nix - Nix Reference Manual (original) (raw)

Warning
This program isexperimentaland its interface is subject to change.

Name

nix - a tool for reproducible and declarative configuration management

Synopsis

nix [option...] subcommand

where subcommand is one of the following:

Help commands:

Main commands:

Main commands:

Infrequently used commands:

Utility/scripting commands:

Commands for upgrading or troubleshooting your Nix installation:

Examples

# nix flake new hello  
# cd hello  
# nix build  
# ./result/bin/hello  
Hello, world!  
# nix run  
Hello, world!  
# nix develop  
# unpackPhase  
# cd hello-*  
# configurePhase  
# buildPhase  
# ./hello  
Hello, world!  
# installPhase  
# ../outputs/out/bin/hello  
Hello, world!

Description

Nix is a tool for building software, configurations and other artifacts in a reproducible and declarative way. For more information, see the Nix homepage or the Nix manual.

Installables

Warning
Installables are part of the unstablenix-command experimental feature, and subject to change without notice.

Many nix subcommands operate on one or more installables. These are command line arguments that represent something that can be realised in the Nix store.

The following types of installable are supported by most commands:

For most commands, if no installable is specified, . is assumed. That is, Nix will operate on the default flake output attribute of the flake in the current directory.

Flake output attribute

Warning
Flake output attribute installables depend on both theflakesandnix-commandexperimental features, and subject to change without notice.

Example: nixpkgs#hello

These have the form _flakeref_[#_attrpath_], where flakeref is aflake reference and attrpath is an optional attribute path. For more information on flakes, see the nix flake manual page. Flake references are most commonly a flake identifier in the flake registry (e.g. nixpkgs), or a raw path (e.g. /path/to/my-flake or . or ../foo), or a full URL (e.g. github:nixos/nixpkgs or path:.)

When the flake reference is a raw path (a path without any URL scheme), it is interpreted as a path: or git+file: url in the following way:

.  
└── baz  
    ├── blah  
    │   └── file.txt  
    └── flake.nix

Then /foo/bar/baz/blah will resolve to git+file:///foo/bar?dir=baz

If attrpath is omitted, Nix tries some default values; for most subcommands, the default is packages.system.default(e.g. packages.x86_64-linux.default), but some subcommands have other defaults. If attrpath is specified, attrpath is interpreted as relative to one or more prefixes; for most subcommands, these are packages.system,legacyPackages.*system* and the empty prefix. Thus, onx86_64-linux nix build nixpkgs#hello will try to build the attributes packages.x86_64-linux.hello,legacyPackages.x86_64-linux.hello and hello.

If attrpath begins with . then no prefixes or defaults are attempted. This allows the form _flakeref_[#._attrpath_], such as github:NixOS/nixpkgs#.lib.fakeSha256 to avoid a search of packages.*system*.lib.fakeSha256

Store path

Example: /nix/store/v5sv61sszx301i0x6xysaqzla09nksnd-hello-2.10

These are paths inside the Nix store, or symlinks that resolve to a path in the Nix store.

A store derivation is also addressed by store path.

Example: /nix/store/p7gp6lxdg32h4ka1q398wd9r2zkbbz2v-hello-2.10.drv

If you want to refer to an output path of that store derivation, add the output name preceded by a caret (^).

Example: /nix/store/p7gp6lxdg32h4ka1q398wd9r2zkbbz2v-hello-2.10.drv^out

All outputs can be referred to at once with the special syntax ^*.

Example: /nix/store/p7gp6lxdg32h4ka1q398wd9r2zkbbz2v-hello-2.10.drv^*

Nix file

Example: --file /path/to/nixpkgs hello

When the option -f / --file path [attrpath...] is given, installables are interpreted as the value of the expression in the Nix file at path. If attribute paths are provided, commands will operate on the corresponding values accessible at these paths. The Nix expression in that file, or any selected attribute, must evaluate to a derivation.

Nix expression

Example: --expr 'import <nixpkgs> {}' hello

When the option --expr expression [attrpath...] is given, installables are interpreted as the value of the of the Nix expression. If attribute paths are provided, commands will operate on the corresponding values accessible at these paths. The Nix expression, or any selected attribute, must evaluate to a derivation.

