How I get eth0 ip address

hostname -I|sed -e 's/\s.*//g'

If you have any better idea - write it in comments please. Also, if anybody knew how to get external ip address, write it too.

Updated:
ifconfig eth0|grep 'inet '|sed -e 's/[A-Z,a-z,:]//g;s/^\s*//g;s/\s.*//g'

if you're get fear from regexp:

ifconfig eth0|grep 'inet addr'|sed -e 's/[A-Z,a-z,:]//g'|awk '{print $1}'