Replacing cron with mcron

Dan Nelson dnelson at
Thu Feb 9 19:12:17 PST 2006

In the last episode (Feb 09), Michael P. Soulier said:
> On 09/02/06 Iantcho Vassilev said:
> > Has anyone tried this? I even think of proposing this to the base
> > system - cron is such an old idea..
> What does mcron offer? My main complaints about cron are:
> 1. Difficult to do refined timing, like execute on the first tuesday
> of each month. I tend to use remind for this, by David Skoll.

Something like that rule could be done with a bit of shell script:

0 0 0 0 2   [ $(date +%d) -le 7 ] && real_command

For more compilcated rules you may be able to coax /usr/bin/calendar
into doing the date math.  Or have cron call calendar's date parser
directly given a suitably-formatted crontab line.

> 2. It leaves synchronization up to the app, so it will happily start
> multiple instances of a job that's taking too long.
> To work around #2, I find something like daemontools or runit a nicer
> way to solve the problem.

Lockfile from the promail port works for me.  You could probably use
/usr/bin/lockf also.

	Dan Nelson
	dnelson at

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