#!/usr/bin/perl -w

my $etime=0;
my $eth0in="";
my $eth0out="";
my $lo="";
my $petime=0;
my $peth0in=0;
my $peth0out=0;
my $plo=0;
my $tmp=0;
my $i=0;
my $n=1;

#NOTE!!! snmp counters reset at 4,294,967,295!

for (;;) {
   $i=$i+1;
   $etime=time;

   system("snmpwalk localhost public interfaces.ifTable.ifEntry.ifInOctets.3 >/tmp/eth0in");
   system("snmpwalk localhost public interfaces.ifTable.ifEntry.ifOutOctets.3 >/tmp/eth0out");
   system("snmpwalk localhost public interfaces.ifTable.ifEntry.ifOutOctets.1 >/tmp/loout");

   open(fileIN,"/tmp/eth0in") or die("Cannot open /tmp/eth0in: $!");
   my @fileData = <fileIN>;
   close(fileIN);

   foreach $line (@fileData)
   {
       chomp($line);
       $eth0in=substr($line,54,10);
   }

   open(fileIN,"/tmp/eth0out") or die("Cannot open /tmp/eth0out: $!");
   @fileData = <fileIN>;
   close(fileIN);

   foreach $line (@fileData)
   {
       chomp($line);
       $eth0out=substr($line,54,10);
   }

   open(fileIN,"/tmp/loout") or die("Cannot open /tmp/loout: $!");
   @fileData = <fileIN>;
   close(fileIN);

   foreach $line (@fileData)
   {
       chomp($line);
       $lo=substr($line,54,10);
   }

   $eth0out = 0 + $eth0out;
   $eth0in  = 0 + $eth0in;
   $lo      = 0 + $lo;

   #time
   $tmp=$etime;
   $etime=$etime-$petime;
   $petime=$tmp;

   #eth0in
   if ($eth0in<$peth0in) { #the counter was reset
      $tmp=$eth0in;
      $eth0in=$eth0in + 4294967295;
      $eth0in=$eth0in-$peth0in;
      $eth0in=$eth0in/$etime;
      $eth0in=$eth0in/8; #bytes per second
      $peth0in=$tmp;
   } else {
      $tmp=$eth0in;
      $eth0in=$eth0in-$peth0in;
      $peth0in=$tmp;
      $eth0in=$eth0in/$etime;
      $eth0in=$eth0in/8; #bytes per second
   }

   if ($eth0out<$peth0out) { #the counter was reset
      $tmp=$eth0out;
      $eth0out=$eth0out + 4294967295;
      $eth0out=$eth0out-$peth0out;
      $eth0out=$eth0out/$etime;
      $eth0out=$eth0out/8; #bytes per second
      $peth0out=$tmp;
   } else {
      $tmp=$eth0out;
      $eth0out=$eth0out-$peth0out;
      $peth0out=$tmp;
      $eth0out=$eth0out/$etime;
      $eth0out=$eth0out/8; #bytes per second
   }

   #lo
   if ($lo<$plo) { #the counter was reset
      $tmp=$lo;
      $lo=$lo + 4294967295;
      $lo=$lo-$plo;
      $lo=$lo/$etime;
      $lo=$lo/8; #bytes per second
      $plo=$tmp;
   } else {
      $tmp=$lo;
      $lo=$lo-$plo;
      $plo=$tmp;
      $lo=$lo/$etime;
      $lo=$lo/8; #bytes per second
   }

   open(fileOUT, ">int.php") or dienice("Can't open log.txt for writing: $!");
      print fileOUT "<?php\n\$eth0in=\"$eth0in\";\n\$eth0out=\"$eth0out\";\n\$lo=\"$lo\";\n?>\n";
   close(fileOUT);

   $etime=time;
   if ($n!=1) {system("rrdupdate sysgraphint.rrd $etime:$eth0in:$eth0out:$lo");}
   $n=$n+1;
   sleep(30);
}