Understanding "at"

Many a time, we need to schedule a task for a future time, say in the evening at 8 p.m. on a specific day. We can use the at command in such a situation.

Sometimes, we need to repeat the same task at a specific time, periodically, every day, or every month. In such situations, we can use the crontab command.

Let's learn more about the use of the at command. To use the at command, the syntax is as follows:

    $ at time date

The following are examples of the at command:

• The Ctrl + D command will save the at job. The task will be executed at 11.15 A.M. This command will log messages to the log.txt file at 11.15 a.m.:

    $ at 11.15 AM
    at >  echo "Hello World" > $HOME/log.txt
    at >  Control + D

• The following command will send an email on March 31, 2015, at 10 A.M.:

    $ at 10am mar 31 2015
    at> echo "taxes due" | mail jon
    at> ^D

• The following command will make the task run on May 20 at 11 A.M.:

    $ at 11 am may 20
  

• All the jobs that are scheduled by the at command can be listed using the following command:

    $ atq 

• To remove a specific job listed by the atq command, we can use the following command:

    $ atrm  job-id