knut0815 / inotify_simple

A simple Python wrapper around inotify. No fancy bells and whistles, just a literal wrapper with ctypes.

inotify_simple 1.1

inotify_simple is a simple Python wrapper around inotify. No fancy bells and whistles, just a literal wrapper with ctypes. Only 122 lines of code!

inotify_init() is wrapped as a class that does little more than hold the resulting inotify file descriptor. A read() method is provided which reads available data from the file descriptor and returns events as namedtuple objects after unpacking them with the struct module. inotify_add_watch() and inotify_rm_watch() are wrapped with no changes at all, taking and returning watch descriptor integers that calling code is expected to keep track of itself, just as one would use inotify from C. Works with Python 2.7 or Python >= 3.2.

View on PyPI | Fork me on github | Read the docs

Installation

to install inotify_simple, run:

$ pip3 install inotify_simple

or to install from source:

$ python3 setup.py install

Note: If on Python < 3.4, you'll need the backported enum34 module.

inotify_simple is a small amount of code and unlikely to change much in the future until inotify itself or Python changes, so you can also just copy and paste it into your project to avoid the extra dependency with pretty low risk.

Introduction

There are many inotify python wrappers out there. I found them all unsatisfactory. Most are far too high-level for my tastes, and the supposed convenience they provide actually limits one from using inotify in ways other than those the author imagined. Others are C extensions, requiring compilation for different platforms and Python versions, rather than a pure python module using ctypes. This one is pretty low-level and really just does what inotify itself does and nothing more. So hopefully if I've written it right, it will remain functional well into the future with no changes, recompilation or attention on my part.

Example usage

import os
from inotify_simple import INotify, flags

os.mkdir('/tmp/inotify_test')

inotify = INotify()
watch_flags = flags.CREATE | flags.DELETE | flags.MODIFY | flags.DELETE_SELF
wd = inotify.add_watch('/tmp/inotify_test', watch_flags)

# Now create, delete and modify some files in the directory being monitored:
os.chdir('/tmp/inotify_test')
# CREATE event for a directory:
os.system('mkdir foo')
# CREATE event for a file:
os.system('echo hello > test.txt')
# MODIFY event for the file:
os.system('echo world >> test.txt')
# DELETE event for the file
os.system('rm test.txt')
# DELETE event for the directory
os.system('rmdir foo')
os.chdir('/tmp')
# DELETE_SELF on the original directory. # Also generates an IGNORED event
# indicating the watch was removed.
os.system('rmdir inotify_test')

# And see the corresponding events:
for event in inotify.read():
    print(event)
    for flag in flags.from_mask(event.mask):
        print('    ' + str(flag))

This outputs the following:

Event(wd=1, mask=1073742080, cookie=0, name=u'foo')
    flags.CREATE
    flags.ISDIR
Event(wd=1, mask=256, cookie=0, name=u'test.txt')
    flags.CREATE
Event(wd=1, mask=2, cookie=0, name=u'test.txt')
    flags.MODIFY
Event(wd=1, mask=512, cookie=0, name=u'test.txt')
    flags.DELETE
Event(wd=1, mask=1073742336, cookie=0, name=u'foo')
    flags.DELETE
    flags.ISDIR
Event(wd=1, mask=1024, cookie=0, name=u'')
    flags.DELETE_SELF
Event(wd=1, mask=32768, cookie=0, name=u'')
    flags.IGNORED

Note that the flags, since they are defined with an enum.IntEnum, print as what they are called rather than their integer values. However they are still just integers and so can be bitwise-ANDed and ORed etc with masks etc. The flags.from_mask() method bitwise-ANDs a mask with all possible flags and returns a list of matches. This is for convenience and useful for debugging which events are coming through, but performance critical code should generally bitwise-AND masks with flags of interest itself so as to not do unnecessary checks.

See here for more.