CARGO-METADATA(1)

📦 version 1.79.0, in ubuntu jammy, ubuntu noble

💖 CARGO-METADATA(1) 💖

General Commands Manual · the one where Cargo spills the tea in JSON

✨ NAME ✨

cargo-metadata — machine-readable metadata about the current package

okay so basically it's Cargo talking in robot so your tools can understand it 🫶

🌸 SYNOPSIS 🌸

cargo metadata [options]

🎀 DESCRIPTION 🎀

It spits out JSON to stdout containing all the info about the workspace members and the resolved dependencies of the current package. Like, everything. The whole vibe.

⚠️ heads up bestie: the format of the output is subject to change in future versions of Cargo. So please, for the love of everything, include the --format-version flag — it future-proofs your code so you actually get the format you're expecting. For more on that whole situation, scroll to "Compatibility" below 👇

There's also a Rust API for reading the metadata if you'd rather not hand-parse JSON like it's 2009: the cargo_metadata crate at https://crates.io/crates/cargo_metadata. Slay.

🌈 OUTPUT FORMAT 🌈

🦋 Compatibility 🦋

Within the same output format version, compatibility is maintained — except in some scenarios. Here's a non-exhaustive list of changes that are not considered incompatible:

  • Adding new fields — new fields get added when needed. Reserving this helps Cargo evolve without bumping the format version too often. It's giving "growth mindset" 💅
  • Adding new values for enum-like fields — same energy as adding new fields. Keeps metadata evolving without stagnation.
  • Changing opaque representations — the inner representations of some fields are implementation details. For example, fields related to "Source ID" are treated as opaque identifiers to differentiate packages or sources. Consumers shouldn't rely on those representations unless it's specified. do NOT build on sand, bestie

🌟 JSON format 🌟

The JSON output has the following format:

{
    /* Array of all packages in the workspace.
       It also includes all feature-enabled dependencies unless --no-deps is used.
    */
    "packages": [
        {
            /* The name of the package. */
            "name": "my-package",
            /* The version of the package. */
            "version": "0.1.0",
            /* The Package ID for referring to the
               package within the document and as the `--package` argument to many commands
            */
            "id": "file:///path/to/my-package#0.1.0",
            /* The license value from the manifest, or null. */
            "license": "MIT/Apache-2.0",
            /* The license-file value from the manifest, or null. */
            "license_file": "LICENSE",
            /* The description value from the manifest, or null. */
            "description": "Package description.",
            /* The source ID of the package, an "opaque" identifier representing
               where a package is retrieved from. See "Compatibility" above for
               the stability guarantee.

               This is null for path dependencies and workspace members.

               For other dependencies, it is a string with the format:
               - "registry+URL" for registry-based dependencies.
                 Example: "registry+https://github.com/rust-lang/crates.io-index"
               - "git+URL" for git-based dependencies.
                 Example: "git+https://github.com/rust-lang/cargo?rev=5e85ba14aaa20f8133863373404cb0af69eeef2c#5e85ba14aaa20f8133863373404cb0af69eeef2c"
               - "sparse+URL" for dependencies from a sparse registry
                 Example: "sparse+https://my-sparse-registry.org"

and that's the format bestie, more coming ✨

The value after the + is not explicitly defined, and may change between versions of Cargo and may not directly correlate to other things, such as registry definitions in a config file. New source kinds may be added in the future which will have different + prefixed identifiers. / "source": null, / Array of dependencies declared in the package's manifest. / "dependencies": [ { / The name of the dependency. / "name": "bitflags", / The source ID of the dependency. May be null, see description for the package source. / "source": "registry+https://github.com/rust-lang/crates.io-index", / The version requirement for the dependency. Dependencies without a version requirement have a value of "". */ "req": "^1.0", / The dependency kind. "dev", "build", or null for a normal dependency. / "kind": null, / If the dependency is renamed, this is the new name for the dependency as a string. null if it is not renamed. / "rename": null, / Boolean of whether or not this is an optional dependency. / "optional": false, / Boolean of whether or not default features are enabled. / "uses_default_features": true, / Array of features enabled. / "features": [], / The target platform for the dependency. null if not a target dependency. / "target": "cfg(windows)", / The file system path for a local path dependency. not present if not a path dependency. / "path": "/path/to/dep", / A string of the URL of the registry this dependency is from. If not specified or null, the dependency is from the default registry (crates.io). / "registry": null } ], / Array of Cargo targets. / "targets": [ { / Array of target kinds.

