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#!/usr/bin/python
'''
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 as useful.
References:
UNIX Programming FAQ
1.7 How do I get my program to act like a daemon?
http://www.erlenstar.demon.co.uk/unix/faq_2.html#SEC16
Advanced Programming in the Unix Environment
W. Richard Stevens, 1992, Addison-Wesley, ISBN 0-201-56317-7.
History:
2001/07/10 by J�rgen Hermann
2002/08/28 by Noah Spurrier
2003/02/24 by Clark Evans
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66012
'''
import sys, os, time
from signal import SIGTERM
def daemonize(stdout='/dev/null', stderr=None, stdin='/dev/null', pidfile=None, startmsg=None):
'''
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)
# Open file descriptors and print start message
if not stderr: stderr = stdout
si = file(stdin, 'r')
so = file(stdout, 'a+')
se = file(stderr, 'a+', 0)
pid = str(os.getpid())
if startmsg:
sys.stderr.write("\n%s\n" % startmsg % pid)
sys.stderr.flush()
if pidfile: file(pidfile,'w+').write("%s\n" % pid)
# Redirect standard file descriptors.
os.dup2(si.fileno(), sys.stdin.fileno())
os.dup2(so.fileno(), sys.stdout.fileno())
os.dup2(se.fileno(), sys.stderr.fileno())
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