Name¶

nix flake metadata - show flake metadata

Synopsis¶

nix flake metadata [option…] flake-url

Examples¶

•

Show what nixpkgs resolves to:

# nix flake metadata nixpkgs
Resolved URL:  github:edolstra/dwarffs
Locked URL:    github:edolstra/dwarffs/f691e2c991e75edb22836f1dbe632c40324215c5
Description:   A filesystem that fetches DWARF debug info from the Internet on demand
Path:          /nix/store/769s05vjydmc2lcf6b02az28wsa9ixh1-source
Revision:      f691e2c991e75edb22836f1dbe632c40324215c5
Last modified: 2021-01-21 15:41:26
Inputs:
├───nix: github:NixOS/nix/6254b1f5d298ff73127d7b0f0da48f142bdc753c
│   ├───lowdown-src: github:kristapsdz/lowdown/1705b4a26fbf065d9574dce47a94e8c7c79e052f
│   └───nixpkgs: github:NixOS/nixpkgs/ad0d20345219790533ebe06571f82ed6b034db31
└───nixpkgs follows input 'nix/nixpkgs'

•

Show information about dwarffs in JSON format:

# nix flake metadata dwarffs --json | jq .
{
"description": "A filesystem that fetches DWARF debug info from the Internet on demand",
"lastModified": 1597153508,
"locked": {


  "lastModified": 1597153508,


  "narHash": "sha256-VHg3MYVgQ12LeRSU2PSoDeKlSPD8PYYEFxxwkVVDRd0=",


  "owner": "edolstra",


  "repo": "dwarffs",


  "rev": "d181d714fd36eb06f4992a1997cd5601e26db8f5",


  "type": "github"
},
"locks": { ... },
"original": {


  "id": "dwarffs",


  "type": "indirect"
},
"originalUrl": "flake:dwarffs",
"path": "/nix/store/hang3792qwdmm2n0d9nsrs5n6bsws6kv-source",
"resolved": {


  "owner": "edolstra",


  "repo": "dwarffs",


  "type": "github"
},
"resolvedUrl": "github:edolstra/dwarffs",
"revision": "d181d714fd36eb06f4992a1997cd5601e26db8f5",
"url": "github:edolstra/dwarffs/d181d714fd36eb06f4992a1997cd5601e26db8f5"
}

Description¶

This command shows information about the flake specified by the flake reference flake-url. It resolves the flake reference using the flake registry (./nix3-registry.md), fetches it, and prints some meta data. This includes:

• Resolved URL: If flake-url is a flake identifier, then this is the flake reference that specifies its actual location, looked up in the flake registry.
• Locked URL: A flake reference that contains a commit or content hash and thus uniquely identifies a specific flake version.
• Description: A one-line description of the flake, taken from the description field in flake.nix.
• Path: The store path containing the source code of the flake.
• Revision: The Git or Mercurial commit hash of the locked flake.
• Revisions: The number of ancestors of the Git or Mercurial commit of the locked flake. Note that this is not available for github flakes.
• Last modified: For Git or Mercurial flakes, this is the commit time of the commit of the locked flake; for tarball flakes, it’s the most recent timestamp of any file inside the tarball.
• Inputs: The flake inputs with their corresponding lock file entries.

With --json, the output is a JSON object with the following fields:

• original and originalUrl: The flake reference specified by the user (flake-url) in attribute set and URL representation.
• resolved and resolvedUrl: The resolved flake reference (see above) in attribute set and URL representation.
• locked and lockedUrl: The locked flake reference (see above) in attribute set and URL representation.
• description: See Description above.
• path: See Path above.
• revision: See Revision above.
• revCount: See Revisions above.
• lastModified: See Last modified above.
• locks: The contents of flake.lock.

Options¶

•

--json
Produce output in JSON format, suitable for consumption by another program.

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).