OT: full/half duplex nic?

[Rob Tandy <rtandy-debian@slowchip.com>]

How does one tell if a network card is running at full or half duplex?

I looked at the bootup messages with dmesg and the information provided by
ifconfig, but no luck.

eth0      Link encap:Ethernet  HWaddr 00:50:BA:C6:22:40  
          inet addr:xxx.xxx.xxx.xxx Bcast:xxx.xxx.xxx.xxx Mask:xxx.xxx.xxx.xxx
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3910382 errors:0 dropped:0 overruns:0 frame:0
          TX packets:970288 errors:0 dropped:0 overruns:0 carrier:0
          collisions:148 txqueuelen:100 
          Interrupt:9 Base address:0xfc80

TIA,
rob