babashka/doc/nix.md

# Using Babashka with Nix

Babashka is [packaged](https://search.nixos.org/packages?type=packages&query=babashka) in nixpkgs and can be easily used from the Nix package manager.

The following assumes a recent installation of nix and uses the unstable [nix cli](https://nixos.org/manual/nix/stable/command-ref/new-cli/nix.html) and [Flakes](https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-flake.html).

To enable the unstable cli and flakes add the following to `/etc/nix/nix.conf`:

```
extra-experimental-features flakes nix-command
```

## Imperative install on Nix

To imperatively install nix for the current user, run `nix profile install babashka`.

## Declarative global install on NixOS

To install babashka for all users on a NixOS system, place it in `environment.systemPackages` in your `configuration.nix`:

```nix
{ pkgs, ... }:
{
    environment.systemPackages = with pkgs; [
        babashka
    ];
}
```

Then run `nixos-rebuild switch`, to activate the new configuration.

## Declarative per-user install with home-manager

You can install babashka for a specific user using [home-manager](https://github.com/nix-community/home-manager). Add the following to your `~/.config/nixpkgs/home.nix`:

```nix
{ pkgs, ... }:
{
    home.packages = with pkgs; [
        babashka
    ];
}
```

Then run `home-manager switch`, to activate the new configuration.

## Per project install with direnv

To make babashka available on a per-project basis, you can use [direnv](https://direnv.net/).

Create a file `.envrc` in the project directory with the following contents:

```
use flake
```

Create a file `flake.nix` in the project directory with the following contents:

```nix
{
  outputs = {nixpkgs, ...}: let
    supportedSystems = ["x86_64-linux" "x86_64-darwin"];
    forAllSystems = nixpkgs.lib.genAttrs supportedSystems;
    nixpkgsFor = system: import nixpkgs {inherit system;};
  in {
    devShell = forAllSystems (system: let
      pkgs = nixpkgsFor system;
    in
      pkgs.mkShell {
        packages = with pkgs; [
          babashka
        ];
      });
  };
}
```

After running `direnv allow`, babashka should be available on the `$PATH`, when you are inside the project directory.

## Write Babashka Application

You can write babashka scripts with native dependencies using [WriteBabashkaApplication](https://github.com/sohalt/write-babashka-application).

The WriteBabashkaApplication repository has an [example](https://github.com/Sohalt/write-babashka-application/tree/main/example) `flake.nix` using `cowsay` as an external dependency.


You can download that example, and then  build the application using `nix build` or run it using `nix run`.