cron behavior

[John Abreau]

jbk <jbk at mail2.gis.net> writes:

> I want my full backup script to run every fourth Monday and
> I thought the following sintax would do that, but this
> morning it ran again, this is the second Monday in the
> cycle.
> 
> '15 4 * * 1/4 /etc/backup/backup monday
> >>/var/log/backup/tape.log'
> 
> Does this syntax only work on the HOUR & DAYS_OF_MONTH
> fields? The man page doesn't say.

Yes, I ran into this same problem 15 years ago when I wanted to
use cron to send out monthly reminders for BCS meetings.
Unfortunately, this is indeed the "correct" behavior for cron; the
day-of-week field is inherently broken by design. I've never really
understood the rationale for it, as this seriously limits cron's 
flexibility.


-- 
John Abreau / Executive Director, Boston Linux & Unix 
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