Newbie: How to calculate within Nagios?

[Zembower, Kevin]

I've just gotten my first Nagios system set up and running, so if this
is a common question, please forgive me and point out what I overlooked.

I want to use Nagios and the check_snmp plug-in to monitor the ambient
temperature in my server room, and send alerts when the air conditioner
fails. My Dell PowerEdge servers have an ambient temperature probe that
reports in tenths of a degree Celsius. Here's an example:

kevinz at cn2:~$ /usr/lib/nagios/plugins/check_snmp -H 10.253.192.204 -o
.1.3.6.1.4.1.674.10892.1.700.20.1.6.1.3
SNMP OK - 240 | iso.3.6.1.4.1.674.10892.1.700.20.1.6.1.3=240  
kevinz at cn2:~$

The output indicates that the temperature is 24 degrees Celsius or
(9/5)*24+32=75.2 degrees Fahrenheit. I'd like to use the Fahrenheit
value in my emails, and set warning and critical values such as:

kevinz at cn2:~$ /usr/lib/nagios/plugins/check_snmp -H 10.253.192.204 -o
.1.3.6.1.4.1.674.10892.1.700.20.1.6.1.3 -w :220 -c :225
SNMP CRITICAL - *230* | iso.3.6.1.4.1.674.10892.1.700.20.1.6.1.3=230  
kevinz at cn2:~$

(These are artificially low, just for testing.)

My question is, should I just hard-code the values in the email message
("Warning: the server room temperature exceeds 80 F.") or could I
calculate within Nagios and say "Warning: the server room temperature is
XX F." If I can calculate within Nagios, please point out an example in
the documentation or other source.

Thanks for your suggestion. I really appreciate all the time and effort
devoted to Nagios.

-Kevin

Kevin Zembower
Internet Services Group manager
Center for Communication Programs
Bloomberg School of Public Health
Johns Hopkins University
111 Market Place, Suite 310
Baltimore, Maryland  21202
410-659-6139 

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