net_speed of one nic

net_speed.sh

#!/bin/sh

SLP=1 # output / sleep interval
DEVICE=$1
IS_GOOD=0
for GOOD_DEVICE in `grep \: /proc/net/dev | awk -F: '{print $1}'`; do
    if [ "$DEVICE" = $GOOD_DEVICE ]; then
        IS_GOOD=1
        break
    fi
done

if [ $IS_GOOD -eq 0 ]; then
    echo "Device not found. Should be one of these:"
        grep ":" /proc/net/dev | awk -F: '{print $1}' | sed s@\ @@g 
    exit 1
fi

while true; do

LINE=`grep $1 /proc/net/dev | sed s/.*://`;
RECEIVED1=`echo $LINE | awk '{print $1}'`
TRANSMITTED1=`echo $LINE | awk '{print $9}'`
TOTAL=$(($RECEIVED1+$TRANSMITTED1))

sleep $SLP

LINE=`grep $1 /proc/net/dev | sed s/.*://`;
RECEIVED2=`echo $LINE | awk '{print $1}'`
TRANSMITTED2=`echo $LINE | awk '{print $9}'`
SPEED=$((($RECEIVED2+$TRANSMITTED2-$TOTAL)/$SLP))
INSPEED=$((($RECEIVED2-$RECEIVED1)/$SLP))
OUTSPEED=$((($TRANSMITTED2-$TRANSMITTED1)/$SLP))

printf "\033c"
printf "In: %12i KB/s | Out: %12i KB/s | Total: %12i KB/s\n" $(($INSPEED/1024)) $(($OUTSPEED/1024)) $((($INSPEED+$OUTSPEED)/1024)) ;

done;