Apply hostname from DNS

apply_hostname

#!/bin/sh
# Apply hostname from DNS server
# Author : F-Gaudet 2014

# Usage : drop this file into /etc/NetworkManager/dispatcher.d

interface=$1 status=$2
if [ $status = up ]; then
    ip=$(ip addr | grep $interface: -A2 | tail -n1 | awk '{print $2}' | cut -f1 -d'/' )
    string=$(host $ip) > /dev/null
    ret=$?
    if [ $ret = 0 ]; then
        new_hostname=$(echo $string | cut -d ' ' -f 5 | cut -d '.' -f 1) 
        if [ -n "$new_hostname" ]; then
                current_hostname=$(hostname)
                if [ "$new_hostname" != "$current_hostname" ]; then
                     echo $new_hostname > /etc/hostname
                     hostname $new_hostname
                     domain=$(dnsdomainname)
                     if [ -n "$domain" ]; then
                        sed -i "s/^127.0.1.1.*/127.0.1.1       $new_hostname $new_hostname.$domain/" /etc/hosts
                     else
                        sed -i "s/^127.0.1.1.*/127.0.1.1       $new_hostname/" /etc/hosts
                     fi
                fi
        fi
    else
    echo "Host not found"
    fi
fi