How can I receive notifications of filesystem changes in OS X?

Question

In Windows, I can use the FindNextChangeNotification API to watch a file or folder for changes. For example, I can watch a folder and get notified when a file is added or removed.

Is there a similar API on OS X?

Answer 1

Mac OS X v10.5 introduces the File System Events API. Have a look at:

• File System Events API Collection
• Technology Overview (archive)
• Using the File System Events API (archive)
• File System Events Programming Guide (PDF of 2008)

Answer 2

FSEvents is nice, but for watching just a small set of files or folders it's rather overkill, and it does require Leopard or newer. (The underlying technology was introduced in Tiger, but the API wasn't public.)

As a possible alternative, note that OS X inherits kqueue from FreeBSD (at least as of Panther). You can search for examples of EVFILT_VNODE usage, that's what you want to use to watch for file alterations.