[SOLVED] A question about for loop (increasing two parameters)

yaron.kadem · 12-27-2011, 10:33 AM

Hi All,

I have a question about the for loop in Bash, I would like to produce plenty of lines using for loop where the first field increases by one but only when the second one reaches its limit.

I would like the third octet of the IP address 1.1.1.1 to change to the number 2 but only when the fourth octet reaches the number 5.

for i in {1..5};do echo "ip route add 1.1.1.$i/32 via 192.168.168.1";done

here is an example of what I need my for loop to do:

ip route add 1.1.1.1/32 via 192.168.168.1
ip route add 1.1.1.2/32 via 192.168.168.1
ip route add 1.1.1.3/32 via 192.168.168.1
ip route add 1.1.1.4/32 via 192.168.168.1
ip route add 1.1.1.5/32 via 192.168.168.1
ip route add 1.1.2.1/32 via 192.168.168.1
ip route add 1.1.2.2/32 via 192.168.168.1
ip route add 1.1.2.3/32 via 192.168.168.1
ip route add 1.1.2.4/32 via 192.168.168.1
ip route add 1.1.2.5/32 via 192.168.168.1

Help would be much appreciated.

Yaron

T3RM1NVT0R · 12-27-2011, 10:51 AM

Hi yaron.kadem,

You have to use 2 loops to achieve the required output. It will look like as follows:

Code:

#!/bin/bash
for j in {1..5}
do
     for i in {1..5}
     do 
            echo "ip route add 1.1.$j.$i/32 via 192.168.168.1"
            if [ $i = 5]
            then 
                  continue
            fi
     done
done

[code]

yaron.kadem · 12-27-2011, 11:04 AM

Wow, thanks a lot, it works perfectly.

thanks

T3RM1NVT0R · 12-27-2011, 11:07 AM

You're welcome. Enjoy linux!!!

Please mark this thread as solved.

David the H. · 12-27-2011, 01:42 PM

Or you can use a single brace expansion expression to do the whole thing:

Code:

printf "%s\n" "ip route add 1.1."{1..5}.{1..5}"/32 via 192.168.168.1"

brace expansion

yaron.kadem · 12-28-2011, 02:25 AM

thanks David for another way to do that.

Yaron