[mrtg] Re: Overcoming divide by zero exceptions

Alex van den Bogaerdt alex at ergens.op.het.net
Mon Dec 13 23:40:25 MET 2004

On Mon, Dec 13, 2004 at 02:26:29PM -0800, Tendolkar Mohit wrote:

> I'm using MRTG to plot the value of target expressions that are made of
> multiple OIDs, such as percentage of some items.

Per cent -> one for every hundred.

There's no way this can result in a division by zero.

> However, in certain contexts, the values of the actual SNMP counters
> used in the expression are zero - which is also a valid condition: thus
> even for a perfectly legitimate expression, while evaluating the value
> of the target expression, perl/mrtg may encounter a divide by zero
> exception.

I seriously doubt this.  Please elaborate so we can check your logic.

> If so, is there a way to instruct MRTG to evaluate the expression only
> if it makes sense (the denominator evaluates to a non-zero values)?

As always: The external program interface is your friend.

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