Nix: What is it and what should I use it with?

Hello, Habr!

At Typeable, we wanted to publish a short series of articles on how Nix helps us (and hinders us a little) in development. But after spending a little time looking for similar material here, we were surprised to find that there is no sensible introduction to Nix on Habré to which one could refer.

@snizovtsev C++, , . :)

.

?

NixOS, , Nix ( ) Linux. :

$ sh <(curl -L https://nixos.org/nix/install)
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

. MacOS, , . MacOS .

Nix

Nix, : Nix nixpkgs , NixOS. .

Nix — . ML (SML, OCaml, Haskell), , , .

.

$ nix repl
Welcome to Nix version 2.3.10. Type :? for help.

nix-repl> 
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

Nix . , .

nix-repl> "Hello " + "World!"
"Hello World!"

nix-repl> add = a: b: a + b

nix-repl> add 1 2
3
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, Nix, .

nix-repl> addOne = add 1

nix-repl> addOne 3
4
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, , Nix (attribute sets Nix).

nix-repl> list = [ 1 2 3 ]

nix-repl> set = { a = 1; b = list; }     

nix-repl> set
{ a = 1; b = [ ... ]; }

nix-repl> set.b
[ 1 2 3 ]
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

let...in



. , , , .

fac.nix



:

let
  fac = n:
    if n == 0
    then 1
    else n * fac (n - 1);
in { inherit fac; }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

inherit



"" . let fac = ... in { fac = fac; }



.

$ nix repl fac.nix
Welcome to Nix version 2.3.10. Type :? for help.

Loading 'fac.nix'...
Added 1 variables.

nix-repl> fac 3 
6
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

REPL, Nix , , .

Nix import



, .

mul.nix



:

let
  mul = a: b: a * b;
in { inherit mul; }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

fac.nix



:

let
  multMod = import ./mul.nix;
  fac = n:
    if n == 0
    then 1
    else multMod.mul n (fac (n - 1));
in { inherit fac; }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

— , , ? Nix with



, , .

fac.nix



with



:

with import ./mul.nix;
let
  fac = n:
    if n == 0
    then 1
    else mul n (fac (n - 1));
in { inherit fac; }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

— Nix.

, , , Derivation



. Derivation



— , - . C, "Hello World!", derivation :

Derive([("out","/nix/store/1nq46fyv3629slgxnagqn2c01skp7xrq-hello-world","","")],[("/nix/store/60xqp516mkfhf31n6ycyvxppcknb2dwr-build-hello.drv",["out"])],["/nix/store/wiviq2xyz0ylhl0qcgfgl9221nkvvxfj-hello.c"],"x86_64-linux","/nix/store/r5lh8zg768swlm9hxxfrf9j8gwyadi72-build-hello",[],[("builder","/nix/store/r5lh8zg768swlm9hxxfrf9j8gwyadi72-build-hello"),("name","hello-world"),("out","/nix/store/1nq46fyv3629slgxnagqn2c01skp7xrq-hello-world"),("src","/nix/store/wiviq2xyz0ylhl0qcgfgl9221nkvvxfj-hello.c"),("system","x86_64-linux")])
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, , , , , : . , /nix/store



. , Nix , (sandbox). .

, ! , Nix derivation



, .

simple-derivation/default.nix



:

{ pkgs ? import <nixpkgs> {} }:

derivation {
  name = "hello-world";
  builder = pkgs.writeShellScript "build-hello" ''
    ${pkgs.coreutils}/bin/mkdir -p $out/bin
    ${pkgs.gcc}/bin/gcc $src -o $out/bin/hello -O2
  '';
  src = ./hello.c;
  system = builtins.currentSystem;
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

. , — , pkgs



. , : import <nixpkgs> {}



.

derivation



— , : name



— , builder



— , src



— , system



— , .

writeShellScript



— nixpkgs



, . Nix .

nix build



, .

$ nix build -f ./simple-derivation/default.nix
[1 built]

$ ./result/bin/hello 
Hello World!
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

nix build



, result



, /nix/store



.

$ ls -l result 
lrwxrwxrwx 1 user users 50 Mar 29 17:53 result -> /nix/store/vpcddray35g2jrv40dg1809xrmz73awi-simple

$ find /nix/store/vpcddray35g2jrv40dg1809xrmz73awi-simple
/nix/store/vpcddray35g2jrv40dg1809xrmz73awi-simple
/nix/store/vpcddray35g2jrv40dg1809xrmz73awi-simple/bin
/nix/store/vpcddray35g2jrv40dg1809xrmz73awi-simple/bin/hello
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

,

derivation



— , Nix . , cowsay



.

{ lib, stdenv, fetchurl, perl }:

stdenv.mkDerivation rec {
  version = "3.03+dfsg2";
  pname = "cowsay";

  src = fetchurl {
    url = "http://http.debian.net/debian/pool/main/c/cowsay/cowsay_${version}.orig.tar.gz";
    sha256 = "0ghqnkp8njc3wyqx4mlg0qv0v0pc996x2nbyhqhz66bbgmf9d29v";
  };

  buildInputs = [ perl ];

  postBuild = ''
    substituteInPlace cowsay --replace "%BANGPERL%" "!${perl}/bin/perl" \
      --replace "%PREFIX%" "$out"
  '';

  installPhase = ''
    mkdir -p $out/{bin,man/man1,share/cows}
    install -m755 cowsay $out/bin/cowsay
    ln -s cowsay $out/bin/cowthink
    install -m644 cowsay.1 $out/man/man1/cowsay.1
    ln -s cowsay.1 $out/man/man1/cowthink.1
    install -m644 cows/* -t $out/share/cows/
  '';

  meta = with lib; {
    description = "A program which generates ASCII pictures of a cow with a message";
    homepage = "https://en.wikipedia.org/wiki/Cowsay";
    license = licenses.gpl1;
    platforms = platforms.all;
    maintainers = [ maintainers.rob ];
  };
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

.

stdenv



— derivation



, : , . — setup



, builder



.

 $ nix build nixpkgs.stdenv

 $ find result/
result/
result/setup
result/nix-support

$ wc -l result/setup 
1330 result/setup
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

mkDerivation



— , derivation



.

, Arch Linux Gentoo, . , , (buildInputs



) .

Nix . , Nix Typeable, . Stay tuned!

, Nix Nix pills.