A quick reference guide for “at” utility in Sun Solaris. “at” utility in unix is similar to the “cron” daemon except for that “at” jobs are run only once while cron jobs are recurring. “at” is primarily used to schedule a job which can be command or a script to run once at a particular time although it can be made to reschedule the job. This could be immediatly or at a later time.
The at utility reads commands from standard input and groups them together as an at job, to be executed at a later time.
List AT jobs
To list all the at jobs scheduled on the Sun Server
sunsolaris# at -l
user = root 1210161000.a Wed May 7 12:50:00 2008
user = root 1210161001.a Wed May 7 12:50:01 2008
user = root 1210198500.a Wed May 7 23:15:00 2008
user = root 1210331460.a Fri May 9 12:11:00 2008
user = root 1210198320.a Wed May 7 23:12:00 2008
To run a command at a particular time
sunsolaris# at -t 200805072312
at> reboot
at> <EOT>
commands will be executed using /sbin/sh
job 1210198320.a at Wed May 7 23:12:00 2008
In the above -t switch defines the time that follows it as the time at which the one or more command that follows at the “at>” prompt to be run. Once, all the commands are entered press “CTRL+D” to make “at” aware of the end of commands.
Run a job now
sunsolaris# at now
at>reboot
at> <EOT>
commands will be executed using /sbin/sh
job 1210100190.a at Tue May 6 19:56:30 2008
Run at noon (12pm)
sunsolaris# at noon
at> uname -a
at> <EOT>
commands will be executed using /sbin/sh
job 1210158000.a at Wed May 7 12:00:00 2008
Run at midnight
sunsolaris# at midnight
at> uname -a
at> <EOT>
commands will be executed using /sbin/sh
job 1210114800.a at Wed May 7 00:00:00 2008
To run a job “n” mins from now
Say you want to run the command in 5 minutes from now
sunsolaris# at now + 5minutes
at> uname -a
at> <EOT>
commands will be executed using /sbin/sh
job 1210100631.a at Tue May 6 20:03:51 2008
To run a script or a file
sunsolaris# at -f /root/myscript now
The above runs the script /root/myscript immediatly. The switch “-f” defines the file to be run instead of commands.
To remove/cancel an at job
sunsolaris# at -r <jobname>
For instance, in the following list of jobs I want to cancel the last job “1210100631.a” job.
sunsolaris# at -l
user = root 1210161000.a Wed May 7 12:50:00 2008
user = root 1210161001.a Wed May 7 12:50:01 2008
user = root 1210198500.a Wed May 7 23:15:00 2008
user = root 1210331460.a Fri May 9 12:11:00 2008
user = root 1210198320.a Wed May 7 23:12:00 2008
user = root 1210158000.a Wed May 7 12:00:00 2008
user = root 1210114800.a Wed May 7 00:00:00 2008
user = root 1210100631.a Tue May 6 20:03:51 2008sunsolaris# at -r 1210100631.a
sunsolaris# at -l
user = root 1210161000.a Wed May 7 12:50:00 2008
user = root 1210161001.a Wed May 7 12:50:01 2008
user = root 1210198500.a Wed May 7 23:15:00 2008
user = root 1210331460.a Fri May 9 12:11:00 2008
user = root 1210198320.a Wed May 7 23:12:00 2008
user = root 1210158000.a Wed May 7 12:00:00 2008
user = root 1210114800.a Wed May 7 00:00:00 2008
Now, you can see the last job removed from the scheduled list.
at job using a desired shell
To use C shell (csh)
sunsolaris -c -f /etc/myfile now
-c specifies the shell to be used as bash.
To use bash (sh)
sunsolaris -s -f /etc/myfile now
-s specifies the shell to be used as bash.
To email user
To email user who scheduled the at job once the at command is run
sunsolaris -m -f /etc/myfile now
The -m specifies at job to email the user once the job is run.
The at jobs are saved as files under
/var/spool/cron/atjobs
To see whats in a job, do a “cat”
sunsolaris# cat 1210114800.a
: at job
: jobname: stdin
: notify by mail: no
: project: 1
export HOME; HOME=’/’
export HZ; HZ=”
export LANG; LANG=’C’
export LOGNAME; LOGNAME=’root’
export MAIL; MAIL=’/var/mail/root’
export PATH; PATH=’/usr/sbin:/usr/bin’
export SHELL; SHELL=’/sbin/sh’
export TERM; TERM=’xterm’
export TZ; TZ=’GB’
$SHELL << ‘…the rest of this file is shell input’
#ident “@(#).proto 1.6 00/05/01 SMI” /* SVr4.0 1.2 */
cd /etc/dhcp
umask 22
ulimit unlimited
uname -a