Python中用MacFSEvents模块监视MacOS文件系统改变一例

最近一个项目中用gulp-watch不能满足需求，于是想到了用Python来解决问题。在安装了MacFSEvents模块后，写了下面一个小程序。

#!/usr/bin/env python2
#-*- coding: utf-8 -*-

import os,sys,signal
from   fsevents import Observer
from   fsevents import Stream  

def callback(FileEvent):
    # attributes of FileEvent：mask, cookie and name.
    # mask: 512-delete;256-create;2-changed
    if FileEvent.name.endswith("index.html") and FileEvent.mask == 256:
        print "site rebuild. redeploy extra assets"
        os.system("gulp")
    elif FileEvent.name.endswith(".scss") and FileEvent.mask == 2:
        print "scss changed! compile and redeploy extra assets"
        os.system("gulp sass")

if __name__ == '__main__':
    observer  = Observer()
    stream    = Stream(callback, ".", file_events=True)
    observer.schedule(stream)
    observer.start()
    #按Control+\强制结束

但是运行时发现只能用Control+\强杀进程，而不能用Control+C结束。

经google搜索及自行研究结果，得到下面这段程序。用fork子进程的方法，使得进程响应Control+C 退出。

 #!/usr/bin/env python2
 #-*- coding: utf-8 -*-

 import os,sys,signal
 from   fsevents import Observer
 from   fsevents import Stream  

 def callback(FileEvent):
     # attributes of FileEvent：mask, cookie and name.
     # mask: 512-delete;256-create;2-changed;...
     if FileEvent.name.endswith("index.html") and FileEvent.mask == 256:
         print "site rebuild. redeploy extra assets"
         os.system("gulp")
     elif FileEvent.name.endswith(".scss") and FileEvent.mask == 2:
         print "scss changed! compile and redeploy extra assets"
         os.system("gulp sass")

 def child():
     observer  = Observer()
     stream    = Stream(callback, ".", file_events=True)
     observer.schedule(stream)
     observer.start()

 class Watcher:
     """ 
　　　　　　创建一个做苦工的子进程。然后父进程等待KeyboardInterrupt并杀掉子进程。
27          
     """  

     def __init__(self):
         self.child = os.fork()
         if self.child == 0:
             child()
         else:
             self.watch()  

     def watch(self):
         try:
             os.wait()
         except KeyboardInterrupt:
             #捕获 Control+C，杀掉子进程
             print 'KEYBOARDINTERRUPT\n'
             self.kill()
         sys.exit()  

     def kill(self):
         try:
             os.kill(self.child, signal.SIGKILL)
         except OSError: pass  

 if __name__ == '__main__':
     Watcher()