Yurttas/PL/SL/python/docs/core-python-programming/doc/20/lib/Signal Example.html

[[yurttas/PL/SL/python/docs/core-python-programming/doc/20/lib/module-signal.html|]]

[[yurttas/PL/SL/python/docs/core-python-programming/doc/20/lib/module-socket.html|]]

Python Library Reference

[[yurttas/PL/SL/python/docs/core-python-programming/doc/20/lib/contents.html|]]

[[yurttas/PL/SL/python/docs/core-python-programming/doc/20/lib/modindex.html|]]

[[yurttas/PL/SL/python/docs/core-python-programming/doc/20/lib/genindex.html|]]

Previous: 7.1 signal Up: 7.1 signal Next: 7.2 socket

7.1.1 Example

Here is a minimal example program. It uses the alarm() function to limit the time spent waiting to open a file; this is useful if the file is for a serial device that may not be turned on, which would normally cause the os.open() to hang indefinitely. The solution is to set a 5-second alarm before opening the file; if the operation takes too long, the alarm signal will be sent, and the handler raises an exception.

import signal, os, FCNTL 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', FCNTL.O_RDWR) signal.alarm(0) # Disable the alarm