Script Variables

[Ruler2112]

I have a question for the people who know what they're talking about.

I'm writing a script. In it, I have a variable named ALLOWIP followed by a number. What I want to do is control the script based on if the variable has something in it or not and run a command (iptables if you must know) for every variable that isn't empty. The only problem is that I don't know how to evaluate a variable in a loop like this. I've done some testing and have so far:

for counter in 1 2 3
do
echo "$ALLOWIP$counter"
done


I'm planning on restructuring the loop as a while once it's done, but the concept is the same. I need to be able to concatenate a string with the contents of a variable, then use the result as the variable name and obtain the contents of that. Anybody know how to do such a thing?

[SpookyEddy]

What shell are you using to interpret the script? Would I be correct in assuming bash?

String concat example..

foo="foo"
echo "bar"$foo

Will append the contents of the variable foo to the string bar, resulting in the output "barfoo".

Instead of echoing that you could assign it to another variable....

foo="foo"
bar="bar"$foo
echo $bar

I am not entirely sure what you are attempting to achieve, so some more details would be a great help.

Regards

ed

[Ruler2112]

What I'm trying to do is have a section at the top of the script identifying what IPs should be allowed to connect to the machine. I have this like so:

ALLOWIP1="192.168.100.1"
ALLOWIP2="192.168.100.2"
ALLOWIP3="192.168.100.3"
ALLOWIP4="192.168.100.4"
ALLOWIPn="192.168.100.n"


What I want to be able to do is, within a loop so I don't have to cut & paste a plethora of if statements and iptables commands, access the value in ALLOWIP1 through n. I know the base name of the variable - $ALLOWIP - and the number - $counter - but don't know how to concatenate the $counter variable onto the string $ALLOWIP and access the value in the variable by that name.

[SpookyEddy]

Would simply iterating over a list work for you? Something like this..

#!/bin/bash

list=("ip_one ip_two ip_three")

for i in $list
do
echo $i
done

Regards

ed

[Ruler2112]

That works perfectly- thanks dude. I've never seen that structure in a script before, but it does exactly what I need.

[SpookyEddy]

Your welcome, glad it worked.