Does number of hardlinks to a directory correspond to the number of subdirectories in it?

Question

When displaying directories using ls -l, their number of links (the second field in the output) is at least two: one for the dir name and one for .

$ mkdir foo
$ ls -l
total 2
drwxr-xr-x  2 user   wheel  512  4 oct 14:02 foo

Is it safe to always assume that the number of links above 2 corresponds to the number of subdirectories in this dir (.. links) ?

Answer 1

While generally you can only use symbolic links to directories, which will not affect the link count, there are some circumstances where hard-links are possible for directories (IIRC OSX's TimeMachine feature uses such links) so it might not always be guaranteed.

You would be safer passing a scan using ls and grep (or perhaps find) to the wc command to count the number of sub-directories actually present rather than trying to guess from the current directories link count.

Answer 2

You are correct to observe that all directories contain . and .., so if you subtract two from the output of

ls -la | grep '^d' | wc -l

you should get the number of directories in your current working directory.

Answer 3

this does not answer your question about ls -l, but I use tree -d for this, it works very nicely.

Answer 4

I would use find

find ./foo -type d | wc -l

eventually with the -maxdepth option