Every minute
The finest-grained cron schedule there is: fires every single minute, all day — built for short debugging runs, not for shipping to production.
Last updated
In plain English
- Fires every minute of every hour
- 1,440 runs per day
Why it’s written this way
All five fields are left as *, so cron imposes no restriction anywhere: any minute, any hour, any day, any month, any weekday. That's the entire expression — the widest-open schedule the format can produce.
Minute is the finest resolution cron understands; there's no field below it. If a job needs sub-minute timing, the job itself has to loop internally — cron just launches it once per qualifying minute.
Edge cases to know
- →That's 1,440 runs a day — useful for confirming a job's plumbing works, but treat it as a placeholder: widen the schedule (say, */5 or hourly) before this ships anywhere real.
- →Each firing starts a brand-new process. A job that takes longer than a minute to finish will have its next invocation start before the previous one is done, unless something serializes them.
- →A minute-by-minute job floods cron's mail or log output fast if MAILTO or logging is on — mute the output deliberately rather than discovering it via a pager alert.
Part by part
- * * * * *
- Every field unrestricted: minute, hour, day-of-month, month, day-of-week. This is the most frequent schedule cron can express — 1,440 runs a day.
Common mistakes
* * * * * /usr/bin/myjobNo output redirection, so cron mails every minute's output to the local user. On a machine where nobody reads local mail, that quietly fills the spool until the disk does.
* * * * * /usr/bin/myjob >> /var/log/myjob.log 2>&1* * * * * php artisan schedule:runA relative command name depends on PATH, and cron's PATH is minimal — typically just /usr/bin and /bin. The job works when you test it by hand and does nothing on schedule.
*/1 * * * *A step of one is identical to a bare asterisk, so it adds a construct without changing behaviour. It reads as though a deliberate interval was chosen when none was.
Questions
Can cron run more often than once a minute?
No — one minute is its floor, and no syntax extends it. The usual workaround is a job that loops with sleep inside the minute, which is fragile; a long-running worker or a systemd timer with an accuracy setting is the better answer.
Is cron the right tool at this frequency?
Often not. A schedule this tight usually means you want a persistent worker consuming a queue, which starts once, holds its connections, and reacts immediately rather than polling sixty times an hour.
How do I stop runs piling up on each other?
Wrap the command in flock with a lock file, so a slow run blocks the next rather than running alongside it. At this frequency it is not optional — any job occasionally taking over a minute will eventually have several copies competing.
Where does all the output go?
To the user's local mail unless redirected, which at 1,440 messages a day is a real problem. Redirect to a log file with rotation configured, or to a logging service, before enabling a schedule this frequent.