What Is a Cron Expression Parser?
A cron expression parser interprets the five- or six-field scheduling syntax used by Unix cron daemons and modern task schedulers. It translates cryptic expressions like “0 */2 * * 1-5” into plain English descriptions such as “At minute 0, every 2 hours, Monday through Friday.” This tool helps developers validate and understand cron schedules before deploying them.
How to Use This Cron Expression Parser
- Enter a cron expression in the standard five-field format (minute, hour, day-of-month, month, day-of-week).
- Read the generated human-readable description of the schedule.
- Review the list of upcoming execution times to verify the expression behaves as expected.
Key Concepts
A standard cron expression has five fields separated by spaces: minute (0–59), hour (0–23), day of month (1–31), month (1–12), and day of week (0–7, where both 0 and 7 represent Sunday). Special characters include * (any value), / (step), - (range), and , (list). Some systems add a sixth field for seconds or year.
Frequently Asked Questions
What does the asterisk (*) mean in a cron expression?
The asterisk is a wildcard that matches every possible value for that field. For example, * in the hour field means the job runs every hour, and * in the day-of-month field means it runs every day.
How do I schedule a job every 15 minutes?
Use “*/15 * * * *”. The */15 in the minute field means every 15 minutes starting from minute 0, so the job runs at :00, :15, :30, and :45 past each hour.
What is the difference between day-of-month and day-of-week?
Day-of-month (field 3) specifies calendar dates (1–31), while day-of-week (field 5) specifies weekdays (0=Sunday through 6=Saturday). If both are set to non-wildcard values, the job typically runs when either condition is met.