python 创建守护进程

#!/usr/bin/python
# -*- coding: gbk -*-
import sys,os,time
import sys, os, time, atexit
from signal import SIGTERM
class Daemon:
"""
A generic daemon class.
Usage: subclass the Daemon class and override the _run() method
"""
def __init__(self, pidfile, stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'):
self.stdin = stdin
self.stdout = stdout
self.stderr = stderr
self.pidfile = pidfile

def _daemonize(self):
"""
do the UNIX double-fork magic, see Stevens' "Advanced
Programming in the UNIX Environment" for details (ISBN 0201563177) http://www.erlenstar.demon.co.uk/unix/faq_2.html#SEC16 """
#脱离父进程
try:
pid = os.fork()
if pid > 0:
sys.exit(0)
except OSError, e:
sys.stderr.write("fork #1 failed: %d (%s)/n" % (e.errno, e.strerror))
sys.exit(1)

#脱离终端
os.setsid()
#修改当前工作目录
os.chdir("/")
#重设文件创建权限
os.umask(0)

#第二次fork，禁止进程重新打开控制终端
try:
pid = os.fork()
if pid > 0:
sys.exit(0)
except OSError, e:
sys.stderr.write("fork #2 failed: %d (%s)/n" % (e.errno, e.strerror))
sys.exit(1)

sys.stdout.flush()
sys.stderr.flush()
si = file(self.stdin, 'r')
so = file(self.stdout, 'a+')
se = file(self.stderr, 'a+', 0)
#重定向标准输入/输出/错误
os.dup2(si.fileno(), sys.stdin.fileno())
os.dup2(so.fileno(), sys.stdout.fileno())
os.dup2(se.fileno(), sys.stderr.fileno())

#注册程序退出时的函数，即删掉pid文件
atexit.register(self.delpid)
pid = str(os.getpid())
file(self.pidfile,'w+').write("%s/n" % pid)

def delpid(self):
os.remove(self.pidfile)
def start(self):
"""
Start the daemon
"""
# Check for a pidfile to see if the daemon already runs
try:
pf = file(self.pidfile,'r')
pid = int(pf.read().strip())
pf.close()
except IOError:
pid = None

if pid:
message = "pidfile %s already exist. Daemon already running?/n"
sys.stderr.write(message % self.pidfile)
sys.exit(1)

# Start the daemon
self._daemonize()
self._run()
def stop(self):
"""
Stop the daemon
"""
# Get the pid from the pidfile
try:
pf = file(self.pidfile,'r')
pid = int(pf.read().strip())
pf.close()
except IOError:
pid = None

if not pid:
message = "pidfile %s does not exist. Daemon not running?/n"
sys.stderr.write(message % self.pidfile)
return # not an error in a restart
# Try killing the daemon process
try:
while 1:
os.kill(pid, SIGTERM)
time.sleep(0.1)
except OSError, err:
err = str(err)
if err.find("No such process") > 0:
if os.path.exists(self.pidfile):
os.remove(self.pidfile)
else:
print str(err)
sys.exit(1)
def restart(self):
"""
重新启动 the daemon
"""
self.stop()
self.start()
def _run(self):
"""
你可以继承覆盖这个方法到你的类．
You should override this method when you subclass Daemon. It will be called after the process has been
daemonized by start() or restart().
"""

#继承Daemon
class MyDaemon(Daemon):
def _run(self):
while True:
time.sleep(1)

if __name__ == "__main__":
daemon = MyDaemon('/tmp/daemon-example.pid')
if len(sys.argv) == 2:
if 'start' == sys.argv[1]:
daemon.start()
elif 'stop' == sys.argv[1]:
daemon.stop()
elif 'restart' == sys.argv[1]:
daemon.restart()
else:
print "Unknown command"
sys.exit(2)
sys.exit(0)
else:
print "usage: %s start|stop|restart" % sys.argv[0]
sys.exit(2)