Correct. at was a v7-ism. Trying to put a nicer face on the idea - that is to say, I looked at the "at" command as a user-mode (command) front-end to cron so you didn't have to edit the crontab yourself. The later had been around as a system support idea, since at least 6th edition - maybe 5th.

On Tue, Dec 8, 2020 at 1:51 PM Mary Ann Horton <mah@mhorton.net> wrote:

My V6 manual has cron(VIII) - documentation of /usr/lib/crontab - but no
mention of at.

This is consistent with my recollection - I first saw at in V7.

Mary Ann

On 12/8/20 10:11 AM, ron minnich wrote:
> When I got into Unix in 1976 cron and at were both there.
>
> I got to wondering for no particular reason which came first -- I had
> always assumed cron, but ...?
>
> Anyone know?