When using ls -l, I noticed that directories start with 2 hard links, and gain one for each subdirectory. I understand that the current directory link . counts as one link and the parent directory link .. of each subdirectory counts as a hard link, but:
Why don't subfiles count towards hard links when subdirectories do?
Why does the parent directory link .. count as a hard link for both this directory and the parent directory?
Assume the following directory tree
/a
/b
/c
/d
Then directory b at path /a/b has 4 hard links. The links are the following:
b (from the parent directory). (from the directory itself)c/..d/..Files don't count against the link count of a directory, because files do not have a nested .. directory, thus do not point back to the directory.
We can calculate the number of hardlinks for each directory shown above:
a (from /).b/..c (from b).d (from b).