Cron Expression: * * * * *
* * * * *
Run every minute
Field Breakdown
| Value | Field | Meaning |
|---|---|---|
| * | minute | every minute |
| * | hour | every hour |
| * | day | every day |
| * | month | every month |
| * | weekday | every weekday |
Running a cron job every minute is rarely necessary and carries real risk. If the job takes more than 60 seconds, a second instance starts before the first finishes. Without flock safety, both run simultaneously — competing for the same resources or processing the same data twice.
Use flock for every-minute jobs
* * * * * flock -n /tmp/myjob.lock /usr/local/bin/myjob.sh
If the job is still running when the next minute fires, the new invocation exits immediately without running.
Related Expressions
*/2 * * * *
Every 2 minutes
*/5 * * * *
Every 5 minutes
*/10 * * * *
Every 10 minutes
*/15 * * * *
Every 15 minutes
*/30 * * * *
Every 30 minutes
Common Use Cases
- Health check polling
- Log tail processing
- Real-time queue drain (use a queue instead)
- Metric collection
Paste your crontab to visualise every job on a 24-hour timeline — detect overlaps, collisions, and get flock-safe versions.
Open Cron Visualiser →Frequently Asked Questions
Is * * * * * the most frequent cron can run?
Yes. Cron's minimum resolution is one minute. For sub-minute scheduling, use a process manager like systemd timers with AccuracySec=1s, or a dedicated job queue like Sidekiq or Celery.
Why does my every-minute job sometimes run twice?
If the job takes over 60 seconds and you don't have flock safety, a second instance starts before the first finishes. Wrap with flock -n /tmp/job.lock to prevent concurrent runs.