What does * mean in a cron expression?

An asterisk (*) means 'every' for that field. '* * * * *' means every minute of every hour of every day. '0 * * * *' means at minute 0 of every hour (i.e., every hour on the hour).

What is a Cron Expression?

Q: What is a cron expression?

A cron expression is a string of five fields (minute, hour, day of month, month, day of week) that defines when a task should run automatically. For example, '0 9 * * 1' runs a task every Monday at 9:00 AM.

Q: What is the difference between cron and crontab?

Cron is the daemon (background service) that executes scheduled tasks. Crontab (cron table) is the file or command used to define the schedule for a user's cron jobs. You edit crontab with 'crontab -e'.

A cron expression is a string of five fields that defines a schedule for automated tasks in Unix-based systems. The expression 0 9 * * 1 means "every Monday at 9:00 AM".

Field Order

┌─────────── minute (0–59)
│ ┌───────── hour (0–23)
│ │ ┌─────── day of month (1–31)
│ │ │ ┌───── month (1–12)
│ │ │ │ ┌─── day of week (0–7, 0 and 7 = Sunday)
│ │ │ │ │
* * * * *

Special Characters

* — every value (wildcard)
, — list of values: 1,3,5
- — range: 1-5 (Monday through Friday)
/ — step: */15 (every 15 units)

Common Patterns

* * * * * — every minute
0 * * * * — every hour, on the hour
0 0 * * * — every day at midnight
0 9 * * 1-5 — weekdays at 9:00 AM
0 0 1 * * — first day of every month at midnight
*/5 * * * * — every 5 minutes
0 0 * * 0 — every Sunday at midnight

Build and validate cron expressions visually: Open Cron Expression Generator →

Frequently Asked Questions

What does */5 mean in a cron expression?

The / character means "every N". In the minute field, */5 means every 5 minutes (0, 5, 10, 15, 20…).

What is the difference between cron and crontab?

Cron is the background daemon that runs scheduled tasks. Crontab is the file where those tasks are defined. Edit it with crontab -e in a terminal.