#!/usr/bin/env python
import sys, os
''' Module to fork the current process as a daemon.
    NOTE: don't do any of this if your daemon gets started by inetd!  inetd
    does all you need, including redirecting standard file descriptors;
    the chdir( ) and umask( ) steps are the only ones you may still want.
'''
def daemonize (stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'):
    ''' Fork the current process as a daemon, redirecting standard file
        descriptors (by default, redirects them to /dev/null).
    '''
    # Perform 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( )
    # Perform 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)
    # The process is now daemonized, redirect standard file descriptors.
    for f in sys.stdout, sys.stderr: f.flush( )
    si = file(stdin, 'r')
    so = file(stdout, 'a+')
    se = file(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 _example_main ( ):
    ''' Example main function: print a count & timestamp each 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 True:
        sys.stdout.write('%d: %s\n' % (c, time.ctime( )))
        sys.stdout.flush( )
        c = c + 1
        time.sleep(1)
if __name__ == "__main__":
    daemonize('/dev/null','/tmp/daemon.log','/tmp/daemon.log')
    _example_main( )