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diff --git a/src/nix/nix.md b/src/nix/nix.md index db60c59ff..0a90fa6c9 100644 --- a/src/nix/nix.md +++ b/src/nix/nix.md @@ -48,102 +48,112 @@ manual](https://nixos.org/manual/nix/stable/). # Installables -Many `nix` subcommands operate on one or more *installables*. These are -command line arguments that represent something that can be built in -the Nix store. Here are the recognised types of installables: - -* **Flake output attributes**: `nixpkgs#hello` - - These have the form *flakeref*[`#`*attrpath*], where *flakeref* is a - flake reference and *attrpath* is an optional attribute path. For - more information on flakes, see [the `nix flake` manual - page](./nix3-flake.md). 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: - - - If the path is within a Git repository, then the url will be of the form - `git+file://[GIT_REPO_ROOT]?dir=[RELATIVE_FLAKE_DIR_PATH]` - where `GIT_REPO_ROOT` is the path to the root of the git repository, - and `RELATIVE_FLAKE_DIR_PATH` is the path (relative to the directory - root) of the closest parent of the given path that contains a `flake.nix` within - the git repository. - If no such directory exists, then Nix will error-out. - - Note that the search will only include files indexed by git. In particular, files - which are matched by `.gitignore` or have never been `git add`-ed will not be - available in the flake. If this is undesirable, specify `path:<directory>` explicitly; - - For example, if `/foo/bar` is a git repository with the following structure: - ``` - . - └── baz - ├── blah - │ └── file.txt - └── flake.nix - ``` +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. - Then `/foo/bar/baz/blah` will resolve to `git+file:///foo/bar?dir=baz` +The following types of installable are supported by most commands: - - If the supplied path is not a git repository, then the url will have the form - `path:FLAKE_DIR_PATH` where `FLAKE_DIR_PATH` is the closest parent - of the supplied path that contains a `flake.nix` file (within the same file-system). - If no such directory exists, then Nix will error-out. - - For example, if `/foo/bar/flake.nix` exists, then `/foo/bar/baz/` will resolve to - `path:/foo/bar` +- [Flake output attribute](#flake-output-attribute) +- [Store path](#store-path) +- [Nix file](#nix-file), optionally qualified by an attribute path +- [Nix expression](#nix-expression), optionally qualified by an attribute path - 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, on - `x86_64-linux` `nix build nixpkgs#hello` will try to build the - attributes `packages.x86_64-linux.hello`, - `legacyPackages.x86_64-linux.hello` and `hello`. +For most commands, if no installable is specified, `.` as assumed. +That is, Nix will operate on the default flake output attribute of the flake in the current directory. -* **Store paths**: `/nix/store/v5sv61sszx301i0x6xysaqzla09nksnd-hello-2.10` +### Flake output attribute - These are paths inside the Nix store, or symlinks that resolve to a - path in the Nix store. +Example: `nixpkgs#hello` -* **Store derivations**: `/nix/store/p7gp6lxdg32h4ka1q398wd9r2zkbbz2v-hello-2.10.drv` +These have the form *flakeref*[`#`*attrpath*], where *flakeref* is a +[flake reference](./nix3-flake.md#flake-references) and *attrpath* is an optional attribute path. For +more information on flakes, see [the `nix flake` manual +page](./nix3-flake.md). 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:.`) - 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. +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: - [output path]: ../../glossary.md#gloss-output-path +- If the path is within a Git repository, then the url will be of the form + `git+file://[GIT_REPO_ROOT]?dir=[RELATIVE_FLAKE_DIR_PATH]` + where `GIT_REPO_ROOT` is the path to the root of the git repository, + and `RELATIVE_FLAKE_DIR_PATH` is the path (relative to the directory + root) of the closest parent of the given path that contains a `flake.nix` within + the git repository. + If no such directory exists, then Nix will error-out. - For example, `nix path-info` prints information about the output paths: + Note that the search will only include files indexed by git. In particular, files + which are matched by `.gitignore` or have never been `git add`-ed will not be + available in the flake. If this is undesirable, specify `path:<directory>` explicitly; - ```console - # nix path-info --json /nix/store/p7gp6lxdg32h4ka1q398wd9r2zkbbz2v-hello-2.10.drv - [{"path":"/nix/store/v5sv61sszx301i0x6xysaqzla09nksnd-hello-2.10",…}] + For example, if `/foo/bar` is a git repository with the following structure: + ``` + . + └── baz + ├── blah + │ └── file.txt + └── flake.nix ``` - If you want to operate on the store derivation itself, pass the - `--derivation` flag. + Then `/foo/bar/baz/blah` will resolve to `git+file:///foo/bar?dir=baz` + +- If the supplied path is not a git repository, then the url will have the form + `path:FLAKE_DIR_PATH` where `FLAKE_DIR_PATH` is the closest parent + of the supplied path that contains a `flake.nix` file (within the same file-system). + If no such directory exists, then Nix will error-out. + + For example, if `/foo/bar/flake.nix` exists, then `/foo/bar/baz/` will resolve to + `path:/foo/bar` + +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, on +`x86_64-linux` `nix build nixpkgs#hello` will try to build the +attributes `packages.x86_64-linux.hello`, +`legacyPackages.x86_64-linux.hello` and `hello`. + +### 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` -* **Nix attributes**: `--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. - When the `-f` / `--file` *path* option is given, installables are - interpreted as attribute paths referencing a value returned by - evaluating the Nix file *path*. +### Nix expression -* **Nix expressions**: `--expr '(import <nixpkgs> {}).hello.overrideDerivation (prev: { name = "my-hello"; })'`. +Example: `--expr 'import <nixpkgs> {}' hello` - When the `--expr` option is given, all installables are interpreted - as Nix expressions. You may need to specify `--impure` if the - expression references impure inputs (such as `<nixpkgs>`). +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. -For most commands, if no installable is specified, the default is `.`, -i.e. Nix will operate on the default flake output attribute of the -flake in the current directory. +You may need to specify `--impure` if the expression references impure inputs (such as `<nixpkgs>`). ## Derivation output selection |