[Nix-dev] Debugging nixpkgs

[Rob Vermaas]

> For now, I am still stuck in figuring out why gfortran won't build on
> my MacOS X system. Is there a way to prevent nix-build from deleting
> its temporary work directory if the build fails? Seeing its state at
> the point of failure would help me to analyse the problem.

$ nix-env --help
  ...
  --keep-failed / -K: keep temporary directories of failed builds
  ...