Cron is a time-based job scheduler in Unix-like computer operating systems. It enables users to schedule jobs (commands or shell scripts) to run periodically at specific times, dates, or intervals. However, the syntax (`* * * * *`) can be notoriously difficult to read and write correctly.
This tool decodes standard 5-field Cron expressions into plain English and calculates the next scheduled execution times based on your current local time. It is an essential utility for DevOps engineers, system administrators, and developers managing automated tasks.
Understanding Syntax
A standard cron expression consists of five fields separated by spaces:
- Minute: 0 - 59
- Hour: 0 - 23 (24-hour format)
- Day of Month: 1 - 31
- Month: 1 - 12 (or JAN-DEC)
- Day of Week: 0 - 6 (Sunday is usually 0 or 7)
Frequently Asked Questions
What does `*/5` mean?
The forward slash `/` indicates a step value. `*/5` in the minute field means "every 5 minutes" (e.g., 0, 5, 10, 15...). In the hour field, it would mean "every 5 hours".
Does this support 6-field cron?
This tool focuses on the standard 5-field Linux/Unix format (Crontab). Some systems like Java (Quartz) or AWS CloudWatch use a 6th field for "Seconds" or "Year," which are not supported by standard system cron daemons.
Why are my cron jobs not running?
Common reasons include:
1. The cron service (daemon) is not running.
2. The script file does not have execute permissions (`chmod +x`).
3. Environment path issues (cron runs with a limited environment, so always use absolute paths like `/usr/bin/php` instead of just `php`).
