CODEWITHSUNDEEP
pythonsignalsalarm
user1530405
user1530405

Reputation: 455

Periodic signal alarm

I would like a my Python script to receive a periodic alarm say every 5 seconds. I have tried the following code, but it only receive the alarm once then hangs.

import os
import signal
import time

def handler(signum, stack):
    print 'Alarm: ', time.ctime()

signal.signal(signal.SIGALRM, handler)
signal.alarm(5)

Upvotes: 1

Views: 7801

Answers (2)

Navin Maheshwari
Navin Maheshwari

Reputation: 1

Because alarm is set once only. If you need periodic
Try this:

def handler(signum, stack):
   print 'Alarm: ', time.ctime()
   signal.alarm(5)

Upvotes: 0

flaschbier
flaschbier

Reputation: 4177

Nothing hangs, nothing receives the alarm once. Your program is already dead when the alarm bell rings the first time. Try so:

import signal
import time

def handler(signum, stack):
    print 'Alarm: ', time.ctime()

signal.signal(signal.SIGALRM, handler)
signal.alarm(5)
time.sleep(10)
print "interrupted"

When you want it in a loop, just wrap it in a loop:

signal.signal(signal.SIGALRM, handler)
for i in range(1000):
    signal.alarm(5)
    time.sleep(10)
    print "interrupted #%d" % i

You can also do infinite loop. But catch KeyboardInterrupt in this case to avoid nasty exceptions like

Alarm:  Sat Mar 19 08:28:06 2016
interrupted #2
^CTraceback (most recent call last):
  File "alaam.py", line 10, in <module>
    time.sleep(10)
KeyboardInterrupt

Upvotes: 3

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