Path: utzoo!mnetor!uunet!husc6!bloom-beacon!coplex!dean
From: dean@coplex.UUCP (Dean Brooks)
Newsgroups: comp.unix.questions
Subject: Re: Cron
Message-ID: <344@coplex.UUCP>
Date: 19 Jan 88 18:55:00 GMT
References: <11098@brl-adm.ARPA> <449@wa3wbu.UUCP> <1988Jan17.235014.19530@lsuc.uucp>
Reply-To: dean@coplex.UUCP (Dean Brooks)
Organization: Copper Electronics Inc. Louisville, KY
Lines: 28

In article <1988Jan17.235014.19530@lsuc.uucp> dave@lsuc.UUCP (David Sherman) writes:
>In article <449@wa3wbu.UUCP> john@wa3wbu.UUCP (John Gayman) writes:
>>					At different times here,
>>if I make a change in the cron time-table, I do not re-boot the whole
>>machine. I simply kill the current cron job process and start it again
>>from the console. The time/jobs are read in at execution time.
>
>Every cron that I have ever seen or heard of either rereads crontab
>every minute or so (v6 may have done this) or checks its modification
>time and rereads it when it changes.  I would consider a cron that
>has to be killed off and restarted when you change crontab to be
>seriously brain-damaged.  Perhaps you should check whether your
>supposition is really correct.

	Actually, it is truth (perhaps not a desirable one) that cron,
on some machines, checks the crontab entries only on two occasions.
Once when CRON is first executed (or rebooted), and when a user executes
the crontab command.
	From this, cron does NOT need to spawn every minute to check to
see if anything needs to be run; rather, when it DOES execute something,
it checks to see when it needs to wake up again.  It can then remain
dormant until it is needed again.  (As opposed to eating up CPU time
every minute of the day).
	This is true on our machine (PLEXUS P/75 UNIX 5.2(1.7)) and I am
sure quite a few others...

			Hope to be of some help...
		{mit-eddie}!bloom-beacon!coplex!dean