Simple netstat bandwidth summary script

This is a simple script for showing the bandwidth usage on all your network interfaces using netstat. It displays the total usage per interface and an approximation of the usage per day and month.

Uptime 2 days 22:49, Sun Aug  9 15:46:25 CEST 2009 
Iface    Rx Total     Tx Total       Rx/day       Tx/day     Rx/month     Tx/month   Rx+Tx/month
             (GB)         (GB)         (MB)         (MB)         (GB)         (GB)         (GB)
lo0           .03          .03        10.86        10.86          .32          .32          .65
en1          2.48          .15       841.32        52.56        25.23         1.57        26.81

#!/bin/sh
# 
# Shows network bandwidth usage.
# 
# Copyright (c) 2009 by alexyu.se. All rights reserved.
#
# This program is free software: you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation, either version 2 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#

function printHeader ()
{
	printf "Uptime `uptime | awk '{if ($4 == "days," || $4 == "day,") print $3,$4,$5; else if ($4 == "mins,") print $3,$4; else print $3 " hours "}' | sed s/,//`"
	printf " `date` \n"
	printf "%-5s  " "Iface"
	printf "%10s   " "  Rx Total"
	printf "%10s   " "  Tx Total"
	printf "%10s   " "Rx/day"
	printf "%10s   " "Tx/day"
	printf "%10s   " "Rx/month"
	printf "%10s   " "Tx/month"
	printf "%10s\n" "Rx+Tx/month"
	
	printf "%-5s  " " "
	printf "%10s   " "(GB)"
	printf "%10s   " "(GB)"
	printf "%10s   " "(MB)"
	printf "%10s   " "(MB)"
	printf "%10s   " "(GB)"
	printf "%10s   " "(GB)"
	printf "%10s\n" "(GB)"	
}

function printSummary ()
{
	printf "%-5s  " $INTERFACE_NAME
	printf "%10s   " $(echo "scale=2; $TOTAL_IN/1000000000" | bc) 
	printf "%10s   " $(echo "scale=2; $TOTAL_OUT/1000000000" | bc) 
	printf "%10s   " $(echo "scale=2; $TOTAL_IN*86400/$UPTIME_SECS/1000000" | bc)  
	printf "%10s   " $(echo "scale=2; $TOTAL_OUT*86400/$UPTIME_SECS/1000000" | bc) 
	printf "%10s   " $(echo "scale=2; $TOTAL_IN*86400*30/$UPTIME_SECS/1000000000" | bc) 
	printf "%10s   " $(echo "scale=2; $TOTAL_OUT*86400*30/$UPTIME_SECS/1000000000" | bc) 
	printf "%10s\n" $(echo "scale=2; ($TOTAL_OUT+$TOTAL_IN)*86400*30/$UPTIME_SECS/1000000000" | bc)	
}

UPTIME_SECS=`uptime | awk '{ split($3,b,":"); split($5,a,":"); if (a[2] == 0) print b[1]*86400+(a[1]*60); else print b[1]*86400+a[1]*3600+a[2]*60}'`
INTERFACES=`netstat -b -i | awk '{if ($5 > 0 && $8 > 0) print $1,$7,$10}' | grep -i -v name | uniq`

printHeader

for i in $INTERFACES
do
	(( count++ ))
	if (($count % 3 == 1))
	then
		INTERFACE_NAME=$i
	elif (($count % 3 == 2));
	then
		TOTAL_IN=$i
	elif (($count % 3 == 0));
	then
		TOTAL_OUT=$i
	printSummary $INTERFACE_NAME $TOTAL_IN $TOTAL_OUT
	fi
done