traffic.sh

#!/bin/bash

#shows traffic on the specified device

function human_readable {
        VALUE=$1
        BIGGIFIERS=( B K M G )
        CURRENT_BIGGIFIER=0
        while [ $VALUE -gt 10000 ] ;do
                VALUE=$(($VALUE/1000))
                CURRENT_BIGGIFIER=$((CURRENT_BIGGIFIER+1))
        done
        #echo "value: $VALUE"
        #echo "biggifier: ${BIGGIFIERS[$CURRENT_BIGGIFIER]}"
        echo "$VALUE${BIGGIFIERS[$CURRENT_BIGGIFIER]}"
}

###CHECKS####

DEVICE=$1
IS_GOOD=0
for GOOD_DEVICE in `grep ":" /proc/net/dev | awk '{print $1}' | sed s/:.*//`; do
        if [ "$DEVICE" = "$GOOD_DEVICE" ]; then
                IS_GOOD=1
                break
        fi
done
if [ $IS_GOOD -eq 0 ]; then
        echo "Device $DEVICE not found. Should be one of these:"
        grep ":" /proc/net/dev | awk '{print $1}' | sed s/:.*//
        exit 1
fi

###REAL STUFF
LINE=`grep $1 /proc/net/dev | sed s/.*://`;
RECEIVED=`echo $LINE | awk '{print $1}'`
TRANSMITTED=`echo $LINE | awk '{print $9}'`
TOTAL=$(($RECEIVED+$TRANSMITTED))

echo "Transmitted: `human_readable $TRANSMITTED`"
echo "Received: `human_readable $RECEIVED`"
echo "Total: `human_readable $TOTAL`"

SLP=3
echo "Sleeping $SLP to calculate speed..."
sleep $SLP

LINE=`grep $1 /proc/net/dev | sed s/.*://`;
RECEIVED=`echo $LINE | awk '{print $1}'`
TRANSMITTED=`echo $LINE | awk '{print $9}'`
SPEED=$((($RECEIVED+$TRANSMITTED-$TOTAL)/$SLP))

echo "Current speed: `human_readable $SPEED`/s"

Added formatting, up/down/total throughput and made it embedded-compatible: https://gist.github.com/dagelf/ab2bad26ce96fa8d79b0834cd8cab549