Referencing the output of writeShellApplication as a package in another nix file

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1

I have a small inlined script I have added to my system packages like that:

systemPackages = with pkgs; [
...
      (
        pkgs.writeShellApplication {
          name = "screenshot";
          runtimeInputs = with pkgs; [ slurp swappy grim ];
          text = ''
            ${pkgs.grim}/bin/grim - g "$(${pkgs.slurp})" - | ${pkgs.swappy} -f -
          '';
        })
...
];

I would like to reference the script screenshot and gets its true path in another nix file (a sway keybind). How can I reference this “package” through the pkgs variable in the other nix file ?

2

You can do it through an overlay:

nixpkgs.overlays = [ (final: prev: {
  # use `final` instead of `pkgs` in overlay for dependencies, as a general principle
  your-screenshot-thing = final.writeShellApplication { ... };
}) ];

Then something like "${pkgs.your-screenshot-thing}/bin/screenshot"

3

Aside: you likely don’t need to use both writeShellApplication’s runtimeInputs and the string interpolation.

writeShellApplication will set a PATH that includes these packages for normal runtime path lookups, while string interpolation is writing in the absolute paths to the executables (requiring no runtimenpath lookups).

4

You can also do this by writing a module. I have an example defined in this file and you can search the repo for xmodmap-config to see how I make use of it in two other modules.

Hope this helps!

5

If you are doing it from separate modules, then an overlay would be the “de facto” way to create a long lived, globally available binding for your custom package.

If you are doing it in the same module then a simple let binding would do. Of course, writing a module is a valid option to be able to reference something like a package option, but seems excessive in this case.

6

An overlay is definitely what I was looking for !
Tested it and it worked exactly as intended.

Thank you all.

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