[mrtg] Re: Conversion code for hex to integer

[Dan Lynch]

Good suggestions (thanks Bill and Takumi), but I wonder what the values passed into my sub by MRTG are. When I capture the data with TCPdump, there doesn't seem to be dots encoded between values, only the hex itself. As in,
 
  0405D6DC20DE0D

When read by an interpreter like Ethereal, or an SNMP MIB browser application, the 0405 prefix is stripped off, and dots inserted:
 
  D6.DC.20.DE.0D

But in my PERL subroutine, the values look nothing like these examples. Here's my code right now:
 
  # Return an integer for a hex value
  open (STDERR, ">>error.txt");
  sub hextoint {
    my $value = shift;
    print STDERR $value,"\n";
    $value =~ y/\.//d;
    print STDERR $value,"\n";
    $value = hex ($value);
    print STDERR $value,"\n";
    return $value;
  }
 
And a recent output into error.txt:
 
   B*– 
   B*– 
  Illegal hexadecimal digit '****** ' ignored at (eval 6) line 21.
  0
   *& 
   *& 
  Illegal hexadecimal digit ' ' ignored at (eval 6) line 21.
  0
 
>From this it looks like what's being passed into the subroutine by MRTG isn't right. I've captured MRTG's SNMP conversation, and I know the returned value is hex as above. Does MRTG convert the result to printable ASCII before passing it to the subroutine? That might explain what I see.

More likely, my means of declaring it as a string ( <my $value = shift> ) is wrong. The PERL documentation for shift doesn't look like it does what I expect it to:
 
  Shifts the first value of the array off and returns it...
 
Yet the MRTG-reference doc uses this specifically under the ConversionCode section:
 
   # Return the length of the string argument
   sub Length2Int {
     my $value = shift;
     return length( $value );
   }

Thanks in advance for any help anyone can offer. As for me, it's back to the books.

Dan Lynch, CISSP
Information Technology Analyst
County of Placer
Auburn, CA


>>> Takumi Yamane <yamtak at b-session.com> 10/19/04 08:31PM >>>
On Tue, 19 Oct 2004 23:06:06 -0400 (EDT), "Bill Wichers" wrote 
in <3506.209.115.5.164.1098241566.squirrel at 209.115.5.164>:
> 
> >      40.05.D6.DC.20.DE.0D
> [snip]
> You need to write something that takes out the "." characters from 
> between the hex digits.

$val =~ s/\.//og;
or
$val =~ y/\.//d;

Regards,
Takumi Yamane <yamtak at b-session.com>

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