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Module 4: Process Management

Lesson 42: at Command

In this lesson, you'll learn how to use the at command to schedule a command to run once at a given time in Linux.

Lesson 42: at Command
at Command: A job scheduling tool for executing commands at a specified future time

The at command is a Linux/Unix command-line utility utilized for scheduling a command to run once at a given time without editing a configuration file.

It is a useful job scheduler for automating tasks that need to occur at a later point without manual intervention.

Note: It is an alternative to the cron job scheduler.

Install and Enable the at Service

The only requirement consists of installing this utility and starting and enabling its execution:

# yum install at        # CentOS based systems
$ sudo apt-get install at  # Debian and derivatives

Next, start and enable the at service at boot time by executing the following commands:

# On SystemD
# systemctl start atd
# systemctl enable atd

# On SysVinit
# service atd start
# chkconfig --level 35 atd on

at Command Syntax

$ at [OPTIONS] TIME

at Command Options

Option Description
-m Send an email to the user when the job is done (requires Postfix or equivalent)
-l List all pending jobs (same as atq)
-d JOB_ID Delete a pending job (same as atrm)
-f FILE Read commands from a file instead of stdin
-v Show the time the job will be executed
now Schedule the job to run immediately
noon Schedule the job to run at 12:00
midnight Schedule the job to run at 00:00

1. Schedule a Command to Run at a Specific Time