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:  
    """ 
26　　　　　　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()