#!/usr/bin/perl -w
# check_temperature: Nagios wrapper script around digitemp.
# Used to monitor a couple of 1-wire temperature sensors and to raise an
# alarm when one of them reports a temperature outside a predefined band.
# For more information: http://www.hoppie.nl/tempsens .

# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to
# deal in the Software without restriction, including without limitation the
# rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
# sell copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
# IN THE SOFTWARE.
#
# Howto Install in Nagios (tested with v1.3)
#
# 0. Make sure that Digitemp works and temperatures are written to the file:
#    /var/lib/temperature/current
#    as described at http://www.hoppie.nl/tempsens/ .
#
# 1. Copy this Perl script to /usr/local/nagios/libexec/ or wherever you have
#    placed your Nagios plugins.
#
# 2. Add a command to /usr/local/nagios/etc/checkcommands.cfg like this:
#
#    # DigiTemp temperature check command
#    define command {
#      command_name check_temperature
#      command_line /usr/local/nagios/libexec/check_temperature \
#                   -s $ARG1$ -t $ARG2$ -w $ARG3$ -c $ARG4$
#      (fold the above into one line)
#    }
#
# 3. Tell Nagios to monitor the temperature by adding a service line like
#    this to your service.cfg file:
#
#    # DigiTemp Temperature check Service definition
#    define service {
#        use                             generic-service
#        host_name                       kermit
#        service_description             Temperature
#        is_volatile                     0
#        check_period                    24x7
#        max_check_attempts              3
#        normal_check_interval           5
#        retry_check_interval            2
#        contact_groups                  home-admins
#        notification_interval           240
#        notification_period             24x7
#        notification_options            w,u,c,r
#        check_command                   check_temperature!1!25!3!5
#    }
#
#    In this example,
#      1 is the sensor # (as reported by digitemp -a) to monitor
#     25 is the target (ideal) temperature
#      3 is the warning temperature deviation from the target
#      5 is the critical temperature deviation from the target

# ===========================================================================

# Modules to use.
use strict;
use Getopt::Std;

# Define all our variables.
use vars qw($temperature_state
            $opt_s $opt_t $opt_w $opt_c
            $sensor $target $warn_dev $crit_dev
	    $temperature
            %exit_codes);

# Place to look for the temperature state file (may be customised here).
$temperature_state = '/var/lib/temperature/current';

# Predefined exit codes for Nagios.
%exit_codes   = ('UNKNOWN' ,-1,
                 'OK'      , 0,
                 'WARNING' , 1,
                 'CRITICAL', 2,);

# Get the options
if ($#ARGV le 0)
{
  &usage;
} else {
  getopts('s:t:w:c:');
}

# Shortcircuit the switches
if (!$opt_w or $opt_w == 0 or !$opt_c or $opt_c == 0)
{
  print "*** You must define WARNING and CRITICAL deviation bands!\n";
  &usage;
}

# Check if levels are sane
if ($opt_w >= $opt_c)
{
  print "*** WARNING deviation band must not be greater than CRITICAL!\n";
  &usage;
}

# Default sensor to read is #0
if(!$opt_s)
{
  $sensor = 0;
} else {
  $sensor = $opt_s;
}

# Default target temperature is 20 (degrees Centigrade).
if(!$opt_t)
{
  $target = 20;
} else {
  $target = $opt_t;
}

$warn_dev = $opt_w;
$crit_dev = $opt_c;

# Read the output from digitemp, as plain temperature Centigrade.
# In order to avoid race conditions, a separate cron job usually placed in
# /usr/local/bin/get_temperature polls digitemp and leaves the most recent
# poll list in /var/lib/temperature/current . We just need to fetch the
# correct line out of this file to get the digitemp output.

# Does the file exist and is it readable?
if (!-r $temperature_state) {
  print "Could not read file $temperature_state; aborting.\n";
  exit $exit_codes{'UNKNOWN'};
}

open( DIGITEMP, $temperature_state );
$temperature = -9999;
while( <DIGITEMP> )
{
  chomp;
  # Select only the correct line.
  if( $_ =~ /Sensor $sensor/i )
  {
    # Extract the temperature in Centigrade.
    /Sensor [0-9] C: ([0-9.]+)/;
    $temperature = $1;
    last;
  }
}
close( DIGITEMP );

# Was the requested sensor temperature available in the state file?
if( $temperature==-9999 )
{
  # No!
  print "No data found for sensor #$sensor\n";
  exit $exit_codes{'UNKNOWN'};
}

# Now for the real checks.
if( $temperature and abs($target-$temperature) >= $crit_dev )
{
  print "Temperature CRITICAL - Sensor #$sensor = $temperature C\n";
  exit $exit_codes{'CRITICAL'};
} elsif ($temperature and abs($target-$temperature) >= $warn_dev ) {
  print "Temperature WARNING - Sensor #$sensor = $temperature C\n";
  exit $exit_codes{'WARNING'};
} elsif( $temperature ) {
  print "Temperature OK - Sensor #$sensor = $temperature C\n";
  exit $exit_codes{'OK'};
} else {
  print "Error parsing result for sensor #$sensor\n";
  exit $exit_codes{'UNKNOWN'};  
}

# Show usage
sub usage()
{
  print "check_temperature v1.1 - Nagios Plugin\n";
  print "Copyright 2006 Jeroen Hoppenbrouwers <hoppie\@hoppie.nl>\n";
  print "More info: http://www.hoppie.nl/tempsens/\n";
  print "See source for License and Nagios config example.\n\n";
  print "Usage:\n";
  print " check_temperature -s <sensor> -t <target> -w <warn> -c <crit>\n\n";
  print "Options:\n";
  print " -s n             DigiTemp Sensor #, default 0\n";
  print " -t temperature   Target temperature in Centigrade, default 20\n";
  print " -w deviation     Temperature deviation from target to warn (required)\n";
  print " -c deviation     Temperature deviation from target when critical (required)\n\n";
  print "Output:\n";
  print " UNKNOWN/-1, OK/0, WARNING/1, CRITICAL/2\n";

  exit $exit_codes{'UNKNOWN'}; 
}