# Check wifi connection...
ping 192.168.178.1 -I wlan0 -c4 > /dev/null
# '$?' is the exit code of previous ping command
if [ $? != 0 ] #  => failure
then
  logger "No network connection, restarting wlan0 Now!"
  echo "No network connection, restarting wlan0"
  # Take WiFi down
  ip link set dev wlan0 down
  sleep 5
  # Take WiFi up
  ip link set dev wlan0 up
fi