atd

service must be running:

systemctl enable atd
systemctl start atd

at

read commands from standard input or given file (-f). time can be specified as HHMM or HH:MM and can be followed by a date like YY-MM-DD, today or tomorrow. relative times with now + 10 minutes, hours, days, weeks.

echo "notify-send -u critical 'hi there'" | at 1234

atq

show list of queued jobs.

atrm

remove given job from queue.

batch

executes command when system load average drops below 0.8 or the value specified in the invocation of atd (atd -l).