nix3-show-derivation(1)

Warning: This program is experimental and its interface is subject to change.

Name
nix show-derivation - show the contents of a store derivation

Synopsis
nix show-derivation [option…] installables…

Examples

•   Show the store derivation that results from evaluating the Hello package:

    # nix show-derivation nixpkgs#hello
    {
    "/nix/store/s6rn4jz1sin56rf4qj5b5v8jxjm32hlk-hello-2.10.drv": {
      …
    }
    }

•   Show the full derivation graph (if available) that produced your NixOS system:

    # nix show-derivation -r /run/current-system

•   Print all files fetched using fetchurl by Firefox’s dependency graph:

    # nix show-derivation -r nixpkgs#firefox \
    | jq -r '.[] | select(.outputs.out.hash and .env.urls) | .env.urls' \
    | uniq | sort

    Note that .outputs.out.hash selects fixed-output derivations (derivations that produce output with a specified content hash), while .env.urls selects derivations with a urls attribute.

Description
This command prints on standard output a JSON representation of the store derivations to which installables evaluate. Store derivations are used internally by Nix. They are store paths with extension .drv that represent the build-time dependency graph to which a Nix expression evaluates.

By default, this command only shows top-level derivations, but with --recursive, it also shows their dependencies.

The JSON output is a JSON object whose keys are the store paths of the derivations, and whose values are a JSON object with the following fields:

•   outputs: Information about the output paths of the derivation. This is a JSON object with one member per output, where the key is the output name and the value is a JSON object with these fields:

    •   path: The output path.

    •   hashAlgo: For fixed-output derivations, the hashing algorithm (e.g. sha256), optionally prefixed by r: if hash denotes a NAR hash rather than a flat file hash.

    •   hash: For fixed-output derivations, the expected content hash in base-16.

    Example:

    "outputs": {
    "out": {
      "path": "/nix/store/2543j7c6jn75blc3drf4g5vhb1rhdq29-source",
      "hashAlgo": "r:sha256",
      "hash": "6fc80dcc62179dbc12fc0b5881275898f93444833d21b89dfe5f7fbcbb1d0d62"
    }
    }

•   inputSrcs: A list of store paths on which this derivation depends.

•   inputDrvs: A JSON object specifying the derivations on which this derivation depends, and what outputs of those derivations. For example,

    "inputDrvs": {
    "/nix/store/6lkh5yi7nlb7l6dr8fljlli5zfd9hq58-curl-7.73.0.drv": ["dev"],
    "/nix/store/fn3kgnfzl5dzym26j8g907gq3kbm8bfh-unzip-6.0.drv": ["out"]
    }

    specifies that this derivation depends on the dev output of curl, and the out output of unzip.

•   system: The system type on which this derivation is to be built (e.g. x86_64-linux).

•   builder: The absolute path of the program to be executed to run the build. Typically this is the bash shell (e.g. /nix/store/r3j288vpmczbl500w6zz89gyfa4nr0b1-bash-4.4-p23/bin/bash).

•   args: The command-line arguments passed to the builder.

•   env: The environment passed to the builder.

Options

•   --debugger
    start an interactive environment if evaluation fails

•   --recursive / -r
    Include the dependencies of the specified derivations.

Common evaluation options:

•   --arg name expr
    Pass the value expr as the argument name to Nix functions.

•   --argstr name string
    Pass the string string as the argument name to Nix functions.

•   --eval-store store-url
    The Nix store to use for evaluations.

•   --impure
    Allow access to mutable paths and repositories.

•   --include / -I path
    Add path to the list of locations used to look up <...> file names.

•   --override-flake original-ref resolved-ref
    Override the flake registries, redirecting original-ref to resolved-ref.

Common flake-related options:

•   --commit-lock-file
    Commit changes to the flake’s lock file.

•   --inputs-from flake-url
    Use the inputs of the specified flake as registry entries.

•   --no-registries
    Don’t allow lookups in the flake registries. This option is deprecated; use --no-use-registries.

•   --no-update-lock-file
    Do not allow any updates to the flake’s lock file.

•   --no-write-lock-file
    Do not write the flake’s newly generated lock file.

•   --override-input input-path flake-url
    Override a specific flake input (e.g. dwarffs/nixpkgs). This implies --no-write-lock-file.

•   --recreate-lock-file
    Recreate the flake’s lock file from scratch.

•   --update-input input-path
    Update a specific flake input (ignoring its previous entry in the lock file).

Options that change the interpretation of installables:

•   --derivation
    Operate on the store derivation rather than its outputs.

•   --expr expr
    Interpret installables as attribute paths relative to the Nix expression expr.

•   --file / -f file
    Interpret installables as attribute paths relative to the Nix expression stored in file. If file is the character -, then a Nix expression will be read from standard input. Implies --impure.