Join a wifi network from terminal or a shell script.

AIRPORT="en1"; #may be en0, use networksetup -listallhardwareports to check

WIFI_NETWORK_NAME="network-name"

WIFI_PASSWORD="password"

networksetup -setairportpower $AIRPORT off

networksetup -setairportpower $AIRPORT on

sleep 2

if networksetup -getairportnetwork $AIRPORT | grep -i -a $WIFI_NETWORK_NAME ;

then

    echo 'Connected!';

    exit 0

fi

if networksetup -setairportnetwork $AIRPORT $WIFI_NETWORK_NAME $WIFI_PASSWORD | grep -i -a "Failed" ;

then

    echo 'Failed to connect, just restarting...';

    networksetup -setairportpower $AIRPORT off

    networksetup -setairportpower $AIRPORT on

    sleep 1

fi

networksetup -getairportnetwork $AIRPORT

exit 0;