cron for last day of month

dhar · 11-13-2009, 10:52 PM

Hi,

I searched the forum to find the cron for last day of month and i found the following by colucix:

58 23 * * * [ $(date +%d) -eq $(echo $(cal) | awk '{print $NF}') ] && myJob.sh

When i try this i get the following error message:

Subject: Cron <dhar@shell> [ $(date +

Syntax error: end of file unexpected (expecting ")")

Your help would be greatly appreciated.

Thanks
Dhar

ksorge · 11-14-2009, 12:15 AM

Hi Dhar,

You are close with your date calculation, but why don't you try this:

Code:

58 23 * * * [ `date +%d` -eq `cal | sed '/^$/d' | tail -1 | awk '{print $NF}'` ] && myJob.sh

cal - prints the calendar with a blank line at the end (maybe)
sed '/^$/d' - will get rid of the blank line
tail -1 - print only the last non-blank line
awk '{print %NF}' - get the (N)umber of (F)ields column, or the last column in the line

Thanks,
ksorge

dhar · 11-14-2009, 09:16 AM

hi ksorge,

I tried your code too and i get the following error:

Subject: Cron <dhar@shell> [ `date +

Syntax error: EOF in backquote substitution

by the way shell is -> FreeBSD 7.1-STABLE

Thanks

Dhar

fpmurphy · 11-14-2009, 09:36 AM

I suggest that you move the last day of the month logic out of your cron job and into your shell script. Them run your shell script every day or alternatively on days 28-31. The script then tests the date and does nothing if the date is not actual the last day of the month.

dhar · 11-14-2009, 10:18 AM

Thanks

So i can write the script something like this?

#!/bin/sh
[ $(date +%d) -eq $(echo $(cal) | awk '{print $NF}') ]

Thanks

colucix · 11-14-2009, 11:25 AM

Hi Dhar,

the problem in your crontab entry is that the % sign has a special meaning in crontabs. Look carefully at the crontab manual and you will find the explanation:

Quote:

Percent-signs (%) in the command, unless escaped with backslash (\), will be changed into newline characters, and all data after the first % will be sent to the command as standard input.

hence a correct entry would be:

Code:

58 23 * * * [ $(date +\%d) -eq $(echo $(cal) | awk '{print $NF}') ] && /path/to/myJob.sh

You could take also the suggestion by fpmurphy by simply putting this check at the beginning of your script and execute the rest of the code only if the condition is matched, e.g.

Code:

#!/bin/sh
if [ $(date +%d) -eq $(echo $(cal) | awk '{print $NF}') ]
then
  <-- your code here -->
fi

Also don't forget to put full path of your scripts/commands in crontab entries and into the script itself. Indeed, cron has a very limited environment and the PATH is usually limited to /bin:/usr/bin.

Cheers!

PS - I checked the post you refer to... and I forgot to put the backslash before the % sign, there. After more than one year, I can edit it. Thank you for making me notice this "bug".

dhar · 11-14-2009, 12:08 PM

Thank you all very much. I appreciate your time and help. This forum is the best and very very helpful. Keep it up the great work.

Special thanks to colucix!!

Thanks

Dhar

SaintDanBert · 11-14-2009, 02:45 PM

Quote:

Originally Posted by fpmurphy

I suggest that you move the last day of the month logic out of your cron job and into your shell script. Them run your shell script every day or alternatively on days 28-31. The script then tests the date and does nothing if the date is not actual the last day of the month.

I like this idea very much. I suggest that you write a shell function file to hold all of tests like these ... yes, there will be more.
The function calls with parameters will be much more readable in your cron scripts and you won't need to copy and paste the date-time magic strings.

When I used to do lights-out, unattended system admin work, we had a command line utility that took a date-time expression as a parameter.
I don't remember the command program name, sorry. The program used success exit if the expression was true and failure exit if not-true.
It would handle all sorts of date keywords like "today" or "midnight". In addition, it handled things like "last day of next month" or "fifth sunday in June next year".