forked from lix-project/lix
make descriptions of each installable type an own subsection
this is easier to edit, provides anchors for free, and renders correctly on the terminal without additional effort.
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Valentin Gagarin
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108
src/nix/nix.md
108
src/nix/nix.md
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@ -50,23 +50,31 @@ manual](https://nixos.org/manual/nix/stable/).
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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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the Nix store.
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* **Flake output attributes**: `nixpkgs#hello`
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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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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 raw path
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(e.g. `/path/to/my-flake` or `.` or `../foo`), or a full URL
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(e.g. `github:nixos/nixpkgs` or `path:.`)
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Here are the recognised types of installables:
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When the flake reference is a raw path (a path without any URL
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scheme), it is interpreted as a `path:` or `git+file:` url in the following
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way:
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## Flake output attributes
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- If the path is within a Git repository, then the url will be of the form
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Example: `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 raw path
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(e.g. `/path/to/my-flake` or `.` or `../foo`), or a full URL
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(e.g. `github:nixos/nixpkgs` or `path:.`)
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When the flake reference is a raw path (a path without any URL
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scheme), it is interpreted as a `path:` or `git+file:` url in the following
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way:
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- If the path is within a Git repository, then the url will be of the form
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`git+file://[GIT_REPO_ROOT]?dir=[RELATIVE_FLAKE_DIR_PATH]`
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where `GIT_REPO_ROOT` is the path to the root of the git repository,
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and `RELATIVE_FLAKE_DIR_PATH` is the path (relative to the directory
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@ -89,7 +97,7 @@ the Nix store. Here are the recognised types of installables:
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Then `/foo/bar/baz/blah` will resolve to `git+file:///foo/bar?dir=baz`
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- If the supplied path is not a git repository, then the url will have the form
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- If the supplied path is not a git repository, then the url will have the form
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`path:FLAKE_DIR_PATH` where `FLAKE_DIR_PATH` is the closest parent
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of the supplied path that contains a `flake.nix` file (within the same file-system).
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If no such directory exists, then Nix will error-out.
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@ -97,53 +105,57 @@ the Nix store. Here are the recognised types of installables:
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For example, if `/foo/bar/flake.nix` exists, then `/foo/bar/baz/` will resolve to
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`path:/foo/bar`
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If *attrpath* is omitted, Nix tries some default values; for most
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subcommands, the default is `packages.`*system*`.default`
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(e.g. `packages.x86_64-linux.default`), 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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If *attrpath* is omitted, Nix tries some default values; for most
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subcommands, the default is `packages.`*system*`.default`
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(e.g. `packages.x86_64-linux.default`), 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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## Store paths
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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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Example: `/nix/store/v5sv61sszx301i0x6xysaqzla09nksnd-hello-2.10`
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* **Store derivations**: `/nix/store/p7gp6lxdg32h4ka1q398wd9r2zkbbz2v-hello-2.10.drv`
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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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By default, if you pass a [store derivation] path to a `nix` subcommand, the command will operate on the [output path]s of the derivation.
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## Store derivations
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[output path]: ../../glossary.md#gloss-output-path
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Example: `/nix/store/p7gp6lxdg32h4ka1q398wd9r2zkbbz2v-hello-2.10.drv`
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For example, `nix path-info` prints information about the output paths:
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By default, if you pass a [store derivation] path to a `nix` subcommand, the command will operate on the [output path]s of the derivation.
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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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[output path]: ../../glossary.md#gloss-output-path
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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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For example, `nix path-info` prints information about the output paths:
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* **Nix attributes**: `--file /path/to/nixpkgs hello`
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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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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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If you want to operate on the store derivation itself, pass the
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`--derivation` flag.
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* **Nix expressions**: `--expr '(import <nixpkgs> {}).hello.overrideDerivation (prev: { name = "my-hello"; })'`.
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## Nix attributes
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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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Example: `--file /path/to/nixpkgs hello`
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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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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
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Example: `--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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## Derivation output selection
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