service_monitoring_via_systemctl.txt

Service monitoring using systemctl, convert string to number, RegEx
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This document represents the following zabbix features/techniques:

* UserParameter which will discover all services. JSON format containing 2 parameters {#NAME} and {#STATUS}
* Item UserParameter with argument. A safest way (rather than use system.run) to call a custom command from item key
* A textual item. This is the input data (raw contet). A result from "systemctl status some-service-name". You do not want to store this in database
* A dependable item. By grabing the raw conted and using regular expression it is possible to extract a line. See item prototypes: "active {#NAME}" and "loaded {#NAME}".
  This technique show how it is possible to conver string to numbers. Underneath the hood it is not a substition. 
  
  
First step: The recieving value is one word like "disabled" or "enabled"
case1: disabled
case2: enabled
case3: static

Now we need to add to each of result all avaiable options. At first we will put this string in group 1:
(.*)
now will print on screen this group 1 + add all available options.
\1:disabled=0:enabled=1:static=2
This is necessary because in the last step we want for the regEx to allways found at least on of the keywords.

now the result on screen will because
case1: disabled:disabled=0:enabled=1:static=2
case2: enabled:disabled=0:enabled=1:static=2
case3: static:disabled=0:enabled=1:static=2

It does not make sence! right? What can we possible do with this string?
The answer is to use first group as an input of second group
(disabled|enabled|static)(?=.*:\1=(\d))
Inside the first group there can be only words "disabled", "enabled" or "static"