How to schedule to run first Sunday of every month

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I am using Bash on RedHat. I need to schedule a cron job to run at at 9:00 AM on first Sunday of every month. How can I do this?

redhat cron shell bash
11 Answers

It's worth noting that what looks like the most obvious approach to this problem does not work.

You might think that you could just write a crontab entry that specifies the day-of-week as 0 (for Sunday) and the day-of-month as 1-7, like this...

# This does NOT work.
0 9 1-7 * 0 /path/to/your/script

... but, due to an eccentricity of how Cron handles crontab lines with both a day-of-week and day-of-month specified, this won't work, and will in fact run on the 1st, 2nd, 3rd, 4th, 5th, 6th, and 7th of the month (regardless of what day of the week they are) and on every Sunday of the month.

This is why you see the recommendation of using a [ ... ] check with date to set up a rule like this - either specifying the day-of-week in the crontab and using [ and date to check that the day-of-month is <=7 before running the script, as shown in the accepted answer, or specifying the day-of-month range in the crontab and using [ and date to check the day-of-week before running, like this:

# This DOES work.
0 9 1-7 * * [ $(date +\%u) = 7 ] && /path/to/your/script

Some best practices to keep in mind if you'd like to ensure that your crontab line will work regardless of what OS you're using it on:

  • Use =, not ==, for the comparison. It's more portable, since not all shells use an implementation of [ that supports the == operator.
  • Use the %u specifier to date to get the day-of-week as a number, not the %a operator, because %a gives different results depending upon the locale date is being run in.
  • Just use date, not /bin/date or /usr/bin/date, since the date utility has different locations on different systems.
user_17095870

There is a hacky way to do this with a classic (Vixie, Debian) cron:

0 9 1-7 * */7

The day-of-week field starts with a star (*), and so cron considers it "unrestricted" and uses the AND logic between the day-of-month and the day-of-week fields.

*/7 means "every 7 days starting from weekday 0 (Sunday)". Effectively, this means "every Sunday".

Here's my article with more details: Schedule Cronjob for the First Monday of Every Month, the Funky Way

Note – it's a hack. If you use this expression, make sure to document it to avoid confusion later.

user_58210
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