How can you tell how many hardlinks a directory has in OSX from terminal?

Question

How can you tell how many hardlinks a directory has in OSX from terminal?

In OSX you can make hardlinks to directories. This is how Time Machine works. I would like to know which directories have hardlinks to them so I can see which directories are new to Time Machine.

I have tried ls -l and stat -f "%l %N" * but neither seem to give correct answers.

Anyone know how to do this?

Answer 1

ls -l is the correct way to display hardlink files in a directory.

From Wikipedia’s article on hard links:

Most modern operating systems don't allow hard links on directories to prevent endless recursion. In addition, hard links on directories would lead to inconsistency on parent directory entries. A notable exception to this is Mac OS X v10.5 (Leopard) which uses hard links on directories for the Time Machine backup mechanism only. Symbolic links and NTFS junction points are generally used instead for this purpose.

Answer 2

I don't think even Time Machine can hard link across file systems, by definitions. I believe making a hard link just creates a file (or directory) with the same inode number as the original, and inodes are only unique within a given file system.

I don't think there's any way to count how many symbolic links there are to a file or directory, since there can be symbolic links to files that are on unmounted volumes.

Update: When you create a directory, there are automatically two hard links to it. One from the directory itself (".") and one from its parent ("..") Doing an ls -ld on a directory will give you the number of hard links to it.