# linux 下应该是类似这样
import signal, os

def handler(signum, frame):
print 'Signal handler called with signal', signum
raise IOError, "Couldn't open device!"

# Set the signal handler and a 5-second alarm
signal.signal(signal.SIGALRM, handler)
signal.alarm(5)

# This open() may hang indefinitely
fd = os.open('/dev/ttyS0', os.O_RDWR)

signal.alarm(0) # Disable the alarm