nix3-flake-metadata - Man Page

nix flake metadata [option…] flake-url

• Show what dwarffs resolves to:

# nix flake metadata dwarffs
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"
}

This command shows information about the flake specified by the flake reference flake-url. It resolves the flake reference using the flake registry , 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.

• --json

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

• --no-pretty

  Print compact JSON output on a single line, even when the output is a terminal. Some commands may print multiple JSON objects on separate lines.

            See `--pretty`.

• --pretty

  Print multi-line, indented JSON output for readability.

            Default: indent if output is to a terminal.

            This option is only effective when `--json` is also specified.