Hi Terry, ----- On May 11, 2017, at 1:21 AM, Terry Kennedy [email protected] wrote:
> http://oss.oetiker.ch/mrtg/doc/mrtg-reference.en.html says (under > Multi Target Syntax) that " Any syntactically correct expression that > the Perl interpreter can evaluate to will work" and gives an example > of adding two targets together (which does work). However, I have > been unable to get the reverse (subtraction) to work. Am I doing some- > thing wrong, or is this a documentation error or a programming over- > sight? > > To complicate matters a bit, I also need to swap the In/Out values > on the interface being subtracted (as in the "Reversing" section of > the manual). I have not attempted this yet, but am wondering if MRTG > is mis-interpreting the minus sign when working with Multi Target Syn- > tax. And I'm perplexed by how I would actually put this into the MRTG > configuration file - I'm coming up with something like: > > 1:public@switchA:::::2 - -2:public@switchA:::::2 > > which is pretty arcane. > > In case you're wondering "why would anybody want to do that", here > is the usage case: I have a customer with a link to us which carries > both traffic he pays me for, as well as traffic we send to another > interface (to a different upstream) for a fixed fee. The goal is to > graph "customer input minus upstream output" and "customer output > minus upstream input", to give a graph that represents only traffic > he is paying us for. > > Right now I have a pretty horrible external script to accomplish > this (available on request), but from reading the documentation, all > of the pieces to do it inside MRTG should already exist, if I can > figure out how to combine them. the problem ist that you are adding a '-' infront of the interface number you have to use whitespace ... the following should work 1:public@switchA:::::2 - ( 0 - 2:public@switchA:::::2 ) BUT then again ... a - ( 0 - b ) = a + b ... so I am not quite sure what you try to do ... cheers tobi > Terry Kennedy http://www.glaver.org New York, NY USA > > _______________________________________________ > mrtg mailing list > [email protected] > https://lists.oetiker.ch/cgi-bin/listinfo/mrtg -- Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland www.oetiker.ch [email protected] +41 62 775 9902 _______________________________________________ mrtg mailing list [email protected] https://lists.oetiker.ch/cgi-bin/listinfo/mrtg
