记得刚入职的时候，那时候什么都不懂，组长让我跑个迁移程序，还没跑完就关终端走人了，结果可想而知，那是第一次知道守护进程的概念。
当时后来是加了nohup参数解决的，
nohup ./program &
但是总是强迫别人用nohup来启动自己的程序毕竟不是办法，所以还是要把自己的进程变成守护进程才行。
C/C++的版本就不说了，这里有篇文章写的很清楚。
http://colding.bokee.com/5277082.html
这里主要介绍一下在网上无意发现的一个国外哥们的写的python版本：
http://www.jejik.com/articles/2007/02/a_simple_unix_linux_daemon_in_python/
顺便吐个槽，这哥们用的Vim配色明显是Wombat~~
代码如下(对私有函数名加了_前缀，便于理解，并加了一定的注释)：
#!/usr/bin/python# -*- coding: utf-8 -*-import sys, os, time, atexitfrom signal import SIGTERMclass 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): """ Restart the daemon """ self.stop() self.start() def _run(self): """ You should override this method when you subclass Daemon. It will be called after the process has been daemonized by start() or restart(). """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)
简单解释一下，整个类实现的功能：
1.进程脱离父进程及终端绑定
2.进程唯一性保证
3.标准输入/输出/错误重定向
附：
源代码下载
OK，就这样~
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