Crontab Generator Časté dotazy

Cron uses 5 fields: minute (0-59), hour (0-23), day of month (1-31), month (1-12), and day of week (0-6, Sunday=0). For example, '30 14 * * 5' runs at 2:30 PM every Friday. Use * for 'every value', ranges like 1-5, lists like 1,15, or steps like */10.

Common issues: 1) Cron daemon not running (check with 'systemctl status cron'), 2) Wrong user's crontab (use 'crontab -l' to verify), 3) Environment/PATH differences (use absolute paths), 4) Syntax errors in the expression, 5) No output redirection (add '>> /var/log/job.log 2>&1' to see errors). Check system logs with 'journalctl -u cron'.

Use '*/5 * * * *'. The */5 in the minute field means 'every 5 minutes' (runs at :00, :05, :10, :15, etc.). Similarly, */10 runs every 10 minutes, */15 every 15 minutes, and so on.

Yes. For weekdays 9 AM to 5 PM hourly: '0 9-17 * * 1-5'. For every 15 minutes during business hours: '*/15 9-17 * * 1-5'. The hour range 9-17 and weekday range 1-5 (Monday-Friday) restrict execution to business hours.

1) Add output redirection: 'command >> /tmp/debug.log 2>&1', 2) Check the log file for errors, 3) Run the exact command manually to test, 4) Verify the cron daemon is running, 5) Check system logs (journalctl -u cron), 6) Ensure you're using absolute paths for commands and files, 7) Test environment with '* * * * * env > /tmp/cron-env.txt' to see what's available.

When both fields are specified (not *), cron uses OR logic. '0 0 13 * 5' runs 'on the 13th OR on Friday', not 'on Friday the 13th'. If you only want Fridays, use '0 0 * * 5'. If you only want the 13th, use '0 0 13 * *'. To get complex day logic, use a script that checks the date.