Well this little script and lauchd agent will auto-disable AirPort on active ethernet. It even notifies you using Growl, if installed.
Take this script and save it to /Library/Scripts/toggleAirport.sh. Go to that directory in Terminal and chmod the script (chmod 755 toggleAirport.sh will do) to be sure it's executable.
#!/bin/bash
function set_airport {
new_status=$1
if [ $new_status = "On" ]; then
/usr/sbin/networksetup -setairportpower en1 on
touch /var/tmp/prev_air_on
else
/usr/sbin/networksetup -setairportpower en1 off
if [ -f "/var/tmp/prev_air_on" ]; then
rm /var/tmp/prev_air_on
fi
fi
}
function growl {
# Checks whether Growl is installed
if [ -f "/usr/local/bin/growlnotify" ]; then
/usr/local/bin/growlnotify -m "$1" -a "AirPort Utility.app"
fi
}
# Set default values
prev_eth_status="Off"
prev_air_status="Off"
eth_status="Off"
# Determine previous ethernet status
# If file prev_eth_on exists, ethernet was active last time we checked
if [ -f "/var/tmp/prev_eth_on" ]; then
prev_eth_status="On"
fi
# Determine same for AirPort status
# File is prev_air_on
if [ -f "/var/tmp/prev_air_on" ]; then
prev_air_status="On"
fi
# Check actual current ethernet status
if [ "`ifconfig en0 | grep \"status: active\"`" != "" ]; then
eth_status="On"
fi
# And actual current AirPort status
air_status=`/usr/sbin/networksetup -getairportpower en1 | awk '{ print $4 }'`
# If any change has occured. Run external script (if it exists)
if [ "$prev_air_status" != "$air_status" ] || [ "$prev_eth_status" != "$eth_status" ]; then
if [ -f "./statusChanged.sh" ]; then
"./statusChanged.sh" "$eth_status" "$air_status" &
fi
fi
# Determine whether ethernet status changed
if [ "$prev_eth_status" != "$eth_status" ]; then
if [ "$eth_status" = "On" ]; then
set_airport "Off"
growl "Wired network detected. Turning AirPort off."
else
set_airport "On"
growl "No wired network detected. Turning AirPort on."
fi
# If ethernet did not change
else
# Check whether AirPort status changed
# If so it was done manually by user
if [ "$prev_air_status" != "$air_status" ]; then
set_airport $air_status
if [ "$air_status" = "On" ]; then
growl "AirPort manually turned on."
else
growl "AirPort manually turned off."
fi
fi
fi
# Update ethernet status
if [ "$eth_status" == "On" ]; then
touch /var/tmp/prev_eth_on
else
if [ -f "/var/tmp/prev_eth_on" ]; then
rm /var/tmp/prev_eth_on
fi
fi
exit 0
/System/Library/LaunchAgents/com.mine.toggleairport.plist
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0"> <dict> <key>Label</key> <string>com.asb.toggleairport</string> <key>OnDemand</key> <true/> <key>ProgramArguments</key> <array> <string>/Library/Scripts/toggleAirport.sh</string> </array> <key>WatchPaths</key> <array> <string>/Library/Preferences/SystemConfiguration</string> </array> </dict> </plist>
PS. It is also state aware. So if you turn your AirPort subsequently after plugging in a cable, it will not automatically turn it off again.
[crarko adds: I haven't tested this one. I put up the script and plist file here in a zipped folder for download.]

