Automatically disable Wifi when an Ethernet connection (cable) is plugged in on a Mac.

com.krispayne.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.krispayne.toggleairport</string>
  <key>KeepAlive</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>

toggleAirport.sh

#!/bin/bash

function set_airport() {
    new_status=$1
    if [ "${new_status}" = "On" ]; then
        /usr/sbin/networksetup -setairportpower "${air_name}" on
        touch /var/tmp/prev_air_on
    else
        /usr/sbin/networksetup -setairportpower "${air_name}" 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 "${1}" -a "AirPort Utility.app"
    else
        osascript -e "display notification \"${1}\" with title \"Wifi Toggle\" "
    fi
}

# Set default values
prev_eth_status="Off"
prev_air_status="Off"
eth_status="Off"

# Grab the names of the adapters. We assume here that any ethernet connection name contains "Ethernet"
# Also assume that wireless devices contain Wi-Fi or AirPort
eth_names=$(/usr/sbin/networksetup -listnetworkserviceorder | sed -En 's|^\(Hardware Port: .*Ethernet.*, Device: (en.)\)$|\1|p')
air_name=$(/usr/sbin/networksetup -listnetworkserviceorder | sed -En 's/^\(Hardware Port: (.*Wi-Fi.*|.*AirPort.*), Device: (en.)\)$/\2/p')

# 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 previous AirPort status
# If file prev_air_on exists, AirPort was active last time we checked
if [ -f "/var/tmp/prev_air_on" ]; then
    prev_air_status="On"
fi

# Check actual current ethernet status
for eth_name in ${eth_names}; do
    if ([ "${eth_name}" != "" ] && [ "$(ifconfig "${eth_name}" | grep "status: active")" != "" ]); then
        eth_status="On"
    fi
done

# And actual current AirPort status
air_status=$(/usr/sbin/networksetup -getairportpower "${air_name}" | 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

ToggleWiFi.md

Overview

This is a bash script that will automatically turn your wifi off if you connect your computer to an ethernet connection and turn wifi back on when you unplug your ethernet cable/adapter. If you decide to turn wifi on for whatever reason, it will remember that choice. This was improvised from this mac hint to work with Yosemite, and without hard-coding the adapter names. It's supposed to support growl, but I didn't check that part. I did, however, add OSX notification center support. Feel free to fork and fix any issues you encounter.

Most the credit for these changes go to Dave Holland and Albert Bori

Requirements

• Mac OSX 10+
• Administrator privileges

Installation Instructions

• Copy toggleAirport.sh to /Library/Scripts/
• Run chmod 755 /Library/Scripts/toggleAirport.sh
• Copy com.krispayne.toggleairport.plist to /Library/LaunchAgents/
• Run chmod 600 /Library/LaunchAgents/com.krispayne.toggleairport.plist
• Run sudo launchctl load /Library/LaunchAgents/com.krispayne.toggleairport.plist to start the watcher

Uninstall Instructions

• Run sudo launchctl unload /Library/LaunchAgents/com.krispayne.toggleairport.plist to stop the watcher
• Delete /Library/Scripts/toggleAirport.sh
• Delete /Library/LaunchAgents/com.krispayne.toggleairport.plist
• Delete /private/var/tmp/prev_eth_on
• Delete /private/var/tmp/prev_air_on

Misc

To debug, just run: sudo /Library/Scripts/toggleAirport.sh and add echo's wherever you'd like