ethernet card question

[Rolando Abarca <rabarca@dcc.uchile.cl>]

is there a way to know if there's a cable connected to the ethernet 
card?... I ask this because I have a lombard powerbook, with a dhcp 
configured eth0, but if I boot GNU/Linux (ubuntu hoary) it stops waiting 
for a dhcp server, I would like to modify the networking script, so if 
there's no cable present on the card, don't configure the eth0 device, 
only the loopback. Is it possible? Something like OS X does when it's 
booting.
thanks a lot,

--
Rolando Abarca M. [rabarca.arroba@dcc.punto.uchile.punto.cl]
 "Tam pro papa quam pro rege bibunt omnes sine lege."