Bug 1114225

This is a subtle one, and essentially due to the difference between
"cwd" and "pwd".
realpath is working on the path provided correctly,
with "." referring to "cwd".

With /bin symlinked to /usr/bin, after one changes to /bin
you really are in the /usr/bin directory. I.E. the current
working directory '.' refers to /usr/bin

  $ cd /bin
  $ readlink /proc/$$/cwd
  /usr/bin

Other ways to determine the real path are:

  $ pwd -P
  /usr/bin

  $ realpath .
  /usr/bin

  $ echo "import os; print os.getcwd()" | python
  /usr/bin

Now what you're suggesting is that realpath should
be aware of "pwd", i.e. the $PWD env variable of the current shell.
The portable way to determine that is:

  $ pwd -L
  /bin

You're implying that realpath -L should also honor $PWD.
The readlink -P and -L options currently only affect the symlink and ..
resolution order, matching the functionality of cd -P and -L:

  /$ cd /
  /$ cd -P /bin/..
  usr$ cd /
  /$ cd -L /bin/..
  /$

I suppose one could also make -L honor $PWD ?
I.E. prepend $PWD to relative paths before further processing.
That also matches the current symlink resolution order behavior.
With that in place you could get what you wanted with:

  $ realpath -sL .
  /bin

Now you really wouldn't want to complicate the interface
and implementation of realpath unless there was a good use case
for resolving relative paths like this. That would only be
needed if you wanted to resolve a mixture of relative and absolute paths,
as you can already resolve multiple relative paths like this quite easily:

  $ realpath -s $PWD/{one,two}
  /bin/one
  /bin/two

Could you give more details on your use case?

thanks

This is a discussion we should be having upstream BTW.
Stas, could you copy you're initial query to coreutils
and I'll respond there.

Thanks for the detailed explanation.
In fact I wasn't properly realizing that
getcwd() and readlink /proc/$$/cwd all
return not what was provided to chdir()
because the symlink is already dereferenced
by chdir().

> The readlink -P and -L options currently only affect the symlink and ..
I guess you mean realpath, not readlink.

> Could you give more details on your use case?
There is currently none.
And I agree that -s alone should not use $PWD,
but -sL may. Feel free to close this if you
think -sL is unimportant.

Tracking this upstream. Though not sure yet if we'll change

Just pointer to the upstream thread : http://lists.gnu.org/archive/html/coreutils/2014-06/msg00087.html .