Question

I want to parse a file everytime a new file is created in a certain directory. For this, I’m trying to use pyinotify to setup a directory to watch for IN_CREATE kernel events, and fire the parse() method.

Here is the module:

from pyinotify import WatchManager,
    ThreadedNotifier, ProcessEvent, IN_CREATE

class Watcher(ProcessEvent):

    watchdir = '/tmp/watch'

    def __init__(self):
        ProcessEvent.__init__(self)
        wm = WatchManager()
        self.notifier = ThreadedNotifier(wm, self)
        wdd = wm.add_watch(self.watchdir, IN_CREATE)
        self.notifier.start()

    def process_IN_CREATE(self, event):
        pfile = self._parse(event.pathname)
        print(pfile)

    def _parse(self, filename):
        f = open(filename)
        file = [line.strip() for line in f.readlines()]
        f.close()
        return file

if __name__ == '__main__':
    Watcher()

The problem is that the list returned by _parse is empty when triggered by a new file creation event, like so (the file is created in another window while watcher.py is running):

$ python watcher.py
[]

…but strangely enough, it works from an interpreter session when called directly.

>>> import watcher
>>> w = watcher.Watcher()
>>> w._parse('/tmp/watch/sample')
['This is a sample file', 'Another line', 'And another...']

Why is this happening? The farthest I’ve come debugging this thing is to know that something is making pyinotify not read the file correctly. But… why?

Answer 1

may be you want to wait till file is closed?