What does the cron expression */20 * * * * mean?

The cron expression */20 * * * * schedules a job to run every 20 Minutes. The five fields represent: minute, hour, day of month, month, and day of week.

How do I schedule a cron job to run every 20 Minutes?

Add this line to your crontab: */20 * * * * /path/to/command. Open your crontab for editing with crontab -e and paste the expression followed by your command.

How do I monitor a cron job that runs every 20 Minutes?

Add a heartbeat check: */20 * * * * /path/to/script.sh && curl -fsS https://cronsignal.io/ping/YOUR_CHECK_ID. You'll be alerted if the job doesn't run on schedule.

Cron Every 20 Minutes — */20 * * * *

Understanding the Expression

The cron expression */20 * * * * breaks down as follows:

Field	Value	Meaning
Minute	*/20	Every 20 minutes
Hour	*	Every hour
Day of month	*	Every day of the month
Month	*	Every month
Day of week	*	Every day of the week

Example Usage

Basic crontab entry

*/20 * * * * /path/to/your/script.sh

With output logging

*/20 * * * * /path/to/script.sh >> /var/log/script.log 2>&1

With monitoring

*/20 * * * * /path/to/script.sh && curl -fsS https://cronsignal.io/ping/YOUR_CHECK_ID

Common Use Cases for Every 20 Minutes

Real-time monitoring: Check system health and service availability
Queue processing: Process background job queues frequently
Cache warming: Keep caches fresh with regular updates
Metrics collection: Gather application and infrastructure metrics

Platform Equivalents

The same schedule expressed across common platforms and schedulers:

Platform	Syntax
Linux crontab	`/20 * * *`
GitHub Actions	`- cron: '/20 * * *'`
systemd timer	`OnCalendar=*:0/20`
Kubernetes CronJob	`schedule: "/20 * * *"`
AWS EventBridge	`cron(0/20 * * * ? *)`

Timezone Considerations

Every-20-minute jobs fire at fixed minute marks: :00, :20, :40. Timezone-independent. Ensure NTP sync to keep the clock accurate.

Common Mistakes

3 runs per hour: Fires at minutes 0, 20, and 40 — not "20 minutes after the last run".
AWS EventBridge syntax: cron(0/20 * * * ? *) uses 0/N step syntax with 6 fields.
Minute-0 contention: All */N expressions fire at minute 0 simultaneously. Stagger with 2/20, 3/20, etc. if you have multiple jobs.

Cron Every 20 Minutes