CODEWITHSUNDEEP
pythonlinuxsignals
user192082107
user192082107

Reputation: 1367

How can I send a signal from a python program?

I have this code which listens to USR1 signals

import signal
import os
import time

def receive_signal(signum, stack):
    print 'Received:', signum

signal.signal(signal.SIGUSR1, receive_signal)
signal.signal(signal.SIGUSR2, receive_signal)

print 'My PID is:', os.getpid()

while True:
    print 'Waiting...'
    time.sleep(3)

This works when I send signals with kill -USR1 pid

But how can I send the same signal from within the above python script so that after 10 seconds it automatically sends USR1 and also receives it , without me having to open two terminals to check it?

Upvotes: 39

Views: 77431

Answers (2)

moomima
moomima

Reputation: 1340

You can use os.kill():

os.kill(os.getpid(), signal.SIGUSR1)

Put this anywhere in your code that you want to send the signal from.

Upvotes: 69

Robᵩ
Robᵩ

Reputation: 168616

If you are willing to catch SIGALRM instead of SIGUSR1, try:

signal.alarm(10)

Otherwise, you'll need to start another thread:

import time, os, signal, threading
pid = os.getpid()
thread = threading.Thread(
  target=lambda: (
    time.sleep(10),
    os.kill(pid, signal.SIGUSR1)))
thread.start()

Thus, this program:

import signal
import os
import time

def receive_signal(signum, stack):
    print 'Received:', signum

signal.signal(signal.SIGUSR1, receive_signal)
signal.signal(signal.SIGUSR2, receive_signal)
signal.signal(signal.SIGALRM, receive_signal)  # <-- THIS LINE ADDED

print 'My PID is:', os.getpid()

signal.alarm(10)                               # <-- THIS LINE ADDED

while True:
    print 'Waiting...'
    time.sleep(3)

produces this output:

$ python /tmp/x.py 
My PID is: 3029
Waiting...
Waiting...
Waiting...
Waiting...
Received: 14
Waiting...
Waiting...

Upvotes: 6

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