[Nix-dev] nix profiles and env vars - proposal

[Marc Weber]

Lluís Batlle has asked about how to add env vars today.

I've posted a small patch in the past:
http://thread.gmane.org/gmane.linux.distributions.nixos/44

I'd vote for this way to implement it:

Make the builder.pl creating the final profiile execute
nix-support/post-install/* scripts
passing the list of derivations to be installed.

Then you can add a derivation to your profile providing a post-install
script collecting env vars from $out/nix-support/env writing the result
to $profile/bash-sourceme (or such)

Example:

PythonLibA
$out/nix-support/env contents
  PYTHONPATH=/nix/store/xxxxxxxxx-PythonLibA/.../site-packages:$PYTHONPATH

PythonLibB
$out/nix-support/env contents
  PYTHONPATH=/nix/store/xxxxxxxxx-PythonLibB/.../site-packages:$PYTHONPATH

perl lib
$out/nix-support/env contents
  PERLIMPORTS=/nix/store/xxxxxxxxx-perl-lib/lib/...:$PYTHONPATH

So the post install script iterates over those files and creates one
containing

  PYTHONPATH=/nix/store/xxxxxxxxx-PythonLibA/.../site-packages:$PYTHONPATH
  PYTHONPATH=/nix/store/xxxxxxxxx-PythonLibB/.../site-packages:$PYTHONPATH
  PERLIMPORTS=/nix/store/xxxxxxxxx-perl-lib/lib/...:$PYTHONPATH


If you don't install the post install script nohting will change.

How do you like this?

Marc Weber