You may need to specify --impure if the expression references impure inputs (such as <nixpkgs>).

Derivation output selection

Derivations can have multiple outputs, each corresponding to a different store path. For instance, a package can have a bin output that contains programs, and a dev output that provides development artifacts like C/C++ header files. The outputs on which nix commands operate are determined as follows:

# nix build 'nixpkgs#glibc^dev,static'  
# ls ./result-dev/include/ ./result-static/lib/  
…

and likewise, using a store path to a "drv" file to specify the derivation: 

# nix build '/nix/store/gzaflydcr6sb3567hap9q6srzx8ggdgg-glibc-2.33-78.drv^dev,static'  
…

For -e/--expr and -f/--file, the derivation output is specified as part of the attribute path: 

$ nix build -f '<nixpkgs>' 'glibc^dev,static'  
$ nix build --impure -E 'import <nixpkgs> { }' 'glibc^dev,static'

This syntax is the same even if the actual attribute path is empty: 

$ nix build -E 'let pkgs = import <nixpkgs> { }; in pkgs.glibc' '^dev,static'  
# nix path-info --closure-size --eval-store auto --store https://cache.nixos.org 'nixpkgs#glibc^*'  
/nix/store/g02b1lpbddhymmcjb923kf0l7s9nww58-glibc-2.33-123                 33208200  
/nix/store/851dp95qqiisjifi639r0zzg5l465ny4-glibc-2.33-123-bin             36142896  
/nix/store/kdgs3q6r7xdff1p7a9hnjr43xw2404z7-glibc-2.33-123-debug          155787312  
/nix/store/n4xa8h6pbmqmwnq0mmsz08l38abb06zc-glibc-2.33-123-static          42488328  
/nix/store/q6580lr01jpcsqs4r5arlh4ki2c1m9rv-glibc-2.33-123-dev             44200560

and likewise, using a store path to a "drv" file to specify the derivation: 

# nix path-info --closure-size '/nix/store/gzaflydcr6sb3567hap9q6srzx8ggdgg-glibc-2.33-78.drv^*'  
…  
# nix eval 'nixpkgs#libxml2.meta.outputsToInstall'  
[ "bin" "man" ]

a command like nix shell nixpkgs#libxml2 will provide only those two outputs by default.
Note that a store derivation (given by its .drv file store path) doesn't have any attributes like meta, and thus this case doesn't apply to it.

Nix stores

Most nix subcommands operate on a Nix store. The various store types are documented in theStore Typessection of the manual.

The same information is also available from the nix help-stores command.

Shebang interpreter

The nix command can be used as a #! interpreter. Arguments to Nix can be passed on subsequent lines in the script.

Verbatim strings may be passed in double backtick (``) quotes. Sequences of n backticks of 3 or longer are parsed as n-1 literal backticks. A single space before the closing `` is ignored if present.

--file and --expr resolve relative paths based on the script location.

Examples:

#!/usr/bin/env nix
#! nix shell --file ``<nixpkgs>`` hello cowsay --command bash

hello | cowsay

or with flakes:

#!/usr/bin/env nix
#! nix shell nixpkgs#bash nixpkgs#hello nixpkgs#cowsay --command bash

hello | cowsay

or with an expression:

#! /usr/bin/env nix
#! nix shell --impure --expr ``
#! nix with (import (builtins.getFlake "nixpkgs") {});
#! nix terraform.withPlugins (plugins: [ plugins.openstack ])
#! nix ``
#! nix --command bash

terraform "$@"

or with cascading interpreters. Note that the #! nix lines don't need to follow after the first line, to accommodate other interpreters.

#!/usr/bin/env nix
//! ```cargo
//! [dependencies]
//! time = "0.1.25"
//! ```
/*
#!nix shell nixpkgs#rustc nixpkgs#rust-script nixpkgs#cargo --command rust-script
*/
fn main() {
    for argument in std::env::args().skip(1) {
        println!("{}", argument);
    };
    println!("{}", std::env::var("HOME").expect(""));
    println!("{}", time::now().rfc822z());
}
// vim: ft=rust

Options

Miscellaneous global options

Note

See man nix.conf for overriding configuration settings with command line flags.