#!/bin/bash
extract_file () {
        sed -n '/^ ip address /{s/^ ip address \([^ ]*\) .*/\1/;p;q;}'
}

extract_dns () {
        dig +short "$1" | head -n 1
}

if [ $(extract_file <e.txt) == $(extract_dns "hostname.org") ]; then
        ./vpn2.sh
fi




andrea@andypc:~$ sh -x ee.sh
+ extract_file
+ sed -n /^ ip address /{s/^ ip address \([^ ]*\) .*/\1/;p;q;}
+ extract_dns dfg1.no-ip.org
+ dig +short dfg1.no-ip.org
+ head -n 1
+ [ 79.1.134.136 == 79.1.134.136 ]
[: 1: 79.1.134.136: unexpected operator
andrea@andypc:~$