Cron is a daemon that runs periodic scheduled jobs.
Use the crontab command to edit the table of scheduled jobs.
Use at to schedule a job for one execution only at a specific date.
Common pitfalls
If a command works when you type it in a terminal but not from a crontab, here are some common reasons:
- Cron provides a limited environment, e.g., a minimal
$PATH. - Cron uses
/bin/sh, which may not be the shell you normally use. - Cron treats the
%character specially (it is turned into a newline in the command).
