A cron job is a scheduled command that the server runs automatically at defined intervals. It is stored in a crontab file where the timing and the command are written in a concise syntax, allowing the system to trigger the task without human interaction.
Also called: scheduled task, cron
Why it matters
It lets a website perform essential routine work such as backups, cache clearing or email sending without manual effort, which keeps the service dependable and saves the client time and money.
How it works
The cron daemon continuously reads the crontab files (for example /etc/crontab or a user’s crontab accessed via crontab -e), parses the five time fields, and when the current time matches a line, it forks a new process to execute the specified command exactly as written, using the environment defined for the job.
The mistake people make
A common error is assuming the cron environment mirrors a normal shell; missing PATH or other variables mean commands that work locally fail when run by cron, leading to silent failures such as missed backups or unsent newsletters.
