Inotify_add_watch usage notes

1. inotify_add_watch does not return an FD, but an identifier.
2. For the same path, inotify_add_watch returns the same identifier. You do not need to call close, but you need to call inotify_rm_watch to delete it.

Pay attention to this feature when reading, writing, and disabling monitoring files. However, inotify_init returns a real FD, so you need to call close to close it.
However, if the path is the same but the path is alternating by add and RM, it will not be repeated and will increase from 1.
Add_watch is performed on the same path before the previous one is RM. Actually, it is only modified and the return value will not change.

More attention: http://bbs.hadoopor.com/thread-1852-1-1.html