#!/usr/bin/perl
#
# BWMon
# William Riley  williams.workbench@gmail.com

use strict;
use warnings;
use Getopt::Long;
use Pod::Usage;

my ($verbose, $quiet, $help, $man, $interface, $interval);
my($rx_last,$tx_last,$rx,$tx,$first);
my $result = GetOptions( "verbose" => \$verbose, "help" => \$help, "man" => \$man, "quiet" => \$quiet,
	"interface=s" => \$interface, "interval=n" => \$interval ) or pod2usage(2);
pod2usage(-exitstatus => 0, -verbose => 2) if $man;
if($help) {
    pod2usage(2);
}

$rx_last = 0;
$tx_last = 0;
$rx = 0;
$tx = 0;
$first = 1;

$interface or $interface = "eth0";
$interval or $interval = 1;

while(1){
	open INTERFACE, "/sbin/ifconfig $interface|" or die "Could not open $interface";
	while(<INTERFACE>){
		my $line = $_;
		chomp $line;
		if($line =~ m/RX bytes:([\d]+).*TX bytes:([\d]+)/){
			if($first == 1){
				printf "Timestamp,Interface,RX Bytes/Sec,TX Bytes/Sec\n";
				$first = 0;
				$rx_last = $1;
				$tx_last = $2;
			}else{
				$rx = $1 - $rx_last;
				$tx = $2 - $tx_last;
				my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst)=localtime(time);
				my $timestamp = sprintf("%04d-%02d-%02d %02d:%02d:%02d", $year + 1900, $mon, $mday + 1,$hour,$min,$sec);
				printf "%s,%s,%d,%d\n", $timestamp, $interface, $rx / $interval, $tx / $interval;
				
				$rx_last = $1;
				$tx_last = $2;
			}
		}
	}
	close INTERFACE;
	sleep $interval;
}

exit 0;

__END__

=head1 NAME

BWMon - Bandwidth monitor

=head1 SYNOPSIS

BWMon [options]

    Options:
	--interface	interface to watch (default eth0)
	--interval	how often to check (default 1 second)
        --help          brief help message
        --man           full documentation

=head1 OPTIONS

=over 12

=item B<--interface>

Which interface to watch, i.e. eth0

=item B<--interval>

Gather interface statistics every <interval> seconds

=item B<--help>

Print a brief help message and exit.

=item B<--man>

Print the manual page and exit.

=back

=head1 DESCRIPTION

Monitor the bandwidth on a given interface and report the bytes per second

=head1 CHANGELOG

June 15, 2007  William Riley  williams.workbench@gmail.com

=cut