Nix/src/nix/show-derivation.md

R""(

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.

)""