[mrtg] Problem with Negative Numbers

[Barber, Erik A.]

Unfortunately, MRTG doesn't support negative numbers (only positive
integers) without using RRDTool.

________________________________

From: mrtg-bounces at lists.oetiker.ch
[mailto:mrtg-bounces at lists.oetiker.ch] On Behalf Of Craig Metzer
Sent: Wednesday, April 18, 2007 10:53 AM
To: mrtg at lists.oetiker.ch
Subject: [mrtg] Problem with Negative Numbers


I'm trying to poll a satellite modem for Rx Signal Level.  The modem
returns a negative integer ten times the level (ex. -575 indicates the
level is -57.5 dBm).  I've configured a conversion function so I can log
the value returned by snmpget and compare it to the value in the log
file.  It appears that MRTG is not recognizing the number as negative.
It appears it is not recognizing the binary 1 MSD as a negative sign.

 

=========== 

Config file:

 

ConversionCode: functs.pl

 

Target[my-pub-sat-01-rsl]:
.1.3.6.1.4.1.6247.28.1.3.3.4.0&.1.3.6.1.4.1.6247.28.1.3.3.4.0:myROcs at my-
pub-sat-01.domain.gov|neg_int

 

==========

Functs.pl:

 

sub neg_int {

    my $n = shift;

    open FH, ">> rx_lvl.log";

#    my $o = (2^31 - $n) / 10;

    my $o = $n / 10;

    print FH localtime(time) . " -> IN: $n\tOUT: $o\n";

    close FH;

    return $o;

}

 

=========== 

Logs:

 

$head my-pub-sat-01-rsl.log

1176910486 2147483590 2147483590

1176910486 0 0 0 0

1176910186 0 0 0 0

1176909900 0 0 0 0

1176909600 0 0 0 0

1176909300 0 0 0 0

1176909000 0 0 0 0

 

$ cat rx_lvl.log

Wed Apr 18 16:29:46 2007 -> IN: -578    OUT: -57.8

Wed Apr 18 16:29:46 2007 -> IN: -578    OUT: -57.8

Wed Apr 18 16:34:46 2007 -> IN: -578    OUT: -57.8

Wed Apr 18 16:34:46 2007 -> IN: -578    OUT: -57.8

 


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