+
−import os
+
−import sys
+
−
+
−if os.name == 'posix':
+
−    def become_daemon(our_home_dir='.', out_log='/dev/null',
+
−                      err_log='/dev/null', umask=022):
+
−        "Robustly turn into a UNIX daemon, running in our_home_dir."
+
−        # First fork
+
−        try:
+
−            if os.fork() > 0:
+
−                sys.exit(0)     # kill off parent
+
−        except OSError, e:
+
−            sys.stderr.write("fork #1 failed: (%d) %s\n" % (e.errno, e.strerror))
+
−            sys.exit(1)
+
−        os.setsid()
+
−        os.chdir(our_home_dir)
+
−        os.umask(umask)
+
−
+
−        # Second fork
+
−        try:
+
−            if os.fork() > 0:
+
−                os._exit(0)
+
−        except OSError, e:
+
−            sys.stderr.write("fork #2 failed: (%d) %s\n" % (e.errno, e.strerror))
+
−            os._exit(1)
+
−
+
−        si = open('/dev/null', 'r')
+
−        so = open(out_log, 'a+', 0)
+
−        se = open(err_log, 'a+', 0)
+
−        os.dup2(si.fileno(), sys.stdin.fileno())
+
−        os.dup2(so.fileno(), sys.stdout.fileno())
+
−        os.dup2(se.fileno(), sys.stderr.fileno())
+
−        # Set custom file descriptors so that they get proper buffering.
+
−        sys.stdout, sys.stderr = so, se
+
−else:
+
−    def become_daemon(our_home_dir='.', out_log=None, err_log=None, umask=022):
+
−        """
+
−        If we're not running under a POSIX system, just simulate the daemon
+
−        mode by doing redirections and directory changing.
+
−        """
+
−        os.chdir(our_home_dir)
+
−        os.umask(umask)
+
−        sys.stdin.close()
+
−        sys.stdout.close()
+
−        sys.stderr.close()
+
−        if err_log:
+
−            sys.stderr = open(err_log, 'a', 0)
+
−        else:
+
−            sys.stderr = NullDevice()
+
−        if out_log:
+
−            sys.stdout = open(out_log, 'a', 0)
+
−        else:
+
−            sys.stdout = NullDevice()
+
−
+
−    class NullDevice:
+
−        "A writeable object that writes to nowhere -- like /dev/null."
+
−        def write(self, s):
+
−            pass