# [mrtg] Re: operations on OIDs

WEYMIENS Bruno FTRD/DMI/SOP bruno.weymiens at rd.francetelecom.com
Tue Oct 2 18:04:33 MEST 2001

```hi again,

- 1st mistake : I wanted to divide by 2.000.000, so the result would have
been between 0 and 1 (decimal number !), and so I suppose MRTG would have
always graphed 0 ; so I had to multiply the result by 100
- 2nd : without parenthesis, I was calculating (cf Richard Bragg's answer
below) : a+(b/c), so a result near 0 (b<<c)

now, dividing by 20.000, and adding parenthesis, the result is between 0 and
100 !

Great !
Thanx to all

-----Message d'origine-----
De : Richard Bragg [mailto:Richard.Bragg at ntl.com]
Envoyé : mardi 2 octobre 2001 17:25
À : 'WEYMIENS Bruno FTRD/DMI/SOP'; 'Paul C. Williamson';
mrtg at list.ee.ethz.ch
Objet : RE: [mrtg] operations on OIDs

In maths multiplication/division has priority over addition/subtraction.

What you are doing is

a+(b/c)  the parenthesis are implied.  You want to explicitly do
(a+b)/c as you rightly guessed.

-----Original Message-----
From: WEYMIENS Bruno FTRD/DMI/SOP
[mailto:bruno.weymiens at rd.francetelecom.com]
Sent: 02 October 2001 16:10
To: 'Paul C. Williamson'; mrtg at list.ee.ethz.ch
Subject: [mrtg] operations on OIDs

hi,

I'd like to have help ("indeed ?") :
- I'd like to graph the % of an interface's load, ie. the sum of the
ifInOctets & the ifOutOctets, divided by the maximum throughput
- I suceeded in summing the ifInOctets & the ifOutOctets, writing smthg like
:
.1.3.6.1.2.1.2.2.1.10.1&.1.3.6.1.2.1.2.2.1.10.1:com at a.b.c.d +
.1.3.6.1.2.1.2.2.1.16.1&.1.3.6.1.2.1.2.2.1.16.1:com at a.b.c.d
- I divided this by 2.000.000 (maximum througput), so writing :
.1.3.6.1.2.1.2.2.1.10.1&.1.3.6.1.2.1.2.2.1.10.1:com at a.b.c.d +
.1.3.6.1.2.1.2.2.1.16.1&.1.3.6.1.2.1.2.2.1.16.1:com at a.b.c.d / 2000000,
and now all = zero.

should I add parenthesis before division ?
is there a more simple way to do it ?
I looked at the faq.mrtg.org, but there's nothing for 'mathematical',
neither 'operations'...

regards

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