How to force creation of a symbolic link?

Question

I have a particular directory full of other directories organized (named) by date. For ease of reference, I have a symlink called current pointing to the latest one.

In the script that creates new date directories, I wish to create or fix the current symlink to point to the newest directory once created.

I thought the appropriate command would just be, e.g.,

ln -fs 2017-03-01 current

If the current symlink doesn't exist yet, this works.

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However, if the current symlink has already been created (and points, let us say, at the directory 2017-02-28), this doesn't work:

Instead of removing the symlink current and creating a new symlink current which points to 2017-03-01, the result will instead be a broken symlink called 2017-03-01 pointing to itself, resting inside the directory 2017-02-28 (which is where the symlink current pointed and still points).

This baffled me, so I read the specs for ln. Turns out this is expected behavior:

SYNOPSIS

ln [-fs] [-L|-P] source_file target_file

ln [-fs] [-L|-P] source_file... target_dir

DESCRIPTION

...

The second synopsis form shall be assumed when the final operand names an existing directory.

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It seems, then, that there is no way whatsoever to repoint a symlink that currently points to a directory to a new target, where the new target has a name different from the name of the symlink. So ln -fs doesn't work the way I thought it did.

Must I rm current, or is there another approach I've overlooked?

Answer 1

In GNU's ln, there is ln -n, which would allow re-pointing a symlink:

$ mkdir dir1 dir2
$ ln -s dir1 sym
# dir1/
# dir2/
# sym -> dir1/

$ ln -nsf dir2 sym
# dir1/
# dir2/
# sym -> dir2/

BSD coreutils uses the flag -h the same way -n would be used, but it is likely the binary may support -n just for compatibility with GNU.

Repointing it to the same location also requires the -f flag.