Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!prcrs!paul
From: paul@prcrs.UUCP (Paul Hite)
Newsgroups: comp.unix.questions
Subject: Re: Cron
Message-ID: <356@prcrs.UUCP>
Date: 6 Dec 89 14:53:05 GMT
References: <14202@orstcs.CS.ORST.EDU>
Organization: PRC Realty Systems, McLean, VA
Lines: 20

In article <14202@orstcs.CS.ORST.EDU>, ghe@nucthy.physics.orst.edu (Guangliang He) writes:
> 
> I thought I understand how cron work until a minute ago. My SYS V
> machine died last night and I booted it up this morning. After I loged
> on, I found the time is still on last night. So I set the date.
> Everything is ok. A while ago, I got a mail from cron report the daily
> backup was completed. This surprised me.  

If cron is running when you change the date it tries to compensate.  If you
set the clock back, cron waits for awhile so that it won't run something 
twice.  And if you set the clock ahead (as I believe that you did), cron
runs continuously until it catches up.

This behavior of cron is useful if you're just tweaking the clock.  But if you
make a major change to the system time you probably should kill cron first,
set the time, and restart cron.  This way cron won't notice a clock change, so
it won't try to compensate.  

Paul Hite   PRC Realty Systems  McLean,Va   uunet!prcrs!paul    (703) 556-2243
                      DOS is a four letter word!