Linux network interface throughput speed

n.sh

#!/bin/sh
# Forked from https://gist.github.com/dagelf/ab2bad26ce96fa8d79b0834cd8cab549
# With modifications for including timestamp and reporting in Megabits/s instead of Kilobytes/s
#
#  To run: ./n.sh em1

SLP=60 # display / 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
  CUR_TIME=$(date '+%Y-%m-%d %H:%M:%S')
  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))
  # Calculation in Megabits/s
  printf "$CUR_TIME | In: %12i KB/s | Out: %12i KB/s | Total: %12i KB/s\n" $(($INSPEED/1024)) $(($OUTSPEED/1024)) $(($SPEED/1024)) ;
done;