Shell Programming and Scripting

hostname -i

dig +short $(hostname -f)

ip addr show <interface> | sed -ne '/inet/s/.* \([0-9]\+\.[0-9]\+\.[0-9]\+\.[0-9]\+\).*/\1/p'

OS=`uname`
IO="" # store IP
case $OS in
   Linux) IP=`ifconfig  | grep 'inet addr:'| grep -v '127.0.0.1' | cut -d: -f2 | awk '{ print $1}'`;;
   FreeBSD|OpenBSD) IP=`ifconfig  | grep -E 'inet.[0-9]' | grep -v '127.0.0.1' | awk '{ print $2}'` ;;
   SunOS) IP=`ifconfig -a | grep inet | grep -v '127.0.0.1' | awk '{ print $2} '` ;;
   *) IP="Unknown";;
esac

echo "$IP"