NixOS's reproducibility makes it ideal for building development environments. However, if you're used to other distros, you may encounter problems because NixOS has its own logic. We'll briefly explain this below.
On NixOS, it's recommended to only install common tools in the global environment, such as `git`, `vim`, `emacs`, `tmux`, `zsh`, etc. The development environment of each language should be an independent environment for each project.
You should NOT install the development environment of each language in the global environment. The project environment should be completely isolated from each other and will not affect each other.
We can create a development environment using `pkgs.mkShell { ... }` and open an interactive Bash shell of this development environment using `nix develop`.
To see how `pkgs.mkShell` works, let's take a look at [its source code](https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/mkshell/default.nix).
`pkgs.mkShell { ... }` is a special derivation (Nix package). Its `name`, `buildInputs`, and other parameters are customizable, and `shellHook` is a special parameter that will be executed when `nix develop` enters the environment.
description = "A Nix-flake-based Node.js development environment";
inputs = {
nixpkgs.url = "github:nixos/nixpkgs/nixos-23.05";
};
outputs = { self , nixpkgs ,... }: let
# system should match the system you are running on
# system = "x86_64-linux";
system = "x86_64-darwin";
in {
devShells."${system}".default = let
pkgs = import nixpkgs {
inherit system;
overlays = [
(self: super: rec {
nodejs = super.nodejs-18_x;
pnpm = super.nodePackages.pnpm;
yarn = (super.yarn.override { inherit nodejs; });
})
];
};
in pkgs.mkShell {
# create an environment with nodejs-18_x, pnpm, and yarn
packages = with pkgs; [
node2nix
nodejs
pnpm
yarn
];
shellHook = ''
echo "node `${pkgs.nodejs}/bin/node --version`"
'';
};
};
}
```
Create an empty folder, save the above configuration as `flake.nix`, and then execute `nix develop` (or more precisely, you can use `nix develop .#default`), you will find that you have entered a nodejs 18 development environment, you can use `node``npm``pnpm``yarn` and other commands. And when you just entered, `shellHook` was also executed, outputting the current version of nodejs.
Now let's take a look at `nix develop`, first read the help document output by `nix develop --help`:
```
Name
nix develop - run a bash shell that provides the build environment of a derivation
Synopsis
nix develop [option...] installable
# ......
```
It tells us that `nix develop` accepts a parameter `installable`, which means that we can enter the development environment of any installable Nix package through it, not just the environment created by `pkgs.mkShell`.
By default, `nix develop` will try to use the following attributes in the flake outputs:
-`devShells.<system>.default`
-`packages.<system>.default`
If we use `nix develop /path/to/flake#<name>` to specify the flake package address and flake output name, then `nix develop` will try the following attributes in the flake outputs:
-`devShells.<system>.<name>`
-`packages.<system>.<name>`
-`legacyPackages.<system>.<name>`
Now let's try it out. First, test it to confirm that We don't have `c++``g++` and other compilation-related commands in the current environment:
```shell
ryan in 🌐 aquamarine in ~
› c++
c++: command not found
ryan in 🌐 aquamarine in ~
› g++
g++: command not found
```
Then use `nix develop` to enter the build environment of the `hello` package in `nixpkgs`:
```shell
# login to the build environment of the package `hello`
ryan in 🌐 aquamarine in ~
› nix develop nixpkgs#hello
ryan in 🌐 aquamarine in ~ via ❄️ impure (hello-2.12.1-env)
› env | grep CXX
CXX=g++
ryan in 🌐 aquamarine in ~ via ❄️ impure (hello-2.12.1-env)
› c++ --version
g++ (GCC) 12.3.0
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
ryan in 🌐 aquamarine in ~ via ❄️ impure (hello-2.12.1-env)
› g++ --version
g++ (GCC) 12.3.0
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
```
We can see that the `CXX` environment variable have been set, and the `c++``g++` and other commands can be used normally now.
In addition, we can also call every build phase of the `hello` package normally:
> The default execution order of all build phases of a Nix package is: `$prePhases unpackPhase patchPhase $preConfigurePhases configurePhase $preBuildPhases buildPhase checkPhase $preInstallPhases installPhase fixupPhase installCheckPhase $preDistPhases distPhase $postPhases`
```shell
# unpack source code
ryan in 🌐 aquamarine in /tmp/xxx via ❄️ impure (hello-2.12.1-env)
The `nix build` command is used to build a software package and creates a symbolic link named `result` in the current directory, which points to the build result.
Here's an example:
```bash
# Build the package 'ponysay' from the 'nixpkgs' flake
There are other commands like `nix flake init`, which you can explore in [New Nix Commands][New Nix Commands]. For more detailed information, please refer to the documentation.
- [One too many shell, Clearing up with nix' shells nix shell and nix-shell - Yannik Sander](https://blog.ysndr.de/posts/guides/2021-12-01-nix-shells/)
