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Scripts

Most projects out there have a bunch of shell scripts lying around.

Questions arise as to where to define scripts and how to provide the tooling to make sure they work for all developers.

A simple example defining silly-example script:

devenv.nix
{ pkgs, ... }:

{
  packages = [ pkgs.curl pkgs.jq ]; # (1)!

  scripts.silly-example.exec = ''
    curl "https://httpbin.org/get?$1" | jq '.args'
  '';
}
  1. See Packages for an explanation.

Since scripts are exposed when we enter the environment, we can rely on packages executables being available.

$ devenv shell
Building shell ...
Entering shell ...

(devenv) $ silly-example foo=1
{
  "foo": "1"
}

Pinning packages inside scripts

Sometimes we don't want to expose the tools to the shell but still make sure they are pinned in a script:

devenv.nix
{ pkgs, ... }:

{
  scripts.silly-example.exec = ''
    ${pkgs.curl}/bin/curl "https://httpbin.org/get?$1" | ${pkgs.jq}/bin/jq '.args'
  '';
}

When a package is interpolated in a string, you're referring to the path where it is located.

$ devenv shell
Building shell ...
Entering shell ...

(devenv) $ silly-example foo=1
{
  "foo": "1"
}

Scripts can also have an optional description, which can be useful in your enterShell.

devenv.nix
{ pkgs, config, lib, ... }:

{
  packages = [ pkgs.curl pkgs.jq ];

  scripts.silly-example.exec = ''curl "https://httpbin.org/get?$1" | jq .args'';
  scripts.silly-example.description = "curls httpbin with provided arg";

  scripts.serious-example.exec = ''${pkgs.cowsay}/bin/cowsay "$*"'';
  scripts.serious-example.description = ''echoes args in a very serious manner'';

  enterShell = ''
      echo
      echo 🦾 Helper scripts you can run to make your development richer:
      echo 🦾
      ${pkgs.gnused}/bin/sed -e 's| |••|g' -e 's|=| |' <<EOF | ${pkgs.util-linuxMinimal}/bin/column -t | ${pkgs.gnused}/bin/sed -e 's|^|🦾 |' -e 's|••| |g'
      ${lib.generators.toKeyValue {} (lib.mapAttrs (name: value: value.description) config.scripts)}
      EOF
      echo
    '';
}

$ devenv shell
Building shell ...
Entering shell ...

🦾 Helper scripts you can run to make your development richer:
🦾
🦾 serious-example  echoes args in a very serious manner
🦾 silly-example    curls httpbin with provided arg

(devenv) $