Python Signal processing module signal

Python Signal processing module signal

Python's module for signal processing mainly uses the signal module, but the signal is primarily for UNIX systems, so Python does not perform well on the Windows platform for signal processing.

To see the semaphore in Python, you can use DIR (signal) to view it.

Signal.signal ()

In the signal module, the main use of the signal.signal () function to preset the signal processing function

singnal.signal(signalnum, handler)

The first parameter is the semaphore, the second parameter signal processing function.

Let's look at a simple example where

• Defines a signal processing function, Signal_handler (), to handle the operation performed when the program receives a signal
• A loop waits for a signal to be sent

#!/usr/bin/env python#-*-Coding:utf-8-*-ImportSignalImportTime def signal_handler(Signum, frame):Print' Received signal: ', Signum) while True: Signal.signal (signal. SIGHUP, Signal_handler)# 1Signal.signal (signal. SIGINT, Signal_handler)# 2Signal.signal (signal. Sigquit, Signal_handler)# 3Signal.signal (signal. SIGALRM, Signal_handler)#Signal.signal (signal. SIGTERM, Signal_handler)#Signal.signal (signal. Sigcont, Signal_handler)#     while True: Print (' Waiting ') Time.sleep (1)

Run the above program

python test.py

Then open a different terminal, find the corresponding process, and perform the following kill operation

kill -1 <pid>kill -2 <pid>kill -3 <pid>kill -14 <pid>kill -15 <pid>kill -18 <pid>kill -9# 最后杀死进程

At this point, you can see the output of the test.py, printing is the specific received signal.

One thing to note here is that the SIGINT signal is registered in the program, so using CTRL + C after running the program does not end the process, but still the signal received by the printing process.

Signal.alarm ()

In addition, the signal module provides a useful function signal.alarm (), which is used to send a SIGALRM signal to the process itself after a certain amount of time, such as the following example setting to send itself a SIGALRM signal after 5 seconds.

#!/usr/bin/env python# -*- coding: utf-8 -*-import signalimport timedef signal_handler(signum, frame):    print(‘Received signal: ‘, signum)whileTrue:    # 14    signal.alarm(5)    whileTrue:        print(‘waiting‘)        time.sleep(1)

Reference

• Http://man7.org/linux/man-pages/man7/signal.7.html
• Https://docs.python.org/2/library/signal.html#module-signal

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Python Signal processing module signal