I couldn't get the parse ifconfig script to work for me on an AMI so got this to work measuring received traffic averaged over 10 seconds
date && rxstart=`ifconfig eth0 | grep bytes | awk '{print $2}' | cut -d : -f 2` && sleep 10 && rxend=`ifconfig eth0 | grep bytes | awk '{print $2}' | cut -d : -f 2` && difference=`expr $rxend - $rxstart` && echo "Received `expr $difference / 10` bytes per sec"
Sorry, it's ever so cheap and nasty but it worked!
