The at command in Linux is used to schedule one-time or recurring tasks to be executed at a specified time. It allows users to run commands or scripts at a later time without the need for them to be actively logged in or the terminal to be open.
The basic syntax of the at command is as follows:
at <time> [options]Here’s a table explaining the main parameters and options of the at command:
| Parameter | Description |
|---|---|
| time | Specifies the time at which the command should be executed. The time can be specified in various formats. |
| -f | Reads the command to be executed from the specified file instead of reading from standard input. |
| -m | Sends an email to the user after the command is executed. |
| -q | Specifies the scheduling queue for the job (by default, it uses a queue for immediate execution). |
| -l | Lists the user’s pending jobs. |
| -d | Deletes the specified job from the queue. |
| -V | Display version information and exit. |
| -h | Display help and exit. |
Now, let’s see some examples of how to use the at command:
- Schedule a command to be executed at a specific time:
at 2:30 PM
at> echo "Hello, this is a scheduled task" > ~/task_output.txt
at> <EOT>This example will execute the echo command and write “Hello, this is a scheduled task” to the task_output.txt file at 2:30 PM.
- Schedule a command to be executed at a specific date and time:
at 8:00 AM tomorrow
at> /path/to/my_script.sh
at> <EOT>This example will execute the my_script.sh script at 8:00 AM tomorrow.
- Schedule a command to be executed and send an email notification:
at 10:00 PM
at> echo "Backup completed" | mail -s "Backup Status" user@example.com
at> <EOT>This example will execute the echo command and send an email with the message “Backup completed” to user@example.com at 10:00 PM.
- List the user’s pending jobs:
at -lThis command will list all the pending at jobs scheduled by the current user.
- Delete a pending job:
at -d 1This command will delete the at job with ID 1 from the queue.
The at command is a useful tool for scheduling one-time or recurring tasks in Linux, making it convenient for automation and task management.
