will NSFileSystemFileNumber in iOS always be unique?

Question

When using attributesOfItemAtPath:error:, is NSFileSystemFileNumber always guaranteed to be unique for the device?

For example, I have a file with a certain NSFileSystemFileNumber, but a few days later I delete this file. If I create another file later on, is it possible that this new file can ever re-use the other file's NSFileSystemFileNumber, or will the NSFileSystemFileNumber always be unique?

Thanks!

Answer 1

NSFileManager Class Reference

NSFileSystemFileNumber

The key in a file attribute dictionary whose value indicates the file's filesystem file number. The corresponding value is an NSNumber object containing an unsigned long. The value corresponds to the value of st_ino, as returned by stat(2).

man 2 stat

ino_t st_ino; /* inode's number */

So this is an inode number. I believe inode can be reused by filesystem after original file is deleted.

Answer 2

The NSFileSystemFileNumber is just the file's inode number. It's unique to the file while the file exists, but once the file is gone, it could be reused at any time.