. The jobs that run every hour work
as before, they skip the skipped hour or run in the added
hour as usual. But the jobs that run less frequently
are executed exactly once, they are not skipped nor
executed twice (unless cron is restarted or the user's
crontab is changed during such a time interval).
-SB
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