Hi,
I'd like to know if there is a way to know whether the cable is connected
to my interface. The aim is to detect it at startup so as to know if I need
eth0 set up or not (on a laptop), in which case (if not needed) only the
wifi card is set up.

In fact the problem is that if the wifi card AND the eth0 interface are
both set up, I cannot use the wifi card, even if the cable is not plugged
to the eth0 interface.

My route says that the default gw is wlan0, but eth0 is set first.
Any idea ?