#!/bin/bash

varName="novalue"
varDefault=""
myDelim=" "
myField=""

do_help() {
cat << HELP_EOF
This utility is designed to be called by the ARGx parameters of a Nagios configuration as follows:

  \$\$(\$USER1\$/env -n <var> [-t <default>] [-f <field>] [-d <delim>]

Where:

  var     is the name of a NAGIOS_variable (see https://assets.nagios.com/downloads/nagioscore/docs/nagioscore/4/en/macrolist.html) (case insensitive)
  default is a default value if \$NAGIOS_var\$ is blank (case sensitive)
  word    is an awk-compatible field number (potentially to use with <delim>)
  delim   is an awk-compatible field delimiter (defaults to space)

The value will always be trimmed of leading and/or trailing spaces/tabs.

If -f is used, then the result will be as if the request were:

  eche \$NAGIOS_var\$ | awk -F <delim> '{print $<field>}'

Examples:

  .../env -n servicedesc
    Will return "Root Partition" (or whatever the service check is named)
  .../env -n hostName
    Will return "localhost" (or whatever the name of the host is that ran the check)
  .../env -n SERVICESTATE -t 0
    Will return the current state of the service (0, 1, 2) or 0 if the state is not defined
  .../env -n servicedesc -d : -f 2
    If the service name is "MySQL Check: myDatabase" then it will return "myDatabase" (trimmed)

HELP_EOF
}

while [ -n "$1" ]; do
  case "$1" in
    -n) varName=`echo "NAGIOS_$2" | tr "a-z" "A-Z"`; shift 2;;
    -t) varDefault="$2"; shift 2;;
    -d) myDelim="$2"; shift 2;;
    -f) myField="$2"; shift 2;;
    *) shift 1;;
  esac
done

# If we don't have a config file, then we don't have variables
if [ -f "$NAGIOS_MAINCONFIGFILE" ]; then
  varValue="${!varName}"
  [ -n "$varValue" -a -n "$myField" ] && varValue=`echo "$varValue" | awk -F "$myDelim" --assign f="$myField" '{print $f}'`
fi
[ -z "$varValue" ] && varValue="$varDefault"
varValue=`echo $varValue | sed -e "s/^[ \t]*//" -e "s/[ \t]*$//"`
  
echo "$varValue"

exit 0