mac_changer.sh

#/bin/sh
MD5_TOOL=md5      # on linux set this to 'md5sum'
IFACE=en0         # probably eth0, etc on linux
RANDOM_MAC_ADDRESS=$(dd if=/dev/urandom bs=1024 count=1 2>/dev/null|${MD5_TOOL}|sed 's/^\(..\)\(..\)\(..\)\(..\)\(..\)\(..\).*$/\1:\2:\3:\4:\5:\6/')
sudo ifconfig ${IFACE} ether ${RANDOM_MAC_ADDRESS}
if [[ $? != 0 ]] ; then
    echo "Error changing the MAC address of ${IFACE}"
    exit 1
else
   echo "The interface ${IFACE} has the MAC address: ${RANDOM_MAC_ADDRESS}" 
fi