Applying a multiplier to check_snmp results

[Gary Every]

You can add an executable to your snmpd.conf file to execute your snmpget
locally, receive the output and modify it to your heart's content. To run
executables:

-- On your nagios server:
<path_to_plugins>/check_snmp -H <HOSTADDRESS> -C
<your_snmp_community_string>  -o
enterprises.ucdavis.extTable.extEntry.extResult.<###>,enterprises.ucdavis.extTable.extEntry.extOutput.<###>
-w 0 -c 1

The variables you'll need to supply are:
<HOSTADDRESS>  - The IP of the remote host
<snmp_community_string> - Self-explanatory
<###> - The number of the "exec" in snmpd.conf (see below)

-- On your remote server
In /etc/snmp/snmpd.conf:
<snip>
exec GENERIC_NAME_OF_CHECK /usr/local/bin/modify_output.sh

</snip>
## If the above line is the only 'exec' directive in your snmpd.conf, then
the <###> above will be a 1, if it's the third exec directive, it will be a
3, and so on....

Now, in /usr/local/bin/modify_output.sh
<snip>
!#/bin/bash

## Execute your snmpget here and capture it in a variable
output=`snmpget -v 1 -c public localhost .enterprises.6347.1.1.17 -O Qve`
## $output now should hold something akin to 20717 or whatever the actual
output is

## Check for zero
if [ "$output" = "0" ]
then
## Some error here:
echo "OOPS! This is zero. Why?"
exit 1
fi

## Ok, it's not zero, divide by 100 or multiply by .01
modified_output=`expr $output \* .01` ## Note the backslash escaping the *
echo $modified_output
</snip>

Restart snmpd

Now, from nagios, run the command above, which will call out to the snmpd
server on the remote host, find the <###>th 'exec' entry in snmpd.conf,
execute the shell script, and return whatever you echo out from within your
shell script.

Remember that check_snmp only returns one line, so any line breaks, etc will
be lost when it's run from the nagios server.

Hope this helps!
g.;


On Thu, Aug 12, 2010 at 3:48 PM, Hall, JC <jhall at iodatacenters.com> wrote:

> I certainly wish I could do that.  I'm just a novice.
>
> I can basically accomplish what I want (in regards to multiplying the
> output) with snmpget.
>
> printf "scale=2;%d*0.01\n" $(snmpget -v 1 -c public 192.168.104.37
> .enterprises.6347.1.1.17 -O Qve)|bc
>
> 208.72
>
> Any thoughts surrounding how I could run this as an external command and
> pipe it back into nagios?
>
> -----Original Message-----
> From: Matthew J. Salerno [mailto:vagabond_king at yahoo.com]
> Sent: Thursday, August 12, 2010 2:17 PM
> To: Nagios Users List
> Subject: Re: [Nagios-users] Applying a multiplier to check_snmp results
>
> I ran into the same thing, I ended up writing my own plugins.  Just look
> for a
> non binary plugin (perl/python etc) and then hack away.
>
>
>
> ----- Original Message ----
> From: Jim Avery <jim at jimavery.me.uk>
> To: Nagios Users List <nagios-users at lists.sourceforge.net>
> Sent: Thu, August 12, 2010 5:05:42 PM
> Subject: Re: [Nagios-users] Applying a multiplier to check_snmp results
>
> On 12 August 2010 21:27, Hall, JC <jhall at iodatacenters.com> wrote:
> > I have a situation where I would like to apply a multiplier to the
> results
> > of a check_snmp output.
> >
> > The situation is this:
> >
> > The value received from my check_snmp = 20717.  The integer multiplier
> for
> > this particular OID is 0.01.
> >
> > The output I want reported to Nagios is 20717 x 0.01 = 207.17.
> >
> > Looking through the options of the check_snmp plugin, I can’t determine
> how
> > I could accomplish this.
> >
> >
> >
> > Any thoughts are appreciated.
>
>
> +1 to that!
>
> I was doing some monitoring on a UPS yesterday and found the current
> is given as an integer which is 10x the Amps, so it would be great to
> be able to divide by 10 (or multiply by whatever) in check_snmp.
>
>
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-- 
Gary Every
"Pay it Forward!"
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