Daemonize Python
From Noah.org
This short module shows the correct way to create a UNIX daemon process in Python. Creating a proper UNIX daemon is not as trivial as it sounds.
Click here to download: daemonize.py
#!/usr/bin/env python import sys, os '''This module is used to fork the current process into a daemon. Almost none of this is necessary (or advisable) if your daemon is being started by inetd. In that case, stdin, stdout and stderr are all set up for you to refer to the network connection, and the fork()s and session manipulation should not be done (to avoid confusing inetd). Only the chdir() and umask() steps remain useful. References: UNIX Programming FAQ 1.7 How do I get my program to act like a daemon? http://www.unixguide.net/unix/programming/1.7.shtml http://www.faqs.org/faqs/unix-faq/programmer/faq/ Advanced Programming in the Unix Environment W. Richard Stevens, 1992, Addison-Wesley, ISBN 0-201-56317-7. $Id: daemonize.py 251 2008-05-05 21:51:11Z noah $ ''' def daemonize (stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'): '''This forks the current process into a daemon. The stdin, stdout, and stderr arguments are file names that will be opened and be used to replace the standard file descriptors in sys.stdin, sys.stdout, and sys.stderr. These arguments are optional and default to /dev/null. Note that stderr is opened unbuffered, so if it shares a file with stdout then interleaved output may not appear in the order that you expect. ''' # Do first fork. try: pid = os.fork() if pid > 0: sys.exit(0) # Exit first parent. except OSError, e: sys.stderr.write ("fork #1 failed: (%d) %s\n" % (e.errno, e.strerror) ) sys.exit(1) # Decouple from parent environment. os.chdir("/") os.umask(0) os.setsid() # Do second fork. try: pid = os.fork() if pid > 0: sys.exit(0) # Exit second parent. except OSError, e: sys.stderr.write ("fork #2 failed: (%d) %s\n" % (e.errno, e.strerror) ) sys.exit(1) # Now I am a daemon! # Redirect standard file descriptors. si = open(stdin, 'r') so = open(stdout, 'a+') se = open(stderr, 'a+', 0) os.dup2(si.fileno(), sys.stdin.fileno()) os.dup2(so.fileno(), sys.stdout.fileno()) os.dup2(se.fileno(), sys.stderr.fileno()) def main (): '''This is an example main function run by the daemon. This prints a count and timestamp once per second. ''' import time sys.stdout.write ('Daemon started with pid %d\n' % os.getpid() ) sys.stdout.write ('Daemon stdout output\n') sys.stderr.write ('Daemon stderr output\n') c = 0 while 1: sys.stdout.write ('%d: %s\n' % (c, time.ctime(time.time())) ) sys.stdout.flush() c = c + 1 time.sleep(1) if __name__ == "__main__": daemonize('/dev/null','/tmp/daemon.log','/tmp/daemon.log') main()