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es:howtos:software:at [2019/02/28 01:42 (UTC)] (actual)
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 +<!-- Reviewed 2013-10-16 mfillpot -->
 +<!-- Add your text below. Start with a Headline (see button bar above). -->
 +====== at - Task Scheduling ======
 +**at** is a task scheduling tool which one-time enables tasks to be
 +performed on your system. The **batch** is
 +like **at** but permforms the one-time tasks when system load permits it, all
 +command and functions of **at** can be replicated by **batch** with the same
 +===== Related Commands =====
 +The following commands are included to monitor the **at** command:
 +  * **at** - The program used to submit a one-time task.
 +  * **atq** - The program used to review the queue of jobs submitted with **at**
 +  * **atrm** - The program used to remove jobs from the at queue.
 +===== at Command Use =====
 +The **at** command can be issued to allow you to write a custom script or
 +point it to a pre-built script. In addition, the broad time specifications
 +allowed increase the complexity.
 +The //-m// argument can be added to any command telling the daemon to mail
 +the user on the local system advising of the completion of the task.
 +==== Scheduling an Existing Script ====
 +This example will tell the **at** application to run the script
 +///​home/​user/​testscript.sh//​ at 4PM today and e-mail the user upon
 +user@darkstar$ at 16:00 -m -f /​home/​user/​testscript.sh
 +As you can see the //-f// argument means **file** as it points to the
 +file that will be executed.
 +==== Scheduling a New Action ====
 +As seen below, when no file is specified the **at** application opens a
 +prompt for the user to enter the new script.
 +user@darkstar$ at 19:40 -m
 +warning: commands will be executed using /bin/sh
 +at> ping -c 4 www.google.com
 +at> echo $?
 +at> <EOT>
 +job 4 at Sun Dec 30 19:40:00 2012
 +The user will need to type the sequence of commands that will be issued
 +within the prompt, upon completion you close the prompt with the
 +The command above instructed **at** to ping google 4 times at 7:40PM, return
 +the application status and e-mail the results to the user.
 +<note important>​
 +Be sure to note the job number, it is the only visible identifier for the job
 +and must be referenced if you wish to remove the job later.
 +==== Reviewing Queued Tasks ====
 +The command **atq** lists the user's pending jobs. The output is Job Number,
 +date, hour, queue and username.
 +user@darkstar$ atq
 +4 Sun Dec 30 19:40:00 2012 a user
 +Once the task number has been noted you can review the commands that are
 +included in the job by issuing the command //at -c {jobnumber}//,​ and example is shown below.
 +user@darkstar$ at -c 4
 +# atrun uid=1000 gid=1000
 +# mail user 1
 +umask 22
 +....Environment Details....
 +cd /home/user || {
 +   echo '​Execution directory inaccessible'​ >&2
 +   exit 1
 +ping -c 4 www.google.com
 +echo $?
 +==== Removing Queued Tasks ====
 +The command **atrm** removes jobs from the pending queue, it does not present
 +any confirmation that the job is removed so it may be advisable to run
 +**atq** after **atrm** to confirm the job has been removed.
 +user@darkstar$ atrm 4
 +====== Further Resources ======
 +  * [[http://​unixhelp.ed.ac.uk/​CGI/​man-cgi?​at|at manual page]]
 +  * [[http://​www.brunolinux.com/​02-The_Terminal/​The_at_Command.html|BrunoLinux]]
 +  * [[http://​sathyaphoenix.wordpress.com/​2009/​01/​18/​using-at-command-to-schedule-jobs-in-linux/​]]
 +====== Sources ======
 +<!-- If you copy information from another source, then specify that source -->
 +<​!-- ​ * Original source: [[http://​www.linux.com/​learn/​tutorials/​261878-intro-to-
 +slackware-package-management|Linux.com]] -->
 +<!-- Authors are allowed to give credit to themselves! -->
 + * Originally written by [[wiki:​user:​mfillpot | mfillpot]]
 +<!-- Please do not modify anything below, except adding new tags.-->
 +<!-- You must also remove the tag-word "​template"​ below. Otherwise your page wil
 +l not show up in the Table of Contents -->
 +{{tag>​howtos task_scheduling author_mfillpot}}

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