Today I learned about at, a built-in Unix command that schedules a one-off command to run at a specific time. Unlike cron, which is for recurring tasks, at runs something once and then the job is gone.

# Schedule a command for 10am
echo 'toot post "Hello from the future"'  | at 10:00

# List pending jobs
atq

# See what a job will run
at -c 1

# Cancel a job
atrm 1

On macOS, you need to enable atrun first:

sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.atrun.plist

That’s it. No config files, no services to manage. Just echo "command" | at TIME and walk away. Incredible.