martinsoft/wifi-auto-reconnect

A simple script intended for use on Mac OS devices connected to a network with wifi only. The script periodically checks whether an IP address (ideally a router) is reachable. If unreachable, the script switches the device's wifi off and back on again - which causes the Mac to attempt to reconnect to the last used network. This is useful for headless Macs which might drop off of a network if, for example, the wifi router is restarted.

ShellMIT