Loop Through Variables

Use an array.

#! /bin/bash
servers=( 192.xxx.xxx.2 192.xxx.xxx.3
          192.xxx.xxx.4 192.xxx.xxx.5
          192.xxx.xxx.6 192.xxx.xxx.7
)

for server in "${servers[@]}" ; do
    echo "$server"
done

As the other answers point out, an array is the most convenient way to do this. However, for completeness, the exact thing you are asking for is indirect expansion. Rewritten as follows, your sample will also work using this method:

#!/bin/bash
SERVER1="192.xxx.xxx.2"
SERVER2="192.xxx.xxx.3"
SERVER3="192.xxx.xxx.4"
SERVER4="192.xxx.xxx.5"
SERVER5="192.xxx.xxx.6"
SERVER6="192.xxx.xxx.7"

for ((i=1; i<7; i++))
do
    servervar="SERVER$i"
    echo "${!servervar}"
done

If you're OK with just putting the list of IP addresses in the the for loop, then you might also consider simply using some brace expansions to iterate over whatever you need:

#!/bin/bash

for server in \
192.xxx.xxx.{2..7} \
192.yyy.yyy.{42..50} \
192.zzz.zzz.254
do
    echo "$server"
done

But if you need to reuse the (possibly brace-expanded) list, then using the list to initialize an array would be the way to go:

#!/bin/bash

servers=(
192.xxx.xxx.{2..7} 
192.yyy.yyy.{42..50}
192.zzz.zzz.254 )

for server in "${servers[@]}"
do
    echo "$server"
done

While I would probably go with one of the array answers myself, I’d like to point out that it is possible to loop over names directly. You can do

for name in "${!SERVER*}"; do
    echo "${!name}"
done

or, in 4.3 and up, you can use a nameref:

declare -n name
for name in "${!SERVER*}"; do
    echo "$name"
done

Hat tip ilkkachu for the < 4.3 solution.

Tags:

Bash

Shell Script

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