#! /usr/bin/perl
# $Id$

use strict;
use warnings;

my($IFDEV,$SECS)=@ARGV;

$SECS||=8;
my $IGNORE=qr/^(?:lo|sit|pan|tun|tap|wmaster|sixxs|virbr)\d*$/;

$|=1;
# $if->{"rx"=>,"tx"=>}
my %last;
my $last_if="";
my $dot;
for (;;) {
	local *F;
	open F,"/proc/net/dev" or die;
	my $dev=do { local $/; <F> or die; };
	close F or die;
	$dev=~s/^Inter-.*\n face .*\n// or die $dev;
	my $smth;
	while ($dev=~s/^\s*(\S+?):\s*(\d+)(?:\s+\d+){7}\s+(\d+)\s.*\n//) {
		my($if,$rx,$tx)=($1,$2,$3);
		next if $IFDEV && $if ne $IFDEV;
		next if !$IFDEV && $if=~/^$IGNORE$/o;
		$last{$if}||={};
		my $last=$last{$if};
		if (defined $last->{"rx"}) {
			if ($dot) {
				print "\n";
				$dot=0;
			}
			if ($last_if ne $if) {
				$last_if=$if;
				print "$if:\n";
			}
			# FIXME - done?
			# 1798512 37387
			# 2147483648      32058
			# 1800104 35797
			sub fmt($$)
			{
				my($now,$last)=@_;
				if ($now>=$last) {
					return $now-$last;
				} else {
					return "=$now";
				}
			}
			print fmt($rx,$last->{"rx"})."\t".fmt($tx,$last->{"tx"})."\n";
		}
		$last->{"rx"}=$rx;
		$last->{"tx"}=$tx;
		$smth++;
	}
	die $dev if $dev;
	if (!$smth) {
		print ".";
		$dot++;
		$last_if="";
	}
	sleep $SECS;
}