#! /bin/bash

# Find path to programmes that will be used.
WGET=$(which wget 2> /dev/null)
ECHO=$(which echo 2> /dev/null)
NSUPDATE=$(which nsupdate 2> /dev/null)
HOSTNAME=$(which hostname 2> /dev/null)
IFCONFIG=$(which ifconfig 2> /dev/null)
SED=$(which sed 2> /dev/null)
GREP=$(which grep 2> /dev/null)
CUT=$(which cut 2> /dev/null)
HEAD=$(which head 2> /dev/null)

# If run from cron then the default path does not include /sbin
if [ -z $IFCONFIG ]; then
   IFCONFIG="/sbin/ifconfig"
fi

# Set default zone.
ZONE="bws.local"

# Get host information
host=$($HOSTNAME)
ip=$($HOSTNAME -i)
server="$($GREP nameserver /etc/resolv.conf | $CUT -f 2 -d ' ' | $HEAD -1)"

# Create nsupdate input file.
$ECHO "server $server" > /tmp/nsupdate
$ECHO "zone $ZONE." >> /tmp/nsupdate
$ECHO "update delete $host. A" >> /tmp/nsupdate
$ECHO "update add $host. 86400 A $ip" >> /tmp/nsupdate
$ECHO "send" >> /tmp/nsupdate

# Update DNS.
$NSUPDATE -v /tmp/nsupdate 2>&1