Cron Expression: Every Minute
The expression is * * * * *. Paste it above to confirm the reading. Below: what all-wildcards means and why every-minute jobs need a lock.
The expression
* * * * * runs a job every minute, 24/7 — 1,440 times a day.
Field by field
Every field is a wildcard: any minute, any hour, any day of month, any month, any weekday. There is no more frequent standard cron schedule than this.
Watch out for overlap
If your job can take longer than a minute, two copies will run at once. Wrap it with flock or an application-level lock so only one instance runs.
Common variations
Every minute during business hours: * 9-17 * * 1-5. Every 2 minutes: */2 * * * *.
FAQ
How many times a day does * * * * * run?
1,440 times — once per minute, all day.
Can cron run more often than every minute?
Standard cron cannot; its smallest unit is one minute. For seconds you need a loop, a systemd timer, or a scheduler like Quartz.
How do I stop overlapping runs?
Use flock (e.g. flock -n /tmp/job.lock yourcommand) so a second copy exits if one is still running.