#!/bin/bash  while [ "1" ]  do  eth=$1  RXpre=$(cat /proc/net/dev | grep $eth | tr : " " | awk '{print $2}')  TXpre=$(cat /proc/net/dev | grep $eth | tr : " " | awk '{print $10}')  sleep 1  RXnext=$(cat /proc/net/dev | grep $eth | tr : " " | awk '{print $2}')  TXnext=$(cat /proc/net/dev | grep $eth | tr : " " | awk '{print $10}')  clear  echo  -e  "\t RX `date +%k:%M:%S` TX"  RX=$((${RXnext}-${RXpre}))  TX=$((${TXnext}-${TXpre}))  if [[ $RX -lt 1024 ]];then  RX="${RX}B/s" elif [[ $RX -gt 1048576 ]];then  RX=$(echo $RX | awk '{print $1/1048576 "MB/s"}')  else  RX=$(echo $RX | awk '{print $1/1024 "KB/s"}')  fi  if [[ $TX -lt 1024 ]];then  TX="${TX}B/s" elif [[ $TX -gt 1048576 ]];then  TX=$(echo $TX | awk '{print $1/1048576 "MB/s"}')  else  TX=$(echo $TX | awk '{print $1/1024 "KB/s"}')  fi  echo -e "$eth \t $RX   $TX "  done