gistfile1.sh

#!/bin/bash

interfaces() {
	ip addr list | egrep '^[0-9]' | awk '{print $2}' | sed -e "s/://g" | grep -v lo | sort -g
}

is_default() {
	local int=$1
	local default_int=$(ip route show | grep default | awk '{print $5}')
	[ "x$int" == "x$default_int" ]
}


cfg_for() {
	local int=$1
	ifconfig $int | grep 'inet addr' | sed -e "s/[^0-9\. ]//g" | while read ip bcast netmask; do
		cat << EOF

auto $int
iface $int inet static
address $ip
broadcast $bcast
netmask $netmask
EOF
	if is_default $int; then
		echo "gateway 74.201.193.1"
		echo "dns-nameservers 172.29.11.26 172.29.11.25"
	fi
	done
}

loopback() {
cat << EOF
auto lo
iface lo inet loopback
EOF
}

routes() {
	route -n | egrep -v '\b0\.0\.0\.0\b' | egrep '^[0-9]' | while read pfx gw netmask _; do 
		echo "post-up route add -net $pfx netmask $netmask gw $gw"
	done
}

loopback

for i in $(interfaces); do
	cfg_for $i
done

routes