"at" command and mail

[Brett Glass]

At 02:35 PM 9/3/2011, Robert Bonomi wrote:
 
>Is 'atrun' actually sending the mails or is 'cron' doing it?  'atrun' is
>invoked by 'cron', from a specification in the system crontab file.

/usr/src/libexec/atrun/atrun.c shows an invocation of sendmail(8) directly
from atrun(8).

>Cron emails *whenever* a cron-scheduled job produces stdout or stderr
>output.

atrun intentionally doesn't produce output unless it encounters an error;
see the same source file.

>You could, in theory, have the crontab line _append_ output to a filename
>based on a timestamp, however, that intermixes output from all users.

One way to avoid problems would be to create a file name from a timestamp
and a pid.

The key thing, though, is to avoid mailing on machines that don't have
mail.

--Brett