#!/bin/sh

if [ "$1" = "" ]; then
	echo "Please provide one of the following interfaces as a parameter: (ie. ./iftop.sh eth0)"
	grep -v lo /proc/net/dev | grep -v Inter | grep -v face | awk '{print $1}' | tr -d ':'
	exit 1
fi

LASTRX=$(grep "$1" /proc/net/dev | awk '{print $2}')
LASTTX=$(grep "$1" /proc/net/dev | awk '{print $10}')
printf "%9s %12s %12s\n" "Interface" "Received" "Transmitted"
echo "------------------------------------"
LINES=0
while :; do
	sleep 1
	LINES=$((LINES+1))
	RX=$(grep "$1" /proc/net/dev | awk '{print $2}')
	TX=$(grep "$1" /proc/net/dev | awk '{print $10}')

	RXDIFF=$(($RX-$LASTRX))
	TXDIFF=$(($TX-$LASTTX))

	LASTRX=$RX
	LASTTX=$TX

	if [ $RXDIFF -gt $((1024*1024*1024)) ]; then
		RXMOD="GB/s"
		RXDIFF=$((RXDIFF/1024/1024/1024))
	elif [ $RXDIFF -gt $((1024*12024)) ]; then
		RXMOD="MB/s"
		RXDIFF=$((RXDIFF/1024/1024))
	elif [ $RXDIFF -gt 1024 ]; then
		RXMOD="KB/s"
		RXDIFF=$((RXDIFF/1024))
	else
		RXMOD="Bytes/s"
	fi

	if [ $TXDIFF -gt $((1024*1024*1024)) ]; then
		TXMOD="GB/s"
		TXDIFF=$((TXDIFF/1024/1024/1024))
	elif [ $TXDIFF -gt $((1024*12024)) ]; then
		TXMOD="MB/s"
		TXDIFF=$((TXDIFF/1024/1024))
	elif [ $TXDIFF -gt 1024 ]; then
		TXMOD="KB/s"
		TXDIFF=$((TXDIFF/1024))
	else
		TXMOD="Bytes/s"
	fi

	if [ $LINES -eq 20 ]; then
		echo
		printf "%9s %12s %12s\n" "int" "Received" "Transmitted"
		echo "------------------------------------"
		LINES=0
	fi

	printf "%9s %4s %7s %4s %7s\n" $1 $RXDIFF $RXMOD $TXDIFF $TXMOD

done