What would be the crontab entry look like for a job that runs on the first day of every third month?
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The following will run script on the 1st of Jan, Apr, Jul and Oct at 03:30
30 03 01 Jan,Apr,Jul,Oct * /path/to/script
Alternatively, but less obvious
30 03 01 */3 * /path/to/script
Will run every three months at 03:30 on the 1st of Jan,Apr,Jul and Oct.
Richard Holloway
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5+1: I always thought the / notation was the MOST obvious...I use it wherever possible. (Words in the scheduling part of the crontab freak me out...I'd do: "0 0 1 3,6,9,12 * /path/to/script.bash" if I couldn't do /3) – Satanicpuppy Apr 06 '10 at 14:27
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9@warren No it would not. The logic here is more of a mod truth statement. Ex: if(12%3 == 0): run_script(). I thought about this as well! Great question. – Goahnary Dec 28 '16 at 19:13
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1@Goahnary I realized that a while after I asked for the clarification, too :) – warren Dec 28 '16 at 19:15
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4@warren it really should be a mod operator rather than a division. But oh well ¯\_(ツ)_/¯ – Goahnary Dec 28 '16 at 19:17
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@Goahnary So I think it will run on Mar, Jun, Sep, & Dec right rather than in answer: 'Jan,Apr,Jul,Oct' – bharat Jun 04 '19 at 05:09
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Wikipedia has a nice explanation about how to configure Cron.
For your specific case you could run a Cron Expression to run every 3 months- obviously change the months to suit your schedule.
0 0 1 JAN,APR,JUL,OCT * /path/to/script.bash
David Spillett
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Jon Rhoades
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The accepted answer is good, thou I'd use an alternative with simpler numbers and easier to read: https://crontab.guru
0 0 1 */3 *
Read like this: “At 00:00 on day-of-month 1 in every 3rd month.”
Josiel Faleiros
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