Run a perl or shell script cron job on the first Monday or the Nth weekday of the month

by nixCraft on July 5, 2007 · 12 comments· Last updated July 5, 2007

This is a classic problem. One of our FAQ is about cron job. I received lots of email with a question:

How do I run my script on 3rd Monday or 4th Friday only?

Cron does not offer this kind of facility i.e. you cannot run a script on the Nth weekday of the month.

However with one shell liner you can force to run a script on a given day:

Consider following date command, it will print day:
$ date +%a
Output:

Thu

You can compare output with weekday name using bash test [exrp ] syntax and the control operators && (AND list), you can write:
$ [ $(date '+%a') == 'Thu' ] && echo 'Today is Thu, run a command' || echo 'Noop'

First echo command get exectued only on Thursday. Now all you have to do is write a cron job to execute on first Monday:
# crontab -e
Now append code as follows:
# Run a script called myscript.sh on First Monday at 11:30: 30 11 1-7 * Mon [ "$(date '+%a')" == "Mon" ] && /path/to/myscript.sh

Hope this small tip will save your day. Please do share some of your favorite bash / shell scripting hacks in the comments. I will highlight some of the best in next shell scripting post.

2 Ram March 3, 2011 at 7:32 pm: Hi, I wanted to run a script first Thursday of the every month. I added the script in crontab as per your suggesition. It seems somehow it didn’t work.
syntax:
32 13 1-7 * * ["$(date '+%a')" == "Thu"]&&/warehouse/db2scripts/db2_test.ksh > /tmp/db2_test.del
Can you please let me know if i did anything wrong.
Regards,
Ram.
Reply

3 SREEKUMAR September 17, 2007 at 2:04 am

Hi,
I need to execute a script file with the crontab.
I just enter the entry in cronfile and it is not working…
But I can exectute the script manually from the same location with out any issues…

Please advice on this
# Minute Hour Day of Month Month of Year Day of Week Command
57 * * * * sudo /var/opt/R_5.0.0/WebNMS/mysql/bin/mysqlbackup.sh

4 parashar October 1, 2007 at 7:31 am

what i do to run my script automatically on last day of every month?

5 Nilay December 6, 2007 at 6:03 am

Just to share few lines regarding the problem I faced while setting up shell script thru cron …
Make sure you set at the very top of your script the directory path where you script lies, or else your script will crash using the relative path …
use …
cd `dirname $0`
This will take cron to your scripts directory and execute it form there ..hope it will save some1s time.

6 thegetpr March 12, 2008 at 1:03 pm

how to add php script to cron job

7 Alan March 22, 2008 at 2:00 am

In answer to thegetpr’s question, try this to run a PHP script from cron

50 23 * * * lynx -dump http://www.example.com/scrip.php

8 radar August 2, 2008 at 5:31 am

Whoever put comment #4 it saved me a lot of time, I had a problem running the script in cron, but it did it!

Thanks a lot for your help.

9 James September 10, 2008 at 10:27 pm

I should have read the responses. Post 1 is right. I set this up and discovered the same thing.

Thanks for the tip anyway though it certainly helped me.

10 Eric February 10, 2010 at 6:27 pm

What is the syntax to run it every other Monday?

11 Sandeep Sonawane February 11, 2010 at 5:19 am

Hi ,
I don’t understanding why my perl script is not executing through crontab .
but it runs properly if we run it at command prompt by typing “perl $path_of_script”.
I found that cron daemon reads the line “perl $path_of_script” as command at proper timing defined in crontab and logs it in /var/log/cron.
But it is not executing.
I think it may be issue of environmental variables for cron daemon.
How to debug this issue ?
Thanks for help in advance.

12 brian June 7, 2010 at 11:41 pm

Note that you must escape (\) the % in a crontab entry, otherwise cron will treat the % as a newline and feed the rest of the command line as STDIN. The correct command would be:
30 11 1-7 * * [ "$(date '+\%a')" == "Mon" ] && /path/to/myscript.sh

Thanks for the great tip