Re: [PATCH v2] ln: add the --relative option

[Pádraig Brady]

On 02/23/2012 09:28 PM, Eric Blake wrote:
> On 02/23/2012 12:50 PM, address@hidden wrote:
>> From: Harald Hoyer <address@hidden>
>>
>> With the "--relative --symbolic" options, ln computes the relative
>> symbolic link for the user.
>>
>> So, ln works just as cp, but creates relative symbolic links instead
>> of copying the file.
> 
> In general, I like the idea.  I will point out that we now have realpath
> that also can compute relative locations to an arbitrary starting point,
> so we probably ought to share the code between the two programs rather
> than rewriting it.

I like the functionality too.
As Eric points out, the new `realpath` util has the
relative path generation logic in it, which should be reused.
To demonstrate the equivalence you could implement this
functionality modulo option handling using `realpath` like:

ln--relative() {
  target="$1"; link_name="$2"
  rtarget="$(realpath -m "$target" --relative-to "$(dirname "$link_name")")"
  ln -s -v "$rtarget" "$link_name"
}

Now given the simplicity of the above, there is the argument
that new options within ln are not needed. We've discussed
on and off the idea of a contrib/ folder in coreutils to
provide generally useful but higher level commands like this.
Worth considering at least.

cheers,
Pádraig.