On a large Cisco Catalyst switch stack, almost all switchports are patched. I need to identify the ports, which are not in use, for connecting further devices.

Following switchports, cabling, patch fields and sockets to possible end devices is laborious and even then there could be temporarily used sockets. Looking at the activity of port LEDs is not reliable, since a user device can be shut off.

What's the easiest way to detect all unused switchports via IOS commands?