FSEvents API
Introduced in Mac OS X v10.5, the FSEvents API notifies your application when changes occur in the file system. You can use file system events to monitor directories for any changes, such as the creation, modification, or removal of contained files and directories. Although kqueues provide similar behavior, the FSEvents API provides a much simpler way to monitor many directories at once. For example, you can use file system events to monitor entire file system hierarchies rooted at a specific directory and still receive notifications about individual directories in the hierarchy. The implementation of file system events is lightweight and efficient, providing built-in coalescing when multiple changes occur within a short period of time to one or many directories.
The FSEvents API is not intended for detecting fine-grained changes to individual files. You would not use this to detect changes to an individual file as in a virus checker program. Instead, you might use FSEvents to detect general changes to a file hierarchy. For example, you might use this technology in backup software to detect what files changed. You might also use it to monitor a set of data files your application uses, but which can be modified by other applications as well.
For information on how to use the FSEvents API, see File System Events Programming Guide.
