netmon.sh

#!/bin/bash

INTERVAL="1"  # update interval in seconds

if [ -z "$1" ]; then
        echo
        echo usage: $0 [network-interface]
        echo
        echo e.g. $0 eth0
        echo
        echo shows packets-per-second, bytes-per-second, drops-per-second
        exit
fi

IF=$
D=`date +%H:%M:%S`
printf "%s %+7s %+7s %+10s %+10s %+8s %+8s\n" $D tx-MB rx-MB tx-packets rx-packets tx-drops rx-drops

while true
do
	D=`date +%H:%M:%S`
        A1=`cat /sys/class/net/$1/statistics/rx_packets`
        B1=`cat /sys/class/net/$1/statistics/tx_packets`
        C1=`cat /sys/class/net/$1/statistics/rx_bytes`
        D1=`cat /sys/class/net/$1/statistics/tx_bytes`
   E1=`cat /sys/class/net/$1/statistics/rx_dropped`
        F1=`cat /sys/class/net/$1/statistics/tx_dropped`

        sleep $INTERVAL
        A2=`cat /sys/class/net/$1/statistics/rx_packets`
        B2=`cat /sys/class/net/$1/statistics/tx_packets`
        C2=`cat /sys/class/net/$1/statistics/rx_bytes`
        D2=`cat /sys/class/net/$1/statistics/tx_bytes`
        E2=`cat /sys/class/net/$1/statistics/rx_dropped`
        F2=`cat /sys/class/net/$1/statistics/tx_dropped`
        MB=1048576
   TXPPS=`expr $B2 - $B1`
        RXPPS=`expr $A2 - $A1`
        TXBPS=`bc -l <<< "scale=2;($D2 - $D1) / $MB"`
        RXBPS=`bc -l <<< "scale=2;($C2 - $C1) / $MB"`
        TXDRP=`expr $F2 - $F1`
        RXDRP=`expr $E2 - $E1`
        #echo -e "$TXBPS\t\t$RXBPS\t\t$TXPPS\t\t$RXPPS\t\t$TXDRP\t\t$RXDRP"
   printf "%s %+7s %+7s %+10s %+10s %+8s %+8s\n" $D $TXBPS $RXBPS $TXPPS $RXPPS $TXDRP $RXDRP
done