[Nix-dev] two versions of emacs installed

[Michael Raskin]

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On 07/10/2010 07:04 PM, Bryan Murdock wrote:
> The most intriguing feature of nixos for me is being able to have
> multiple versions of the same software installed.  I just got nixos
> running as a virtualbox guest and that's the first thing I tried and
> it didn't work.  I installed emacs 23:
> 
> nix-env -i emacs-23.2
> 
> and that worked just fine.  Then I tried to install emacs 22:
> 
> nix-env --preserve-installed -i emacs-22.3

Well, here you ask Nix not just to have these packages installed, but to
have them installed in the same environment. In this case it is
impossible to decide what should be "emacs" in the Nix profile (the
symlink set managed by nix-env) - Emacs 22 or Emacs 23.

If you run:

nix-build /etc/nixos/nixpkgs -A emacs22 -o emacs22
nix-build /etc/nixos/nixpkgs -A emacs23 -o emacs23
./emacs22/bin/emacs
./emacs23/bin/emacs

You will get two different versions of Emacs.
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