How to prevent Python script from Force exit?

Question

I am running a python script and trying to prevent from force exiting or print an error message or log that into the log file.

I am already using logging.info("") for logging.. or just print for printing something..

but what or how do I create a method or function that can either do print or log when it force exit?

For example, if my test.py is running and I press Ctrl + C to exit out.. I want to log that or print out..

signal.signal(signal.SIGUSR1, handler)
logging.info("Checked for signal to stop")
if stop:
        logging.info("Inside of main if loop for stop signal")
        logging.info("Stop signal captured. Exiting the program")
        smtpObj.sendmail(sender, receivers, message + "Stop signal captured. Exiting the program")
        sys.exit("EXIT SIGNAL CAPTURED: EXITING")

I am using above coding for logging for when I want to exit the program. But this doesn't deal with something like ctrl + c I want to also log just in case program exit by accident or something

Are you wanting to log other exits, or just when ctrl + c is used? — lsowen
– lsowen, Commented Apr 8, 2015 at 19:31
You want to read about python exception handling. docs.python.org/3/tutorial/errors.html — Codie CodeMonkey
– Codie CodeMonkey, Commented Apr 8, 2015 at 19:32
It would be more helpful if you told us why your code is "force exiting" — notorious.no
– notorious.no, Commented Apr 8, 2015 at 19:42
Take a look to atexit too docs.python.org/2/library/atexit.html — Jaime Soriano
– Jaime Soriano, Commented Apr 8, 2015 at 21:24

notorious.no · Accepted Answer · 2015-04-08 21:35:31Z

2

UPDATED

Use try and except:

try:
    signal.signal(signal.SIGUSR1, handler)
    logging.info("Checked for signal to stop")
    if stop:
        logging.info("Inside of main if loop for stop signal")
        logging.info("Stop signal captured. Exiting the program")
        smtpObj.sendmail(sender, receivers, message + "Stop signal captured.     Exiting the program")
        sys.exit("EXIT SIGNAL CAPTURED: EXITING")
except KeyboardInterrupt as kbe:
    log.info(str(kbe))

You could also leverage the atexit module to execute a function when the script exits.

import atexit

def alldone():
    log.warning('Something went wrong')

# your code here...

https://docs.python.org/2/library/atexit.html

edited Apr 8, 2015 at 21:35

answered Apr 8, 2015 at 19:32

notorious.no

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RVT · Accepted Answer · 2015-04-08 19:53:22Z

0

You should likely take a look at Python Signal Handlers (specifically signal.CTRL_C_EVENT).

Here is a more-complete answer... NOTE: You can make your processes fairly unkillable by using such things.

#!/usr/bin/env python

import signal, os
import time

def handler( signum, frame ):
  print "Signal handler caught", signum, "@", time.ctime()
  if signum == 2:
    raise "Caught Signal 2 - Exiting"

#
# Windows Supported Values
#
#signal.signal( signal.SIGABRT, handler )
#signal.signal( signal.SIGFPE, handler )
#signal.signal( signal.SIGILL, handler )
#signal.signal( signal.SIGINT, handler )
#signal.signal( signal.SIGSEGV, handler )
#signal.signal( signal.SIGTERM, handler )

#
# UNIX Supported Values (YMMV)
#
signal.signal( signal.SIGABRT, handler )
signal.signal( signal.SIGALRM, handler )
signal.signal( signal.SIGBUS, handler )
signal.signal( signal.SIGCHLD, handler )
signal.signal( signal.SIGCLD, handler )
signal.signal( signal.SIGCONT, handler )
signal.signal( signal.SIGFPE, handler )
signal.signal( signal.SIGHUP, handler )
signal.signal( signal.SIGILL, handler )
signal.signal( signal.SIGINT, handler )
signal.signal( signal.SIGIO, handler )
signal.signal( signal.SIGIOT, handler )
#signal.signal( signal.SIGKILL, handler )
signal.signal( signal.SIGPIPE, handler )
signal.signal( signal.SIGPOLL, handler )
signal.signal( signal.SIGPROF, handler )
signal.signal( signal.SIGPWR, handler )
signal.signal( signal.SIGQUIT, handler )
signal.signal( signal.SIGRTMAX, handler )
signal.signal( signal.SIGRTMIN, handler )
signal.signal( signal.SIGSEGV, handler )
#signal.signal( signal.SIGSTOP, handler )
signal.signal( signal.SIGSYS, handler )
signal.signal( signal.SIGTERM, handler )
signal.signal( signal.SIGTRAP, handler )
signal.signal( signal.SIGTSTP, handler )
signal.signal( signal.SIGTTIN, handler )
signal.signal( signal.SIGTTOU, handler )
signal.signal( signal.SIGURG, handler )
signal.signal( signal.SIGUSR1, handler )
signal.signal( signal.SIGUSR2, handler )
signal.signal( signal.SIGVTALRM, handler )
signal.signal( signal.SIGWINCH, handler )
signal.signal( signal.SIGXCPU, handler )
signal.signal( signal.SIGXFSZ, handler )
#signal.signal( signal.SIG_DFL, handler )
signal.signal( signal.SIG_IGN, handler )


print time.ctime(), " - Started"

while True:
  time.sleep( 1 )
  print " Tick:", time.ctime()

edited Apr 8, 2015 at 19:53

answered Apr 8, 2015 at 19:32

RVT

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2 Comments

Tim Over a year ago

I edited the question. I was using something similar but does this catch all exiting? such as ctrl + c ?

RVT Over a year ago

You should try running the script and test to see what happens when you send different signals... it's just an indefinite loop that prints the time once a second - and calls the handler for pretty much any signal it receives. In the case of UN*X, for example, a CTRL-C sends signal 2 (signal.SIGINT). In the case of your rephrased question, you likely just want to set SIGINT to be handled by a function like "stop" (which should be a def, not an if, which accepts two arguments).

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