I am running Ubuntu 12.04.
Here is what I am trying to do:

I copied and adapted a shell script from here: http://yatse.leetzone.org/redmine/boards/2/topics/2088. It listens to UDP port 9 for Wake-On-LAN packages. When it receives a package, it should start xbmc. Here is the script /home/myusername/.xbmc/autostarter:

#!/bin/bash

UDP_PORT=9          # Change this if you need to run this on a different port



START_PHRASE="E.....@"    

START_PHRASE_ESCAPED="E.....@"    



# The following block checks if the user running this script has the required      privileges to listen on the port specified above

WHO=`whoami`

if [ "$WHO" != "root" ]; then

     echo "Cannot start unless running as root." >> /var/log/xbmc-starter.log

  exit 1

fi



echo "Listening on port $UDP_PORT for start command" >> /var/log/xbmc-starter.log



while [ true ]; do

     # Wait for a packet to come in

     LISTEN=`tcpdump "udp port $UDP_PORT" -A -c 1 2>&1 | grep -o    "$START_PHRASE_ESCAPED"`

     # Make sure that we received the right command

     if [ "$LISTEN" = "$START_PHRASE" ]; then

        echo "Starting XBMC" >> /var/log/xbmc-starter.log

        /usr/bin/xbmc 

        echo "test log after command" >> /var/log/xbmc-starter.log

     fi

     # Sleep, to be nice, for unwanted rogue processes writing to our port

     sleep 1

done

When I run this script from command line with sudo and send the WOL package, it works and starts xbmc.

sudo ./autostarter

The log output is:

Listening on port 9 for start command

Starting XBMC

test log after command

But when I run it from an upstart script, it creates the same log output but does not start xbmc. Here is my upstart script xbmc-starter.conf:

# Starts a listener that runs the xbmc start script when a WOL package is received

description     "start xbmc wol listener script"

# runlevels

start on runlevel [2345]

stop on runlevel [!2345]

exec /home/myusername/.xbmc/autostarter

And the log output:

Listening on port 9 for start command

Starting XBMC

test log after command

Why doesn't it start XBMC?