====== Using the STATE expression to write flexible plugins with check_multi ======

For a individual interpretation of data in //check_multi// the builtin state evaluation is a good means. It internally works with perl //eval// and therefore is extremely flexible.

Look at the following SNMP example as a simple introduction:
======  ======
<code perl>
# sensor.cmd
#
# (c) Matthias Flacke
# 30.12.2007
#
# Flexible interpretation of smmp results
command [ sensor ] = /usr/bin/snmpget -v 1 -c $COMMUNITY$ -Oqv $HOSTNAME$ XYZ-MIB::Sensor.0

state [ UNKNOWN  ] =  $sensor$  !~ /[4627859]/
state [ OK       ] = ( $sensor$ == 4 || $sensor$ == 6 )
state [ WARNING  ] = ( $sensor$ == 2 || $sensor$ == 7 || $sensor$ == 8 )
state [ CRITICAl ] = ( $sensor$ == 5 || $sensor$ == 9 )

</code>\\
\\ 
What is happening here?\\ The first part, the sensor command is just a plain snmpget, as you probably often use in self written plugins.\\ 
\\ 
But instead of a big if-else-clause //check_multi// uses state expressions to assign SNMP values to the different result values OK, WARNING and CRITICAL.\\
\\ 
UNKNOWN has a special role here. It is used, when the SNMP value is not member of a specific group of numbers.\\ 
\\ 
So this example really does not more than standard plugin also can do. But it shows how fast and reliable you can do develop such a SNMP plugin with //check_multi//. And if you want to change a value afterwards, you does not need to bother a developer. Any administrator can do this as well.\\ 
\\ 
//check_multi// can do all the standard tasks like a normal plugin: 
  * gathering data
  * validating the retrieved data (-> state [ UNKNOWN ] line)
  * evaluating the different results against rules 
\\ 
\\ 
{{tag>SNMP state plugin}}

~~LINKBACK~~
~~DISCUSSION|Comments~~