That's a poorly phrased question, to be honest. In one sense the point in time where the job is scheduled has to be different -- it's a point in time in a different 24 hour period.
But in another sense (a sense closer to what you probably intended) the point in time can't be guaranteed to be different. There's a finite number of minutes in a day and picking one pseudo-randomly would occasionally collide. Consider, as an extreme example, a system which reboots often and is only up for 1 minute every 24 hour period. But, such collisions should be rare, and that specific extreme case example was ludicrous. Anyways, on a normally operating machine, you should expect the same minute to be used slightly more often than once every four years. And, a difference less than 2 minutes would happen more often (around once a year, depending on exactly where you draw the line). But, if you don't trust what I have said here (and maybe you should not) what you really want to understand is the algorithm being used, and the best way to discover that is to look at the implementation. https://www.openbsd.org/anoncvs.html -- Specifically, you'll want to look at the implementation of get_range() in usr.sbin/cron/entry.c FYI, -- Raul On Thu, Apr 16, 2020 at 12:41 PM Andreas Kusalananda Kähäri <[email protected]> wrote: > > Thanks for that! > > Also, considering a job scheduled like > > ~ ~ * * * somecommand > > I'm assuming, provided that the cron daemon is not restarted, this would > run the job at a single random point in each 24h period, right? A > *different* point in time, each 24 period? > > > > On Thu, Apr 16, 2020 at 10:28:34AM -0600, Theo de Raadt wrote: > > Yes. > > > > But that problem already existed with the minutes field being >close to > > the moment cron was restarted. > > > > Only difference is now you don't know the minute. > > > > > > Andreas Kusalananda Kähäri <[email protected]> wrote: > > > > > Thanks for the ~ crontab(5) feature! > > > > > > Question: If the cron daemon is restarted (e.g. via reboot) during the > > > interval during which a cron job may be randomly triggered, is there a > > > risk (or even guarantee) that the job may run a second time? > > > > > > > > > Regards, > > > > > > -- > > > Andreas (Kusalananda) Kähäri > > > SciLifeLab, NBIS, ICM > > > Uppsala University, Sweden > > > > > > . > > > > > -- > Andreas (Kusalananda) Kähäri > SciLifeLab, NBIS, ICM > Uppsala University, Sweden > > . >
