How to overwrite a symbolic link of a directory?

Question

There are two directories foo1 and foo2.

At first I make a directory symlink by ln -s foo1 bar. After that I want to change the symlink, so I typed ln -sf foo2 bar

But bar is still linked with foo1. Symlink foo2 is created inside of foo1.

What should I type when I want to replace foo1 by foo2?

I tested in three environments.

1. Ubuntu 12.04, ln (GNU coreutils) 8.13
2. CentOS 6.4, ln (GNU coreutils) 8.4
3. OS X 10.7.5, ln (without version)

Solution

The proper way to do this is to use the -n, --no-dereference option like so.

$ ln -snf foo2 bar

This causes ln to treat the existing symlink as a file. Otherwise, it dereferences bar to foo1, descends into foo1 and uses the original TARGET name as the LINK_NAME and that's why you end up with a symlink to foo2 being created inside the foo1 directory. The manpage on ln states the following...

-n, --no-dereference
       treat  LINK_NAME  as a normal file if it is a symbolic link to a
       directory

Below is the shell output on my Arch Linux desktop with version 8.21 of ln with and without the --no-dereference option, I got the same results you did without the --no-dereference option, but using the --no-dereference option it worked as expected.

$ mkdir foo1 foo2
$ ln -s foo1 bar
$ ls -l bar
  lrwxrwxrwx 1 drew users 4 Sep 17 12:51 bar -> foo1
$ ln -sf foo2 bar
$ ls -l bar
  lrwxrwxrwx 1 drew users 4 Sep 17 12:51 bar -> foo1
$ ls -l foo1
  total 0
  lrwxrwxrwx 1 drew users 4 Sep 17 12:51 foo2 -> foo2
$ ln -snf foo2 bar
$ ls -l bar
  lrwxrwxrwx 1 drew users 4 Sep 17 12:52 bar -> foo2

Comments

[ironsand]

Thanks for your answer. If it is environment dependent problem, I will write my environment. Which os are you using? what outputs ln --version?

[NikoKaranatsios]

FYI, I found this answer on the justlinux.com forums.

[ironsand]

Thanks druciferre! I even never thought that the ln command so often upgrade.

[ironsand]

I tested in osx also. ln works same as ubuntu and centos with the directory overwrite and ln -snf solve the problem. Even though ln -h is prefer option to use in osx.

[NikoKaranatsios]

@Tetsu, I also confirmed it on FreeBSD.

[lpapp]

Great, this is even working with busybox; many thanks!