/krɒn/
noun … “a time-based scheduler that automates recurring tasks on Unix-like systems.”
cron is a Unix daemon that executes scheduled commands or scripts at specified intervals, allowing automation of repetitive system tasks such as backups, log rotation, email notifications, and maintenance routines. Users define scheduled tasks in a configuration file called a crontab, which specifies the timing and command to execute using a concise syntax representing minutes, hours, days, months, and weekdays.
The power of cron lies in its precision and flexibility. Each line in a crontab file includes five time fields followed by the command to run. For example, a task can be scheduled to run every day at midnight, every Monday at 8 a.m., or every five minutes. cron manages execution automatically, logging activity and ensuring tasks run reliably without human intervention.
cron interacts naturally with other Unix utilities. Scheduled commands can invoke Bash or sh scripts, perform file synchronization with rsync, process text with awk or sed, or trigger network operations. This integration allows cron to orchestrate complex workflows across system components efficiently.
In practical applications, cron is used for automated system maintenance, database backups, sending periodic reports, monitoring system health, and scheduling repetitive data processing tasks. Its ubiquity and simplicity make it an essential tool for system administrators and DevOps engineers managing Unix-like environments.
An example of a cron job in a crontab:
# Run backup.sh every day at 2:30 AM
30 2 * * * /home/user/scripts/backup.sh
The intuition anchor is that cron acts like a “mechanical scheduler”: it quietly and reliably triggers tasks at specified times, ensuring repetitive operations run automatically and freeing users from manual intervention.