On Unix-like operating systems, at reads a series of commands from standard input and collects them into one "at-job" which is carried out at a later date.

It differs from cron, which is used for recurring executions (e.g. once an hour, every Tuesday, January 1 every year).

[3] In addition to the graphical user interface for Windows Task Scheduler in Control Panel, Windows provides an at.exe command that schedules commands and programs to run on a computer at a specified time and date (similar to cron).

[2] A sample command to compile a C program at 11:45 a. m. on January 31 would be: or The atq program lists the currently queued jobs, while atrm removes jobs from the queue: In some Unix-like computer operating systems, it uses a daemon, atd, which waits in the background periodically checking the list of jobs to do and executing those at their scheduled time on behalf of at.

The batch command can be used instead of at to only run scheduled jobs if the system's load average is below a certain value.