What is “root project dir”? The source folder? It might not exist in a later phase of the applications life cycle…

Also the cwd might be anything. Totally depends on from which folder mix was called when compiling or from where release was actually started…

Under some very rare circumstances you do not even have a CWD.

Please be aware of those culprits, and try to avoid the usage in a compile time environment… Especially as those paths might not exist anymore at runtime…

From what you have written I assume that you want to distribute some file with your library/application and then read it in the user runtime. This is why there is priv/ directory and :code.priv_dir/1.

Then you can just ignore my words of warning.

Still I hope you do it in a way that ensures recompilation on change of the source files.

To be honest, implementing a “compiler” that can be added to the key with the same name in the project description is probably your best option.

That implies that your call File.cwd!() is executed at compile time. That explains why you see the dependency directory.

In other words:

defmodule MyLibrary do
  @cwd File.cwd! # this is executed at compile time

  def foo do
    IO.puts("cwd at compile time: #{@cwd}")
    IO.puts("cwd at runtime: #{File.cwd!}")
  end
end

Don’t read randomly from your users dir. Ask them to explicitely specify where to serach.