netstat.sh

#!/usr/bin/env bash

echo "Refresh interval in seconds: "
read interval

function received () {
    local received=`netstat -s -p tcp | grep 'acks' | grep 'bytes' | awk '{ print $4 }'`
    echo "${received}"
}

function sent () {
    local sent=`netstat -s -p tcp | grep 'data packets' | grep -v 'retransmitted' | awk '{ print $4 }' | sed 's/(//'`
    echo "${sent}"
}

received=0
sent=0

while [ true ]; do
    clear
    
    received=$(( `received` - $received))
    sent=$(( `sent` - $sent))
    
    echo "Received ${received} bytes since last refresh ($(( ${received} / 1024 / 1024 )) megabytes)."
    echo "Sent ${sent} bytes since last refresh ($(( ${sent} / 1024 / 1024 )) megabytes)."
    
    received=$(received)
    sent=$(sent)
    
    echo
    
    for ((i=0; i<$interval; i+=1)); do
        remaining=$(( $interval - $i ));
        
        echo -en "Next refresh in ${remaining} second(s).\015"
        
        sleep 1
    done
done