forked from lix-project/lix
120 lines
3.6 KiB
Markdown
120 lines
3.6 KiB
Markdown
R""(
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# Examples
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* Create a new flake:
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```console
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# nix flake new hello
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# cd hello
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```
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* Build the flake in the current directory:
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```console
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# nix build
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# ./result/bin/hello
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Hello, world!
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```
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* Run the flake in the current directory:
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```console
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# nix run
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Hello, world!
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```
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* Start a development shell for hacking on this flake:
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```console
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# nix develop
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# unpackPhase
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# cd hello-*
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# configurePhase
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# buildPhase
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# ./hello
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Hello, world!
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# installPhase
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# ../outputs/out/bin/hello
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Hello, world!
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```
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# Description
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Nix is a tool for building software, configurations and other
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artifacts in a reproducible and declarative way. For more information,
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see the [Nix homepage](https://nixos.org/) or the [Nix
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manual](https://nixos.org/manual/nix/stable/).
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# Installables
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Many `nix` subcommands operate on one or more *installables*. These are
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command line arguments that represent something that can be built in
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the Nix store. Here are the recognised types of installables:
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* **Flake output attributes**: `nixpkgs#hello`
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These have the form *flakeref*[`#`*attrpath*], where *flakeref* is a
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flake reference and *attrpath* is an optional attribute path. For
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more information on flakes, see [the `nix flake` manual
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page](./nix3-flake.md). Flake references are most commonly a flake
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identifier in the flake registry (e.g. `nixpkgs`) or a path
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(e.g. `/path/to/my-flake` or `.`).
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If *attrpath* is omitted, Nix tries some default values; for most
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subcommands, the default is `defaultPackage.`*system*
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(e.g. `defaultPackage.x86_64-linux`), but some subcommands have
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other defaults. If *attrpath* *is* specified, *attrpath* is
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interpreted as relative to one or more prefixes; for most
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subcommands, these are `packages.`*system*,
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`legacyPackages.*system*` and the empty prefix. Thus, on
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`x86_64-linux` `nix build nixpkgs#hello` will try to build the
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attributes `packages.x86_64-linux.hello`,
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`legacyPackages.x86_64-linux.hello` and `hello`.
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* **Store paths**: `/nix/store/v5sv61sszx301i0x6xysaqzla09nksnd-hello-2.10`
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These are paths inside the Nix store, or symlinks that resolve to a
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path in the Nix store.
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* **Store derivations**: `/nix/store/p7gp6lxdg32h4ka1q398wd9r2zkbbz2v-hello-2.10.drv`
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Store derivations are store paths with extension `.drv` and are a
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low-level representation of a build-time dependency graph used
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internally by Nix. By default, if you pass a store derivation to a
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`nix` subcommand, it will operate on the *output paths* of the
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derivation. For example, `nix path-info` prints information about
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the output paths:
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```console
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# nix path-info --json /nix/store/p7gp6lxdg32h4ka1q398wd9r2zkbbz2v-hello-2.10.drv
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[{"path":"/nix/store/v5sv61sszx301i0x6xysaqzla09nksnd-hello-2.10",…}]
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```
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If you want to operate on the store derivation itself, pass the
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`--derivation` flag.
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* **Nix attributes**: `--file /path/to/nixpkgs hello`
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When the `-f` / `--file` *path* option is given, installables are
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interpreted as attribute paths referencing a value returned by
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evaluating the Nix file *path*.
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* **Nix expressions**: `--expr '(import <nixpkgs> {}).hello.overrideDerivation (prev: { name = "my-hello"; })'`.
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When the `--expr` option is given, all installables are interpreted
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as Nix expressions. You may need to specify `--impure` if the
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expression references impure inputs (such as `<nixpkgs>`).
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For most commands, if no installable is specified, the default is `.`,
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i.e. Nix will operate on the default flake output attribute of the
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flake in the current directory.
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# Nix stores
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Most `nix` subcommands operate on a *Nix store*.
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TODO: list store types, options
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)""
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