Why “ln -s A B” is different from “ln -s A/ B”?

Question

Isn't A the same as A/ ?

Why they are treated differently by ln ?

Answer 1

EDIT: I misread the question - I thought you were asking about ls, but you were asking about ln - thanks Martijn for the comment.

Anyway, I don't see any difference on my side:

$ mkdir 1
$ touch 2
$ ls -l
total 4
drwxr-xr-x 2 user user 4096 2010-12-20 21:48 1
-rw-r--r-- 1 user user    0 2010-12-20 21:48 2
$ ln -s 1 3
$ ln -s 1/ 3s
$ ln -s 2 4
$ ln -s 2/ 4s
$ ls -l
total 4
drwxr-xr-x 2 user user 4096 2010-12-20 21:48 1
-rw-r--r-- 1 user user    0 2010-12-20 21:48 2
lrwxrwxrwx 1 user user    1 2010-12-20 21:48 3 -> 1
lrwxrwxrwx 1 user user    2 2010-12-20 21:48 3s -> 1/
lrwxrwxrwx 1 user user    1 2010-12-20 21:48 4 -> 2
lrwxrwxrwx 1 user user    2 2010-12-20 21:48 4s -> 2/

As for ls from my previous edit...

There may be differences e.g. on symlinks:

$ ls -l
total 0
$ mkdir 1
$ echo 1>1/a
$ find
.
./1
./1/a
$ ln -s 1 2
$ ls -l
total 4
drwxr-xr-x 2 user user 4096 2010-12-19 13:17 1
lrwxrwxrwx 1 user user    1 2010-12-19 13:17 2 -> 1
$ ls -l 1
total 4
-rw-r--r-- 1 user user 1 2010-12-19 13:17 a
$ ls -l 2
lrwxrwxrwx 1 user user 1 2010-12-19 13:17 2 -> 1
$ ls -l 2/
total 4
-rw-r--r-- 1 user user 1 2010-12-19 13:17 a

It is better to think of it like this:

• ls A lists A
• ls A/ actually lists A/., where . is a special file denoting current directory

Thus, for symlinks ls A list the symlink, while ls A/ == ls A/. list the contents of the folder pointed to by the symlink.

For more details, take a look here:

• http://pubs.opengroup.org/onlinepubs/9699919799/

section 4.12 Pathname Resolution.