Re: crontab fun

[Chuck Swiger <cswiger%mac.com@localhost>]

Patrick Welche wrote:
> On Sat, Jul 05, 2008 at 12:01:55PM -0400, Chuck Swiger wrote:
> > Patrick Welche wrote:
> ...
> > > If the rule were _both_ and I wanted _either_, I could write 2 lines
> > > in crontab. The opposite isn't obvious to me. A use case for _both_
> > > would be "run this backup every Friday unless it's the first of the
> > > month (because the different monthly backup is running)" - and I can't
> > > believe I'm the first one to encounter this ;-)
> ...
> > You might also look up Vixie cron, as that supports an extended syntax 
> > for specifying more complex rules.
>
> It seems that we run Vixie cron 3 + patches. Looking at the version 4.1 shar
> (now known as ISC cron), I see that I'm definitely no the first one to
> encounter this :-)
>
> XFrom: ames!seismo!cbmvax!devon!paul
> XTo: cbmvax!seismo!nike!ptsfa!vixie!paul
> XDate: Mon Jan  5 09:29:57 1987
> ...

My goodness, an email with UUCP bang-paths from 21 years ago!  :-)

Well, if a decent solution hasn't been provided since then, I might as well 
flesh out the details of something which could do the job:

30 1 * * 5      /usr/local/bin/schedule_weekly_backup.sh

...in crontab which runs this:

#! /bin/sh

if [ `date +%d` -lt 5 ]; then
  run_monthly_backup.sh
else
  run_weekly_backup.sh
fi

[ s/5/6 if your "friday backup" happens early Saturday morning... ]

Regards,
--
-Chuck