Tips Linux Dhclient Dynamic Hostname

#!/bin/sh
   # Filename:     /etc/dhcp/dhclient-exit-hooks.d/hostname
   # Purpose:      Used by dhclient-script to set the hostname of the system
   #               to match the DNS information for the host as provided by
   #               DHCP.
   #
      
   # Do not update hostname for virtual machine IP assignments
   if [ "$interface" != "eth0" ] && [ "$interface" != "eth1" ] && [ "$interface" != "wlan0" ]
   then
           return
   fi
      
   if [ "$reason" != BOUND ] && [ "$reason" != RENEW ] && [ "$reason" != REBIND ] && [ "$reason" != REBOOT ]
   then
      return
   fi
   
   echo dhclient-exit-hooks.d/hostname: Dynamic IP address = $new_ip_address
   hostname=$(a=$(host $new_ip_address) || { false; } && { echo -n $a | cut -d ' ' -f 5 | cut -d "." -f 1; true; }) || unset hostname &&
   echo ${hostname?} > /etc/hostname &&
   hostname $hostname &&
   export HOSTNAME=$hostname &&
   echo dhclient-exit-hooks.d/hostname: Dynamic Hostname = $hostname

curl -s https://wiki.gsi.de/pub/Epics/TipsLinuxDhclientDynamicHostname/_etc_dhcp_dhclient-exit-hooks.d_hostname -o $file && 
   dos2unix $file && 
   chmod a+r $file