ffi_inotify.py

#!/usr/bin/env python
import signal
import ctypes
import sys
import ctypes.util
import os
from ctypes import (
    cast,
    c_int,
    c_int32,
    c_uint32,
    c_char_p
)
libc_name = ctypes.util.find_library('c')
libc = ctypes.CDLL(libc_name)
inotify_init = libc.inotify_init
inotify_init.argtypes = []
inotify_init.restype = c_int

inotify_rm_watch = libc.inotify_rm_watch
inotify_rm_watch.argtypes = [c_int, c_int]
inotify_rm_watch.restype = c_int

inotify_add_watch = libc.inotify_add_watch
inotify_add_watch.argtypes = [c_int, c_char_p, c_uint32]
inotify_add_watch.restype = c_int


FOREVER = True


def signal_handler(signal, frame):
    global FOREVER
    print "exit"
    FOREVER = False


signal.signal(signal.SIGINT, signal_handler)


class InotifyEvent(ctypes.Structure):
    _fields_ = [
        ("wd", c_int),
        ("mask", c_int32),
        ("cookie", c_int32),
        ("len", c_int32),
    ]

    @classmethod
    def decode(cls, buffer):
        event = cast(buffer, ctypes.POINTER(cls))[0]
        event.name = buffer[EVENT_SIZE: EVENT_SIZE + event.len]
        event.total_len = EVENT_SIZE + event.len
        return event

IN_CREATE = 0x00000100
IN_DELETE = 0x00000200
IN_ISDIR = 0x40000000
EVENT_SIZE = ctypes.sizeof(InotifyEvent)
EVENT_BUF_LEN = 1024 * (EVENT_SIZE + 16)

PATH = sys.argv[1] if len(sys.argv) == 2 else '/tmp'
i = 0
fd = inotify_init()
if fd < 0:
    raise Exception("inotify_init")

wd = inotify_add_watch(fd, PATH, IN_CREATE | IN_DELETE)

while FOREVER:
    buffer = os.read(fd, EVENT_BUF_LEN)
    buffer = ctypes.create_string_buffer(buffer)
    while buffer:
        event = InotifyEvent.decode(buffer)
        if event.len:
            if event.mask & IN_CREATE:
                if event.mask & IN_ISDIR:
                    print "New directory %s/%s created" % (PATH, event.name)
                else:
                    print "New file %s/%s created" % (PATH, event.name)
            elif event.mask & IN_DELETE:
                if event.mask & IN_ISDIR:
                    print "Directory %s/%s deleted" % (PATH, event.name)
                else:
                    print "File %s/%s deleted" % (PATH, event.name)
        buffer = buffer[event.total_len:]
inotify_rm_watch(fd, wd)
os.close(fd)