OneTaskBy Tim King · Updated
Cron Cheat Sheet
Crontab Syntax, Five Fields, @ Shortcuts and Thirty Ready-Made Schedule Examples
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How the Cron Cheat Sheet works
This cron cheat sheet covers the whole crontab syntax on one page: the five fields and their ranges, the four operators, the @ shortcuts, and thirty common schedule expressions you can copy straight into a crontab. Search for a schedule in words, or paste an expression into the cron builder linked below to see its next run times.
Reading the cron cheat sheet
A crontab line is five fields followed by the command: minute, hour, day of month, month and day of week. Each field takes a number, a star for every value, a comma-separated list, a range with a hyphen or a step with a slash. */15 9-17 * * 1-5 therefore means every fifteen minutes from 09:00 to 17:45, Monday to Friday.
The day-of-month and day-of-week trap
When both day fields are restricted, standard cron runs the job when either one matches, not both. 0 0 13 * 5 runs on every 13th and on every Friday, not only on Friday the 13th. To get the intersection, restrict one field and test the other in the command, for example with [ "$(date +\%u)" = 5 ].
Time zones and missed runs
Cron uses the server's local time zone unless the crontab sets CRON_TZ or TZ, so jobs can run twice or not at all when clocks change. Schedule daily jobs away from 01:00 to 03:00 if the server observes daylight saving. Plain cron also skips runs while the machine is off; anacron or a systemd timer with Persistent=true catches up instead.
FAQ
How do I run a cron job every 5 minutes?
Use */5 * * * *. The step in the minute field matches 0, 5, 10 and so on up to 55, in every hour of every day. For every five minutes during working hours only, restrict the hour and weekday fields as well, for example */5 9-17 * * 1-5.
Does cron support seconds?
Standard cron does not; the smallest unit is one minute. Quartz, Spring and some cloud schedulers add a seconds field at the front, making six or seven fields, which is why expressions copied between systems sometimes fail. For sub-minute work, use a loop with sleep or a systemd timer.
Can I print or reuse this cron reference?
Yes. Print the page, or download the CSV or JSON and add it to a runbook or a wiki. The table is written by OneTask and released under CC0, so you can copy it anywhere without asking or crediting the source.
See also: all Tech Data tools, Everyday Data.
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