Shell Programming and Scripting

Hi,

I'm looking for a way to run a backup in the cron every Friday, except every 4th Friday (as we do monthly backups then).

The monthly backups are not the 4th Friday of each month, but every 4th Friday (i.e. we don't want this backup to run on x Friday, then the Friday 4weeks/28days later).

This backup also runs Monday-Thursday getting called normally from the cron, but currently it is run manually on Fridays due to this. I understand we will need another script with validation, and call the normal backup script, then put that in the cron - but unsure how to do it.

Thanks in advance!
Rab

I think the best will be to implement it in the script to check if the day is not the 4'th friday of the month.

Thanks for the reply, although it may not necessarily be the 4th Friday we do our monthly backups. It's every 4 weeks. A good example of this would be in April 2011. Our monthly backups would be on Friday 1st April, and Friday 29th April.

Cheers,
Rab

Maybe you can use this in a script calling the backup procedure

Code:

OFFSET=0 # put any value between 0 and 3 to fix the date of the monthly backup
if (( ( $(date +%U | sed 's/^[0]*//') + OFFSET ) % 4 )) # spaces just for better readability
then
    # weekly backup
else
    # monthly backup
fi

You can add a test to your script like:

Code:

if [ $(date +%d) -lt 22 -a $(date +%u) -eq 5 ];then echo OK;else exit;fi

Thanks - would it be possible to break it down as to what it does?

Cheers,
Rab

One improvement to speed up

Code:

if [  $(date +%u) -eq 5 -a $(date +%d) -lt 22 ];then echo OK;else exit;fi

Reference : Man Page for date (All Section 1) - The UNIX and Linux Forums