nix-pills/pills/16/config-foo-bar.txt

$ nix repl
nix-repl> pkgs = import <nixpkgs> {}
nix-repl> pkgs.config
{ }
nix-repl> pkgs = import <nixpkgs> { config = { foo = "bar"; }; }
nix-repl> pkgs.config
{ foo = "bar"; }
Update documentation after Nix 2.0 switch In #89 it has been reported that the third step can't be done as `nix-repl` doesn't evaluate anymore on 18.09 and unstable as in both cases an evaluation error will be thrown. First of all this may confuse new users who want to learn Nix, but don't know the ecosystem sufficiently to understand why the install failed. As recent NixOS versions (unstable and 18.09) use Nix 2.0 by default and unstable doesn't evaluate with Nix 1.x anymore it should be a safe thing to do now. This patch covers two aspects: * Using Nix 2.0: I replayed the installation steps with `nix-env` to ensure that the steps and explanations provided in the first three chapters are still valid. * Replacing `nix-repl` references: most of the cases it was sufficient to replace `nix-repl` with the newly introduced command `nix repl`. In chapter three `nix-repl` was used to demonstrate the installation of a package with `nix-env`. I decided to use `nix-index` as demo package as I figured this tool to be extremely helpful to locate packages by output files. The explanation that Nix is not only a tool for package/derivation management, but a functional language as well was moved to chapter four where the basics of the language were actually covered. This change is just a first step towards an updated series, in the future we may want to use even more Nix 2.0 features (such as `nix-build` vs. `nix build` with `nix log`). Fixes #89 Possibly supersedes #71 2018-12-05 18:56:44 -05:00			`$ nix repl`
port pill #16 2017-08-17 09:11:10 -04:00			`nix-repl> pkgs = import <nixpkgs> {}`
			`nix-repl> pkgs.config`
			`{ }`
			`nix-repl> pkgs = import <nixpkgs> { config = { foo = "bar"; }; }`
			`nix-repl> pkgs.config`
			`{ foo = "bar"; }`