sar –n DEV 1 2

[sre@CDVM-213017031 ~]$ sar -n DEV 1 2
Linux 2.6.32-431.el6.x86_64 (CDVM-213017031)  05/04/2017  _x86_64_ (4 CPU)

08:05:30 PM  IFACE rxpck/s txpck/s rxkB/s txkB/s rxcmp/s txcmp/s rxmcst/s
08:05:31 PM  lo  0.00  0.00  0.00  0.00  0.00  0.00  0.00
08:05:31 PM  eth0 1788.00 1923.00 930.47 335.60  0.00  0.00  0.00

08:05:31 PM  IFACE rxpck/s txpck/s rxkB/s txkB/s rxcmp/s txcmp/s rxmcst/s
08:05:32 PM  lo  0.00  0.00  0.00  0.00  0.00  0.00  0.00
08:05:32 PM  eth0 1387.00 1469.00 652.12 256.98  0.00  0.00  0.00

Average:  IFACE rxpck/s txpck/s rxkB/s txkB/s rxcmp/s txcmp/s rxmcst/s
Average:   lo  0.00  0.00  0.00  0.00  0.00  0.00  0.00
Average:   eth0 1587.50 1696.00 791.29 296.29  0.00  0.00  0.00

#!/bin/bash

ethn=$1

while true
do
 RX_pre=$(cat /proc/net/dev | grep $ethn | sed 's/:/ /g' | awk '{print $2}')
 TX_pre=$(cat /proc/net/dev | grep $ethn | sed 's/:/ /g' | awk '{print $10}')
 sleep 1
 RX_next=$(cat /proc/net/dev | grep $ethn | sed 's/:/ /g' | awk '{print $2}')
 TX_next=$(cat /proc/net/dev | grep $ethn | sed 's/:/ /g' | awk '{print $10}')

 clear
 echo -e "t RX `date +%k:%M:%S` TX"

 RX=$((${RX_next}-${RX_pre}))
 TX=$((${TX_next}-${TX_pre}))

 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 "$ethn t $RX $TX "

done

[sre@CDVM-213017031 ~]$ cat /proc/net/dev
Inter-| Receive            | Transmit
 face |bytes packets errs drop fifo frame compressed multicast|bytes packets errs drop fifo colls carrier compressed
 lo:137052296 108029 0 0 0  0   0   0 137052296 108029 0 0 0  0  0   0
 eth0:13661574714188 31346790620 0 0 0  0   0   0 5097461049535 27671144304 0 0 0  0  0   0

Every 1.0s: ifconfig eth0Thu May 4 20:26:45 2017

eth0  Link encap:Ethernet HWaddr FA:16:3E:7E:55:D1
   inet addr:10.213.17.31 Bcast:10.213.23.255 Mask:255.255.248.0
   inet6 addr: fe80::f816:3eff:fe7e:55d1/64 Scope:Link
   UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
   RX packets:31350149703 errors:0 dropped:0 overruns:0 frame:0
   TX packets:27674701465 errors:0 dropped:0 overruns:0 carrier:0
   collisions:0 txqueuelen:1000
   RX bytes:13663400883450 (12.4 TiB) TX bytes:5098104759633 (4.6 TiB)