Shell Programming and Scripting

I am working on a bash script to backup selected servers and am trying to come up with a simpler solution to this problem:

Each server to be backed up has a config file that is read by the script, in the config file are the following values:
LEVEL0=12 #this is the day of the month on which level zero backups are performed.
INTERVAL=3: #In this case every 3 days before or after the LEVEL0 date an interval backup will be performed.

The LEVEL0 and INTERVAL values will be different for different servers.

I could just write a loop to compute if the current day is a day on which to perform an interval backup but it seems that there must be a simpler way to calculate this.

If anyone can point me in the right direction I would appreciate it very much.

If I am not wrong, you just have to determine if the date is one on which an interval backup is to be taken. You could use something like this:

Code:

#!/usr/bin/ksh
d=$(date +%d)

if [ $(($LEVEL0 - $INTERVAL)) -eq $d -o $(($LEVEL0 + $INTERVAL)) -eq $d ]; then
#### take backup here
fi

This bit will just check that it is a day on which you take the intermediate backup. For a level 0 backup, you can just check if the day of the month is the same as the LEVEL0 value.

If you need an interval backup on every INTERVAL days before and after the full backup date then how about using a modulus from the full day number:

Code:

LEVEL0=12   ;# read these value from ...
INTERVAL=3 ;# ... parameter file

d=$(date +%d)

if [ $LEVEL0 -eq $d ]; then
    print backup is Full on day $d           ;# replace by doing something useful here ...
else
  if [ $(( ($d - $LEVEL0) % $INTERVAL)) -eq 0 ]; then
    print backup is Interval on day $d     ;# ... and here
  fi
fi

cheers

blowtorch Thanks. That solved the problem. I knew that there had to be a more elegant solution than what I was using. Tested the code against about 30 date/interval settings and it works as needed.