Plannig cron job

[Igor Sovin]

Hi!
I'm wondering how to plan cron job that runs every forth monday at 4.00 of every month?

[RAC_1 · Accepted solution]

You can not do it directly in cron. you need to use a script that will run on every monday and will execute it further, if it is a 4th monday on the month.

[A. Clay Stephenson]

Cron by itself is not smart enough to do this but coupled with a small utility it can do the job. The trick is to run a script every Monday and then let the script decide if it should execute something or simply exit.

1) Download the attached script, caljd.sh and install it in /usr/local/bin. Set the mode of this file to 755; chmod 755 /usr/local/bin/caljd.sh

2) Create a wrapper script that calls this utility. e.g. /usr/local/bin/mycrontask.sh

---------------------------
#!/usr/bin/sh

PATH=${PATH}:/usr/bin:/usr/local/bin
export PATH
STAT=0
if [[ $(caljd.sh -N) -eq 4 ]]
then
echo "Do your stuff here; it's the 4th Monday"
# remember to set ${STAT} to a non-zero value on failure
fi
# otherwise simply exit
exit ${STAT}
--------------------------------------

3) crontab -l > mycrontab
edit mycrontab and add this line
0 4 * * 1 /usr/local/bin/mycrontask.sh
save the file and
crontab < mycrontab


Here's the caljd.sh attachment. Invoke it as caljd.sh -u for full usage and many examples.

[A. Clay Stephenson]

I assume that by 4:00 you meant 4:00 AM if not change the '4' crontab entry to '16'.

[Muthukumar_5]

You can not directly do with crontab settings.

Work around is,

i) Use crontab setting as:

0 4 * * 1 <script to be executed as /test.sh> 1>/dev/null 2>&1

==> Execute at 4:00 on monday (1). It will execute on all weeks.

ii) To control to execute on month's forth monday then,

<script to be executed as /test.sh>
#!/bin/sh

if [[ $(date +'%d') = $(cal | grep -v '[a-z]' | cut -b 4-5 | grep -Ev ' |^$' | head -4 | tail -1) ]]
then

fi

# END
exit 0

PS:
You got a solution from olympian. This is with system default utility using cal instead of external script.

hth.