Cron to run 3rd Tuesday of every odd months

Shell Programming and Scripting
1

Hi,

I need to schedule a script to run on the 3rd tuesday of every odd months at 9 am.
min, hour would be - 0 9
month would be - 1,3,5,7,9,11

Can someone suggest how I can schedule it to 3rd tuesday?

Thanks.

2

Run it on tuesdays and test if the date is 15-21...

1 Like
3

You could also run it each month on 15th to 21st and check if it's a Tuesday.

Here I've done the check in the crontab entry, which is nice if you would like to run the script manually and the day doesn't happen to be a Tuesday:

0 9 15-21 1,3,5,7,9,11 *  [ $(date +'%w') -eq 2 ] && /path/to/your/script

Edit: On some unix versions you may have to specify the full path to date (/usr/bin/date or /bin/date).

2 Likes
4

Thanks vbe and Chubler_XL.

I just changed to run today and tested. I tried two ways:

0 9 22-31 8 2  /path/to/your/script > /path/to/your/log 2>&1

I would think that this cron should run between 22nd and 31st of a month, and since the day of the week = 2, it should run only on Tuesdays. But even if I change that to 3 it ran today.

The second way I tried is :

0 9 22-31 8 * [ $(date +'%w') -eq 2 ] &&  /path/to/your/script

This gives me an error:

Your "cron" job executed on Tue Aug 26 9:00:00 EDT 2014
[ $(date +'

produced the following output:
sh: test: ] missing

Not sure what I am doing wrong.

5

Apologise that percent sign has special meaning in the crontab file (It's use to insert a newline) and will need to be escaped your entry should look like this:

0 9 22-31 8 * [ $(date +'\%w') -eq 2 ] &&  /path/to/your/script

It's no good putting the 2 in the weekday field as the month and weekday are an or condition so it will run every Tuesday AND every month day from 22 to 31

2 Likes
6

Thank you soo much. This is really helpful. I used the above code and it is working as expected.

Is the && used as an AND operator? Cos when I remove it as below, the script does not execute via cron.

0 9 22-31 8 * [ $(date +'\%w') -eq 2 ] /path/to/your/script > /path/to/logfile 2>&1
7

&& is Not an AND operator... Its meaning is: if TRUE( the previous test...) execute what follows, and so it make that line a true one liner. ( the contrary would be || )

1 Like
8

Referring to the bash manpage, && is a "control operator":

       AND and OR lists are sequences of one of more  pipelines  separated  by
       the  &&  and  || control operators, respectively.  AND and OR lists are
       executed with left associativity.  An AND list has the form

              command1 && command2

       command2 is executed if, and only if, command1 returns an  exit  status
       of zero.
1 Like
9

Thank you for the great explanation. This has been really helpful.