sh
$ at time date
$ at 11 am may 20
# at 02:00 AM Fri
at> yum update glibc
at> echo "Executing scheduled task" | logger
at> shutdown -r +5 "Server is going to be rebooted in 5 minutes for scheduled task. Please save your work ASAP."
at> <EOT>
job 2 at 2015-02-06 02:00
Ends using CTRL+D that generates the <EOT> bit.
Source: http://www.computerhope.com/unix/uat.htm
Check the processes in the queue
sh
atq
Check content of a job
sh
at -c <job number>
Delete job
sh
atrm <job number>
Also, you can cat/modify the job in /var/spool/cron/atjobs/ or /var/spool/at (in Centos)
If not installed, on Centos, make sure to start also atd service.
sh
# chkconfig atd on && service atd start