Detect File Change Without Polling [duplicate]

Solution 1:

watchdog

Excellent cross platform library for watching directories.

From the website

Supported Platforms

• Linux 2.6 (inotify)

• Mac OS X (FSEvents, kqueue)

• FreeBSD/BSD (kqueue)

• Windows (ReadDirectoryChangesW with I/O completion ports; ReadDirectoryChangesW worker threads)

• OS-independent (polling the disk for directory snapshots and comparing them periodically; slow and not recommended)

I've used it on a couple projects and it seems to work wonderfully.

Solution 2:

For linux, there is pyinotify.

From the homepage:

Pyinotify is a Python module for monitoring filesystems changes. Pyinotify relies on a Linux Kernel feature (merged in kernel 2.6.13) called inotify. inotify is an event-driven notifier, its notifications are exported from kernel space to user space through three system calls. pyinotify binds these system calls and provides an implementation on top of them offering a generic and abstract way to manipulate those functionalities.

Thus it is obviously not cross-platform and relies on a new enough kernel version. However, as far as I can see, requiring kernel support would be true about any non-polling mechanism.