CRON Expression Generator
Build automation scheduling strings for Linux servers and network appliances.
Generated CRON Expression
How It Works
CRON is a time-based job scheduler commonly used on Unix-like operating systems. A standard CRON expression contains five fields: Minute, Hour, Day of the Month, Month, and Day of the Week.
Each field can contain values, ranges, lists, steps, or the wildcard character *. The generator combines the five fields into the exact scheduling syntax required by the CRON service.
Examples and scheduling limits
Enter the five numeric schedule fields or choose a preset. This tool validates field syntax; it does not translate natural language, install a job, or check whether your command will succeed.
*/15 * * * *: at minutes 0, 15, 30 and 45.0 2 * * 0: Sunday at 02:00.30 8 * * 1-5: weekdays at 08:30.
Check the server timezone and cron implementation before deployment. With day-of-week set to *, a schedule for February 31 will never run. When both day-of-month and day-of-week are restricted, common cron implementations match either day condition, not necessarily both. Seconds, named months/weekdays and Quartz extensions are outside this tool's supported syntax. Append your command separately and test it before scheduling.
Reference: crontab manual.
Automated Configuration Backups
Generate expressions to trigger Python scripts that back up core router and switch configurations to a TFTP server every Sunday at 2:00 AM.
Log Rotation
Schedule automated archival and compression of massive syslog files generated by perimeter firewalls to prevent server storage exhaustion.
Database Syncing
Create intervals for synchronizing distributed physical security and credential databases across regional data centers during off-peak hours.
Frequently Asked Questions
Does CRON respect server timezones?
Yes. The cron daemon executes jobs based on the local system time of the server. Always verify your server's timezone configuration (UTC vs. local time) before setting critical maintenance tasks.
What does the asterisk (*) mean?
An asterisk acts as a wildcard, meaning "every" or "all". For example, an asterisk in the "Month" field means the job will run every single month.
From expression to an actual job
For a weekday report at 08:30, enter minute 30, hour 8, day-of-month *, month * and day-of-week 1-5. The output is 30 8 * * 1-5. Add the full path to your tested report command in your user crontab. System crontab files can require a separate user field; this generator does not include it.
Run the command manually under the same account first. Cron may have a smaller PATH and a different working directory than an interactive shell, so use absolute paths and explicitly configure required environment variables. Capture output in an appropriate log and check the next scheduled run.
Common scheduling surprises
Steps are evaluated within each field: */15 in minutes selects 0, 15, 30 and 45 each hour, not 15 minutes after the last execution. A long-running job may overlap with its next invocation unless the command implements locking. Daylight-saving transitions can skip or repeat local times depending on the cron implementation.
The generator checks field ranges, not command permissions, calendar feasibility or completion. Consult the linked cron manual and the documentation for your server’s implementation when those differences matter.