[2024-feb-29] Sad news: Eric Layton aka Nocturnal Slacker aka vtel57 passed away on Feb 26th, shortly after hospitalization. He was one of our Wiki's most prominent admins. He will be missed.
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| — | es:howtos:software:at [2019/02/28 01:42 (UTC)] – creado slackwarespanol | ||
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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 | ||
| + | arguments. | ||
| + | |||
| + | ===== 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 | ||
| + | /// | ||
| + | completion. | ||
| + | < | ||
| + | user@darkstar$ at 16:00 -m -f / | ||
| + | </ | ||
| + | |||
| + | 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}//, | ||
| + | |||
| + | < | ||
| + | user@darkstar$ at -c 4 | ||
| + | #!/bin/sh | ||
| + | # atrun uid=1000 gid=1000 | ||
| + | # mail user 1 | ||
| + | umask 22 | ||
| + | ....Environment Details.... | ||
| + | cd /home/user || { | ||
| + | echo ' | ||
| + | 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:// | ||
| + | * [[http:// | ||
| + | * [[http:// | ||
| + | |||
| + | |||
| + | ====== Sources ====== | ||
| + | |||
| + | <!-- If you copy information from another source, then specify that source --> | ||
| + | < | ||
| + | slackware-package-management|Linux.com]] --> | ||
| + | |||
| + | <!-- Authors are allowed to give credit to themselves! --> | ||
| + | * Originally written by [[wiki: | ||
| + | |||
| + | <!-- Please do not modify anything below, except adding new tags.--> | ||
| + | <!-- You must also remove the tag-word " | ||
| + | l not show up in the Table of Contents --> | ||
| + | {{tag> | ||
