denon_x311_volume

#!/usr/bin/gawk -f
# Denon x311 volume-plugin for munin
# Copyright (C) 2010 Kristian Lyngstøl
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

# This plugin asks a Denon (?) receiver over "telnet" what volume it's
# running at and parses the result. It's tested with Denon AVR 4311, but I
# suppose it works with the 3311 too, possibly more. It uses 192.168.0.60
# by default - because I'm lazy.

### Magic markers
# #%# family=manual
# #%# capabilities=
#
# Even if we _could_ do autoconf on ENVIRON["ip"], it's hazardous as you
# have little control over timeouts and risk hanging around annoying the
# user.

BEGIN {
	if (ARGV[1] == "config") {
		print "graph_title Denon AVR-4311 Volume"
		print "graph_category radio"
		print "volume.label Volume"
		print "volume.type GAUGE"
		exit 0
	}
	if (ENVIRON["ip"] == "") {
		ip="denon.kristian.int"
	} else {
		ip=ENVIRON["ip"]
	}
	Service="/inet/tcp/0/" ip "/23"

	# The AVR-4311 uses just a \r as line/record separator (annoying as
	# heck).
	RS="\r"

	# MV? asks for volume. Returned in MVXXZ - the z is optional
	print "MV?\r" |&Service
	Service |& getline
	close(Service)
	gsub("^MV","")

	# 445 == 44.5. 44 = 44. So only divide by ten if more than 2
	# characters were returned. Note that it also returns 005 for 0.5
	if (length >2) {
		n=$0/10
	} else {
		n=$0
	}

	# 99 is "0" and 99.5 is "0.5" (somewhat audible). I shift
	# everything by 1 because I prefer my lists to start at 0, not
	# -1....
	if (n==99 || n == 99.5) {
		n-=99
	} else {
		n+=1
	}
	printf "volume.value %0.1f\n",n
}