Look for and connect to WiFi network.

mac-network-check.sh

#!/bin/bash

##  This script checks to see if the Mac is connected to
##  a particular network. If it isn't, the script shuts off
##  the wifi radio and turns it back on, then attempts
##  to connect to the specified network.
##
##  You can run this script at regular intervals with
##  an app called Lingon, which utilizes launchd.
##  Just make sure to chmod -x the script first.

network="YOUR_NETWORK_NAME"
password="YOUR_NETWORK_PASSWORD"
confirmStr="Current Wi-Fi Network: "$network
networkTest=`networksetup -getairportnetwork en1`

if [ "$networkTest" = "$confirmStr" ]
then
	echo "You are on the expected network"
else
	networksetup -setairportpower en1 off
	networksetup -setairportpower en1 on
	networksetup -setairportnetwork en1 $network $password
	echo `networksetup -getairportnetwork en1`
fi

I created this because I'm having issues with a laptop driving a public display on a flaky WiFi network. I don't have control over the flaky WiFi and I don't have easy access to the building to deal with issues that can't be solived via remote access (like, say, flaky WiFi).

I plan to set the laptop to automatically sleep at regular intervals and when it wakes up, I'd like for it to check it's internet connection.