crontab 4th Tuesday of month

[Jorge Fábregas]

On 07/28/2012 07:03 AM, Frank Murphy wrote:
> I thought the last tuesday would be covered by above.
> But it has run everyday since 22nd.

Hi,

There's no way to accomplish this via crontab itself.  You'll need a
little help by means of a script.

This works:

1)  create the following script. Let's call it tuesday-check.sh:

#/bin/sh
[ `date +%m` -ne `date -d "+7 days" +%m` ] && your-actual-command.sh


2) create a crontab entry for the above script so that it runs every
Tuesday (yes I know you want the last Tuesday;  the script will
precisely check that):

15 18 * * 2 /root/bin/tuesday-check.sh


Explanation:

date +%m
...returns the *month number* for today

date -d "+7 days" +%m
...returns the "month number" for this day *one week ahead*


For example, if I were to run this on the last Saturday of the month
(today the 28th):

- the first command would return "7".
- the second command would return "8" because the NEXT Saturday is
already August.

Because both of the returned numbers are different (7 and 8) the command
will run.

HTH,
Jorge