# Hacking

This section provides some notes on how to hack on Nix. To get the latest version of Nix from GitHub:

    $ git clone https://github.com/NixOS/nix.git
    $ cd nix

To build Nix for the current operating system/architecture use

    $ nix-build

or if you have a flake-enabled nix:

    $ nix build

This will build `defaultPackage` attribute defined in the `flake.nix` file. To build for other platforms add one of the following suffixes to it: aarch64-linux, i686-linux, x86_64-darwin, x86_64-linux. i.e.

    $ nix-build -A defaultPackage.x86_64-linux

To build all dependencies and start a shell in which all environment variables are set up so that those dependencies can be found:

    $ nix-shell

or if you have a flake-enabled nix:

    $ nix develop

To get a shell with a different compilation environment (e.g. stdenv, gccStdenv, clangStdenv, clang11Stdenv):

    $ nix-shell -A devShells.x86_64-linux.clang11StdenvPackages

or if you have a flake-enabled nix:

    $ nix develop .#clang11StdenvPackages

To build Nix itself in this shell:

    [nix-shell]$ ./bootstrap.sh
    [nix-shell]$ ./configure $configureFlags --prefix=$(pwd)/outputs/out
    [nix-shell]$ make -j $NIX_BUILD_CORES

To install it in `$(pwd)/outputs` and test it:

    [nix-shell]$ make install
    [nix-shell]$ make installcheck -j $NIX_BUILD_CORES
    [nix-shell]$ ./outputs/out/bin/nix --version
    nix (Nix) 3.0

To run a functional test:

    make tests/test-name-should-auto-complete.sh.test

To run the unit-tests for C++ code:

    make check

If you have a flakes-enabled Nix you can replace:

    $ nix-shell

by:

    $ nix develop