Schedule a One-Time Task with the at Command

What at does

The at command reads commands and runs them once at the time you set. If you need a task to repeat, use cron instead.

Install at

at is not installed on every system.

Debian and Ubuntu

sudo apt install at

Red Hat, CentOS and AlmaLinux

sudo yum install at

Make sure the service runs:

sudo systemctl enable --now atd

Syntax

at [option] time

Common options:

Option	Meaning
`-q queue`	Use a job queue (the default is `a`)
`-f file`	Read the job from a file
`-m`	Send an email when the job is done
`-l`	List pending jobs
`-d`	Delete a pending job
`-v`	Show the time the job will run

Common time words: now, noon (12:00), midnight (00:00), teatime (16:00), today, tomorrow, AM, PM. You can also give a full date like 202612311800.

For the full manual, run man at.

Examples

Run a command in 3 minutes

echo "sudo reboot" | at now + 3 minutes

List the waiting jobs

at -l

You can also use atq. The list shows the job number.

Delete a job

at -d 15

List the jobs again to confirm it is gone.

Send an email when the job runs

cat sampleFile.txt | at -m midnight

Show what a job will run

at -c 16

Run on the next Tuesday

at Tuesday +25 minutes

Save the output to a file

echo "df -h > /home/user/storageDetails.txt" | at now + 15 minutes

Quick recap

at runs a task once. cron repeats a task.
Use at -l to list jobs and at -d to remove one.
Add -m if you want an email when the job ends.