Date: Wed, 18 Jul 2007 05:21:51 +0200 From: Fredrik Tolf <fredrik@dolda2000.com> To: freebsd-questions@freebsd.org Subject: Re: cron job every 5 hours Message-ID: <m3sl7miegg.fsf@pc7.dolda2000.com> References: <000f01c7c56d$da44d640$0200a8c0@satellite> <200707160427.l6G4Rb5q090225@banyan.cs.ait.ac.th> <469AFA30.4050504@u.washington.edu> <200707180233.l6I2XJrw097658@banyan.cs.ait.ac.th>
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Olivier Nicole <on@cs.ait.ac.th> writes: >> Something like: >> >> minute */5 * * * root path/to/scriptname >> >> will do the trick. >> >> Substitute the * in */5 for your desired start time (* being 0). >> >> -Garrett >> >> PS crond won't do 5 hours and every x number of minutes per job (5 hours >> + x mins from end to start), just a flat amount of time (5 hours apart >> from start to start). If you need that type of 'precision', at will >> solve that like Olivier said if you place it at the end of the command. > > I am afraid not. > > */5 means on every hours that is a multiple of 5, not every five > hours. So it will run every day at hour 0, 5, 10, 15 and 20. Between > hour 20 one day and hour 0 the next day there is only 4 hours, not > the "every 5 hours" requested. > > Just to confirm that I launched a cron job yesterday: > > 23 */5 * * * /home/java/on/crontest > > It ran at 15:23, 20:23 and today at 0:23 and 5:23 and so on: > > Date: Wed, 18 Jul 2007 05:23:00 +0700 (ICT) > From: Olivier Nicole <on@cs.ait.ac.th> > To: on@banyan.cs.ait.ac.th > Subject: test crontab 5 hours > X-Virus-Scanned: on CSIM by amavisd-milter (http://www.amavis.org/) > > This is a test for crontab > [...] > Only way to run a job every 5 hours is with at(1). I wouldn't go as far as saying the *only* way. You could make the cron job run every hour and then have an internal check in it (or using a wrapper script that checks it). Kind of like this, maybe? #!/bin/sh unset nogo if [ -r /tmp/lastrun ]; then now=`date +%H` if [ $((($now + 24 - `cat /tmp/lastrun`) % 24)) -lt 5 ]; then nogo=y fi fi if [ "$nogo" = y ]; then exit 0; fi date +%H >/tmp/lastrun # Do real work here
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