One Time Task Scheduling using "at" Command in Linux

At command can be useful for shutdown system at specified time, Taking one time backup, sending email as reminder at specified time etc. This article will help you to understand the working of at command with useful examples.

Commands used with at:

at : execute commands at specified time.

atq : lists the pending jobs of users.

atrm : delete jobs by their job number.

  1. Schedule first job using at command

    Below example will schedule "ls -l" command to be executed on next 9:00 AM once.

    # at 9:00 AM
    at> ls -l
    at> ^d
    job 3 at 2013-03-23 09:00
    

    Use ^d to exit from at prompt.

  2. List the scheduled jobs using atq

    When we list jobs by root account using atq, it shows all users jobs in result. But if we execute it from non root account, it will show only that users jobs.

    # atq
    3       2013-03-23 09:00 a root
    5       2013-03-23 10:00 a rahul
    1       2013-03-23 12:00 a root
    

    Fileds description:

    First filed: job id Second filed: Job execution date third filed: Job exectuion time Last fileld: User name, under which job is scheduled.

  3. Remove scheduled job using atrm

    You can remove any at job using atrm using there job id.

    # atrm 3
    # atq
    5       2013-03-23 10:00 a rahul
    1       2013-03-23 12:00 a root
    
  4. Check the content of scheduled at job

    atq command only shows the list of jobs but if you want to check what script/commands are scheduled with that task, below example will helps you.

    # at -c 5
    

    In above example 5 is the job id.

    Examples of at Command:

    Example 1: Schedule task at comming 10:00 AM.

    # at 10:00 AM
    

    Example 2: Schedule task at 10:00 AM on comming Sunday.

    # at 10:00 AM Sun
    

    Example 3: Schedule task at 10:00 AM on comming 25′th July.

    # at 10:00 AM July 25
    

    Example 4: Schedule task at 10:00 AM on comming 22′nd June 2015.

    # at 10:00 AM 6/22/2015
    # at 10:00 AM 6.22.2015
    

    Example 5: Schedule task at 10:00 AM on same date at next month.

    # at 10:00 AM next month
    

    Example 6: Schedule task at 10:00 AM tomorrow.

    # at 10:00 AM tomorrow
    

    Example 7: Schedule task at 10:00 AM tomorrow.

    # at 10:00 AM tomorrow
    

    Example 8: Schedule task to execute just after 1 hour.

    # at now + 1 hour
    

    Example 9: Schedule task to execute just after 30 minutes.

    # at now + 30 minutes
    

    Example 10: Schedule task to execute just after 1 and 2 weeks.

    # at now + 1 week
    # at now + 2 weeks
    

    Example 11: Schedule task to execute just after 1 and 2 years.

    # at now + 1 year
    # at now + 2 years
    

    Example 12: Schedule task to execute at mid night.

    # at midnight
    

    Above job will execute on next 12:00 AM

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