thanks Javalee
I use arping to get another pc nic's mac.
the following lines
ARPING 192.168.0.252 from 192.168.0.200 eth0
Unicast reply from 192.168.0.252 [00:40:63:CA:C89] 0.762ms
Sent 1 probes (1 broadcast(s))
Received 1 response(s)
but when i use your script i get the following result:
eth0 00:40:63:CA:C89 broadcast(s))