jamiesun · July 12, 2012 10:20 · Jul 14, 2012 · Jul 12, 2012
diff --git a/daemon.py b/daemon.py
@@ -0,0 +1,162 @@
+#! /usr/bin/env python2.7
+#encoding:utf-8
+#@description:一个python守护进程的例子
+#@tags:python,daemon
+import sys
+import os
+import time
+import 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
+        """
+        try: 
+            pid = os.fork() 
+            if pid > 0:
+                # exit first parent
+                sys.exit(0) 
+        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.setsid() 
+        os.umask(0) 
+
+        # do second fork
+        try: 
+            pid = os.fork() 
+            if pid > 0:
+                # exit from second parent
+                sys.exit(0) 
+        except OSError, e: 
+            sys.stderr.write("fork #2 failed: %d (%s)\n" % (e.errno, e.strerror))
+            sys.exit(1) 
+
+        # redirect standard file descriptors
+        sys.stdout.flush()
+        sys.stderr.flush()
+        si = file(self.stdin, 'r')
+        so = file(self.stdout, 'a+')
+        se = file(self.stderr, 'a+', 0)
+        os.dup2(si.fileno(), sys.stdin.fileno())
+        os.dup2(so.fileno(), sys.stdout.fileno())
+        os.dup2(se.fileno(), sys.stderr.fileno())
+
+        # write pidfile
+        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(60)
+            print 'daemon runing'
+
+
+
+
+if __name__ == "__main__":
+    daemon = MyDaemon("/var/run/demodaemon.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)
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