今天碰到一个问题：如何用Shell实现实时监控网卡流量？

不清楚，于是搜索：{http://cn.bing.com/search?q=linux+real+time+network+speed+shell}

# 1.通过ifconfig命令

#!/bin/bash
while : ; do
      time=`date +%Y"-"%m"-"%d" "%k":"%M`
      nic=`ifconfig |grep eth|awk '{print $1}'`
      rx_before=`ifconfig $nic|sed -n "8"p|awk '{print $2}'|cut -c7-`
      tx_before=`ifconfig $nic|sed -n "8"p|awk '{print $6}'|cut -c7-`
      sleep 2
      rx_after=`ifconfig $nic|sed -n "8"p|awk '{print $2}'|cut -c7-`
      tx_after=`ifconfig $nic|sed -n "8"p|awk '{print $6}'|cut -c7-`
      rx_result=$[(rx_after-rx_before)/256]
      tx_result=$[(tx_after-tx_before)/256]
      echo "$time In_Speed: "$rx_result"kbps Out_Speed: "$tx_result"kbps"
      sleep 2
done

# 2.通过读取”/proc/net/dev”文件

awk 'BEGIN{
OFMT="%.3f";
devf="/proc/net/dev";
while(("cat "devf) | getline)
{
    if($0 ~ /:/ && ($10+0) > 0)
    {
        split($1,tarr,":");
        net[tarr[1]]=$10+tarr[2];
        print tarr[1],$10+tarr[2];
    }
}
close(devf);
while((system("sleep 1 ")) >=0)
{
    system("clear");
    while( getline < devf )
    {
        if($0 ~ /:/ && ($10+0) > 0)
            {
                split($1,tarr,":");
                if(tarr[1] in net)
                {
                    print tarr[1],":",($10+tarr[2]-net[tarr[1]])*8/1024,"kb/s";
                    net[tarr[1]]=$10+tarr[2];
                }
            }
    }
    close(devf);
}
}'

# 3.通过读取”/sys/class/net/eth0/statistics/rx_bytes”等文件内容{在/sys/class/net/eth0/statistics/目录下还有更多的统计信息}

#!/bin/bash
if [ -z "$1" ]; then
        echo
        echo Usage:	./$0 network-interface
        echo
        echo Example:	./$0 eth0
        echo
        exit
fi
IF=$1
while true
do
        R1=`cat /sys/class/net/$1/statistics/rx_bytes`
        T1=`cat /sys/class/net/$1/statistics/tx_bytes`
        sleep 1
        R2=`cat /sys/class/net/$1/statistics/rx_bytes`
        T2=`cat /sys/class/net/$1/statistics/tx_bytes`
        TBPS=`expr $T2 - $T1`
        RBPS=`expr $R2 - $R1`
        TKBPS=`expr $TBPS / 1024`
        RKBPS=`expr $RBPS / 1024`
        echo "tx $1: $TKBPS kb/snrx $1: $RKBPS kb/s"
done

# 4.通过第三方工具”nload/ifstat/iftop”

参考网址：

• shell awk实现实时监控网卡流量脚本(常见应用二） – 程默
• Linux: Check Network Connection Command
• http://www.cyberciti.biz/networking/nload-linux-command-to-monitor-network-traffic-bandwidth-usage/
• http://www.apinglai.com/linux-%e7%9b%91%e6%8e%a7%e7%bd%91%e5%8d%a1%e5%ae%9e%e6%97%b6%e6%b5%81%e9%87%8f%e5%b8%a6%e5%ae%bd-%e8%84%9a%e6%9c%ac/
• Linux网络流量实时监控ifstat iftop命令详解 – ggjucheng