at

Execute a task at a specified time

Additional Information

The at command is used to execute commands at a specified time. at allows for a fairly complex set of time specification methods. It can accept time in the hh:mm (hour:minute) format for the current day. If that time has already passed, it will be executed the next day. You can also use vague terms like midnight, noon, or teatime (usually 4 PM) to specify the time. Users can also use 12-hour format, adding AM or PM after the time. Specific dates for command execution can also be specified in formats like month day, mm/dd/yy, or dd.mm.yy. The specified date must follow the specified time.

The above are all absolute timing methods; relative timing can also be used, which is useful for scheduling commands to be executed soon. The format is: now + count time-units, where now is the current time and time-units are units of time such as minutes, hours, days, or weeks. count is the quantity of time. Another timing method is directly using today or tomorrow to specify the completion time for the command.

Syntax

at [-V] [-q queue] [-f file] [-mldbv] time at -c job [job...]

Options

-f: Specify a task file containing specific instructions.
-q: Specify the queue name for the new task.
-l: Display a list of pending tasks.
-d: Delete the specified pending task.
-m: Send an email to the user after the task is completed.

Parameters

Date/Time: Specifies the date and time for task execution.

Examples

Execute /bin/ls at 5 PM three days from now:

[root@localhost ~]# at 5pm+3 days
at> /bin/ls
at> <EOT>
job 7 at 2013-01-08 17:00

Tomorrow at 5:20 PM, output the date to a specified file:

[root@localhost ~]# at 17:20 tomorrow
at> date >/root/2013.log
at> <EOT>
job 8 at 2013-01-06 17:20

After scheduled tasks are set, you can use the atq command to view tasks that have not yet been executed:

[root@localhost ~]# atq
8       2013-01-06 17:20 a root
7       2013-01-08 17:00 a root

Delete a set task:

[root@localhost ~]# atrm 7
[root@localhost ~]# atq
8       2013-01-06 17:20 a root

Display the content of a set task:

[root@localhost ~]# at -c 8
#!/bin/sh
# atrun uid=0 gid=0
# mail     root 0
umask 22
date >/root/2013.log

Execute a task using a task file:

[root@localhost ~]# echo "/bin/ls" > mytask.txt
[root@localhost ~]# at -f mytask.txt 5pm+3 days
job 9 at 2013-01-08 17:00

Execute a task specifying a task queue:

[root@localhost ~]# at -q b 5pm+3 days
at> /bin/ls
at> <EOT>
job 10 at 2013-01-08 17:00

Send an email notification after the task is completed:

[root@localhost ~]# at -m 5pm+3 days
at> /bin/ls
at> <EOT>
job 11 at 2013-01-08 17:00