Using the "at" Command (with examples)

The at command is a useful tool for executing commands or scripts at a specified time. Whether you want to schedule a script to run at a specific time, display a notification at a certain hour, or even send yourself an email with the results of a command, at provides a flexible solution.

In this article, we will explore several different use cases of the at command and discuss the code examples, motivations, explanations, and example outputs for each case.

Use Case 1: Creating a New Set of Scheduled Commands

To create a new set of scheduled commands using the at command, you can open an at prompt by typing at followed by the desired time. After entering the commands, you can save and exit the prompt by pressing Ctrl + D.

Code Example:

at hh:mm

Motivation:

You may need to schedule a set of commands to be executed at a specific time. This could be useful when you want to automate certain tasks or run a script at a later time.

Explanation:

• hh:mm: The desired time when the commands should be executed. For example, at 23:30 will schedule the commands to run at 11:30 PM.

Example Output:

The commands entered within the at prompt will be executed at the specified time.

Use Case 2: Executing Commands and Emailing the Result

If you want to execute commands and receive the result via email, you can use the -m option with the at command. This will send an email with the output of the executed commands using the local mailing program, such as Sendmail.

Code Example:

at hh:mm -m

Motivation:

You might want to receive the output of a command or script via email for monitoring purposes or to keep track of the execution results.

Explanation:

• hh:mm: The desired time when the commands should be executed, same as in the previous example.
• -m: This option informs at to send an email with the output of the executed commands.

Example Output:

The output of the executed commands will be sent to the email address associated with the user account.

Use Case 3: Executing a Script at a Given Time

If you have a script that you want to schedule for execution at a specific time, you can use the -f option with the at command, followed by the path to the script.

Code Example:

at hh:mm -f path/to/file

Motivation:

You might have a script that needs to be executed at a specific time, and using the at command with the -f option allows you to automate this process.

Explanation:

• hh:mm: The desired time when the script should be executed, same as in the previous examples.
• -f path/to/file: This option specifies the path to the script that needs to be executed.

Example Output:

The script specified by the file path will be executed at the specified time.

Use Case 4: Displaying a System Notification

To display a system notification at a specific time, you can use the echo command to send a notify-send message to at with the desired time.

Code Example:

echo "notify-send 'Wake up!'" | at 11pm Feb 18

Motivation:

You might want to set a reminder or display a notification at a specific time to ensure that you remember an important task or event.

Explanation:

• echo "notify-send 'Wake up!'": This command sends a notify-send message to at with the content “Wake up!” as the notification message.
• 11pm Feb 18: The specific time and date when the notification should be displayed. The format can vary based on your system’s localization settings.

Example Output:

At 11 PM on February 18th, a system notification will be displayed with the message “Wake up!”.

Conclusion

The at command provides a convenient way to schedule commands, execute scripts, send email notifications, and display system notifications at specific times. By utilizing the various options and arguments provided by at, you can automate tasks or remind yourself of important events without manual intervention.

Remember to plan your command sequences carefully and double-check the scheduled times to ensure that your desired tasks are executed at the intended moments. With at, you can increase your productivity and keep track of important events with ease.