Windows – How to Find Hard Links

It's not about the GUI, it's specifically about TextEdit's strategy for saving changes: it does not write in place on the existing file, but rather it first writes a new one, and when that's completed it removes the old one and renames the new one to the old one's names. Many editors (programs that conceptually alter a file "in place"), GUI or not, use this strategy for safety purposes (you won't lose both the new and old versions if there's a crash at a very unfortunate moment just when the writing is taking place), but as you noticed it "breaks" hard links.

One example of a non-interactive, non-GUI editor program with this behavior is perl with the -i ("in-place edits") command-line option switch...:

$ touch za.txt
$ ln za.txt zo.txt
$ echo ciao >za.txt
$ cat zo.txt 
ciao
$ perl -i -p -e 's/a/b/' zo.txt
$ cat zo.txt
cibo
$ cat za.txt
ciao

I think the answer is (quoted from some helpful guy) :

What you have to consider is the way an application/program works on a file.

Some edit the file directly, and they should work perfectly fine with hardlinks. Although I didn't knew the "fileinfo difference" problem until now ...

Other applications copy the file and then delete the old one when they save their edited version. This programs obviously break the hard link with that hidden copy operation. What they save is no longer the file they had opened. When they then delete the old version, they remove this single hardlink from the directory. Other hardlinks remain, and so you get two files in the end.

So yes - hardlinks can and will break - which limits their usefulness - badly thought.

correct me if wrong