#!/usr/bin/perl

# displays to stdout the bandwidth use of a interface

$alive = 1;

$SIG{'INT'} = sigshut;
$SIG{'TERM'} = sigshut;


while($alive) {
	sleep(1);

	open(IFC,"/sbin/ifconfig eth6|");
	while($in = <IFC>) {
		if(($x) = $in =~ /.*RX bytes:(\d+).*/) {
			$rxt = $rxd;
			$rxd = $x;
		}
		if(($x) = $in =~ /.*TX bytes:(\d+).*/) {
			$txt = $txd;
			$txd = $x;
		}
	}
	close(IFC);

	next if(!$rxt || !$txt);

	$rxsec = $rxd - $rxt;
	$txsec = $txd - $txt;

	$rxformat = bwformat($rxsec);
	$txformat = bwformat($txsec);

	print "rx: $rxformat tx: $txformat\n";

}



sub sigshut {
	$alive = 0;
}

sub bwformat {
	$a = shift;
	
	if($a < 1024) {
		return "$a bits/s";
	} elsif ($a < (1024 * 1024)) {
		return int($a / 1024) . " kbits/s";
	} else {
		return $a / (1024 * 1024) . " mbits/s";
	}

	return "NaN";

}