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Crontab auditor
Paste your whole crontab. Every line is explained, and the classic mistakes are flagged before they cost you a night's sleep.
The traps this tool looks for
- The OR trap. Setting both day-of-month and day-of-week makes cron run when either matches, so
0 0 13 * 5fires every Friday and every 13th. - Short months. A job on the 31st skips April, June, September, November and February.
- Unescaped %. Cron converts it to a newline and your command is cut off.
- Mail floods. A job that prints output and has no redirection emails it every run.
- Thundering herd. Many jobs at 00:00 fight for the same resources. Spread them out.
Frequently asked questions
What does the auditor check?
Syntax, schedules that never fire, the day-of-month/day-of-week OR trap, jobs that skip short months, unescaped % characters, missing paths, missing output redirection, jobs that run every minute, and many jobs starting at the same minute.
Why is % a problem in a crontab?
In a crontab command, an unescaped % is turned into a newline, which silently truncates your command. Write \% instead, for example in date +\%F.
Why does cron need full paths?
Cron runs with a minimal environment and a short PATH. A command that works in your shell may not be found. Use absolute paths.
Is my crontab uploaded?
No. It is analysed in your browser.