下面是我的wlan0网卡的输出信息，你可以使用ifconfig 或者 ifconfig | sed -n ‘/wlan0/,10p‘ 获取显示的信息的格式
wlan0 Link encap:Ethernet HWaddr xx:xx:xx:xx:xx:xx
inet addr:172.29.164.251 Bcast:172.29.167.255 Mask:255.255.248.0
inet6 addr: 2001:da8:c803:4a57:e190:606f:3155:9369/64 Scope:Global
inet6 addr: fe80::6e71:d9ff:fe0b:27f6/64 Scope:Link
inet6 addr: 2001:da8:c803:4a57:6e71:d9ff:fe0b:27f6/64 Scope:Global
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1305 errors:0 dropped:0 overruns:0 frame:0
TX packets:647 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:370741 (362.0 KiB) TX bytes:117872 (115.1 KiB)
下面的脚本通过获取最后一行的RX、TX的信息，在两个时间点上获取，然后统计这一段时间内的总流量。
最后打印输出统计信息在屏幕上。
#!/bin/bash
#network traffic statistics
#Write by Ricardo.su 2015-04-30
TIME_RANGE=10
time=`date +%m"-"%d" "%k":"%M`
rx_point_1=`ifconfig wlan0 | grep [[:space:]]RX.*TX | awk ‘{print $2}‘ | cut -c7-`
tx_point_1=`ifconfig wlan0 | grep [[:space:]]RX.*TX | awk ‘{print $6}‘ | cut -c7-`
sleep $TIME_RANGE
rx_point_2=`ifconfig wlan0 | grep [[:space:]]RX.*TX | awk ‘{print $2}‘ | cut -c7-`
tx_point_2=`ifconfig wlan0 | grep [[:space:]]RX.*TX | awk ‘{print $6}‘ | cut -c7-`
rx_rs=$(((rx_point_2-rx_point_1)/1024))
tx_rs=$(((tx_point_2-tx_point_1)/1024))
echo "Date $time"
echo "Average Network Traffic in $TIME_RANGE s: RX $rx_rs KB TX $tx_rs KB"