Realtime Bandwidth monitor

bandwidth.sh

#!/bin/bash
clear

declare -i rxnow txnow txlast rxlast

while true
do
    chain=`ifconfig $1|grep bytes`
    rxnow=`echo $chain | cut -d ":" -f2 | cut -d " " -f1`
    txnow=`echo $chain | cut -d ":" -f3 | cut -d " " -f1`

    rxdelta=$((rxnow-rxlast))
    txdelta=$((txnow-txlast))

    rxk=$(echo "scale=2; $rxdelta/1024"|bc)
    txk=$(echo "scale=2; $txdelta/1024"|bc)

    rxm=$(echo "scale=2; $rxk/1024"|bc)
    txm=$(echo "scale=2; $txk/1024"|bc)

    echo -e "RX=$rxdelta B/s\t$rxk KB/s\t$rxm MB/s"
    echo -e "TX=$txdelta B/s\t$txk KB/s\t$txm MB/s"
    sleep 1
    txlast=$txnow
    rxlast=$rxnow
    clear
done