想要实时查看Linux流量情况，又不想再去下第三方工具，可以直接写脚步运行！

原理：从/proc/net/dev中获取到流量情况，再通过换算并除以间隔时间来得到流量单位M

#------------------
#Author:Administrator
#Created:2015-04-10
#------------------
#!/bin/bash

#使用方法
usage()
{
? echo "useage: $0 ethname intervel"
? exit 0
}

#网口配置
if [ $# -gt 1 ];then
? ethname=$1
? num=`ifconfig|grep ${ethname}|wc -l`
? if [ $num -gt 0 ];then
? ethname=$1
? else
? ? echo "Can't find $ethname,Please Check"
? ? exit 1
? fi
fi

#时间配置
intervel=1
if [ $# -gt 0 ]; then
? interval=$2
? test=`expr "$interval" \* 0`
? if [ "$test" != "0" ]; then
? ? ? ? echo "Invalid param '$interval' . It should be a integer number. Usage: $0 ethname intervel"
? ? ? ? exit -1?
? fi
? if [ $interval -lt 1 ]; then
? ? ? ? echo "Invalid param '$interval' . It should be > 0 (seconds). Usage: $0 ethname intervel"
? ? ? ? exit -1
? fi
fi

#函数判断
if [ $# -ne 2 ]
then
?usage
fi

echo "$0 is starting,Device is $1,Intervel is $2"
echo -e "\n"

typeset Rev old_Rev

eth=$1
intervel=$2

old_Rev=`cat /proc/net/dev|grep $eth| awk '{print $1}'| awk -F : '{print $2}'`
old_Send=`cat /proc/net/dev|grep $eth|awk '{print $9}'`
#echo "old_Rev is $old_Rev"
#echo "Old_send is $old_Send"

while true
?do
?sleep $intervel

?Rev=`cat /proc/net/dev|grep $eth|awk '{print $1}'|awk -F : '{print $2}'`
?Send=`cat /proc/net/dev|grep $eth|awk '{print $9}'`
#echo "Rev is $Rev"
#echo "Send is $Send"

?diff_1=`awk -v Rev=$Rev -v old_Rev=$old_Rev -v intervel=$intervel 'BEGIN{printf "Receive is %6.2f", ( Rev - old_Rev ) / 1024 / 1024 / intervel * 8}'`

?diff_2=`awk -v Send=$Send -v old_Send=$old_Send -v intervel=$intervel 'BEGIN{printf "Send is %6.2f", ( Send - old_Send ) / 1024 / 1024 / intervel * 8}'`

?echo "`date +'%Y-%m-%d %H:%M:%S'` Speed: IN ${diff_1} mbps OUT ${diff_2} mbps"

?old_Rev=$Rev
?old_Send=$Send
done