  • lib targets list the crate-type values from the manifest such as "lib", "rlib", "dylib", "proc-macro", etc. (default ["lib"])
  • binary is ["bin"]
  • example is ["example"]
  • integration test is ["test"]
  • benchmark is ["bench"]
  • build script is ["custom-build"] / "kind": [ "bin" ], / Array of crate types.
  • lib and example libraries list the crate-type values from the manifest such as "lib", "rlib", "dylib", "proc-macro", etc. (default ["lib"])
  • all other target kinds are ["bin"] / "crate_types": [ "bin" ], / The name of the target. / "name": "my-package", / Absolute path to the root source file of the target. / "src_path": "/path/to/my-package/src/main.rs", / The Rust edition of the target. Defaults to the package edition. / "edition": "2018", / Array of required features. This property is not included if no required features are set. / "required-features": ["feat1"], / Whether the target should be documented by cargo doc. / "doc": true, / Whether or not this target has doc tests enabled, and the target is compatible with doc testing. / "doctest": false, / Whether or not this target should be built and run with --test / "test": true } ], / Set of features defined for the package. Each feature maps to an array of features or dependencies it enables. / "features": { "default": [ "feat1" ], "feat1": [], "feat2": [] }, / Absolute path to this package's manifest. / "manifest_path": "/path/to/my-package/Cargo.toml", / Package metadata. This is null if no metadata is specified. / "metadata": { "docs": { "rs": { "all-features": true } } }, / List of registries to which this package may be published. Publishing is unrestricted if null, and forbidden if an empty array. / "publish": [ "crates-io" ], / Array of authors from the manifest. Empty array if no authors specified. / "authors": [ "Jane Doe <user@example.com>" ], / Array of categories from the manifest. / "categories": [ "command-line-utilities" ], / Optional string that is the default binary picked by cargo run. / "default_run": null, / Optional string that is the minimum supported rust version / "rust_version": "1.56", / Array of keywords from the manifest. / "keywords": [ "cli" ], / The readme value from the manifest or null if not specified. / "readme": "README.md", / The repository value from the manifest or null if not specified. / "repository": "https://github.com/rust-lang/cargo", / The homepage value from the manifest or null if not specified. / "homepage": "https://rust-lang.org", / The documentation value from the manifest or null if not specified. / "documentation": "https://doc.rust-lang.org/stable/std", / The default edition of the package. Note that individual targets may have different editions. / "edition": "2018", / Optional string that is the name of a native library the package is linking to. / "links": null, } ], / Array of members of the workspace. Each entry is the Package ID for the package. / "workspace_members": [ "file:///path/to/my-package#0.1.0", ], / Array of default members of the workspace. Each entry is the Package ID for the package. / "workspace_default_members": [ "file:///path/to/my-package#0.1.0", ], // The resolved dependency graph for the entire workspace. The enabled // features are based on the enabled features for the "current" package. // Inactivated optional dependencies are not listed. // // This is null if --no-deps is specified. // // By default, this includes all dependencies for all target platforms. // The --filter-platform flag may be used to narrow to a specific // target triple. "resolve": { / Array of nodes within the dependency graph. Each node is a package. / "nodes": [ { / The Package ID of this node. / "id": "file:///path/to/my-package#0.1.0", / The dependencies of this package, an array of Package IDs. / "dependencies": [ "https://github.com/rust-lang/crates.io-index#bitflags@1.0.4" ], / The dependencies of this package. This is an alternative to "dependencies" which contains additional information. In particular, this handles renamed dependencies. / "deps": [ { / The name of the dependency's library target. If this is a renamed dependency, this is the new name. / "name": "bitflags", / The Package ID of the dependency. / "pkg": "https://github.com/rust-lang/crates.io-index#bitflags@1.0.4" / Array of dependency kinds. Added in Cargo 1.40. / "dep_kinds": [ { / The dependency kind. "dev", "build", or null for a normal dependency. */
                                           "kind": null,
                                           /* The target platform for the dependency.
                                              null if not a target dependency.
                                           */
                                           "target": "cfg(windows)"
                                       }
                                   ]
                               }
                           ],
                           /* Array of features enabled on this package. */
                           "features": [
                               "default"
                           ]
                       }
                   ],
                   /* The root package of the workspace.
                      This is null if this is a virtual workspace. Otherwise it is
                      the Package ID of the root package.
                   */
                   "root": "file:///path/to/my-package#0.1.0",
               },
               /* The absolute path to the build directory where Cargo places its output. */
               "target_directory": "/path/to/my-package/target",
               /* The version of the schema for this metadata structure.
                  This will be changed if incompatible changes are ever made.
               */
               "version": 1,
               /* The absolute path to the root of the workspace. */
               "workspace_root": "/path/to/my-package"
               /* Workspace metadata.
                  This is null if no metadata is specified. */
               "metadata": {
                   "docs": {
                       "rs": {
                           "all-features": true
                       }
                   }
               }
           }

okay so that's the whole JSON blob, bestie, you made it through 😭🫶

📝 Notes

✨ OPTIONS ✨

🎯 Output Options

  • --no-deps — literally just gives you info about the workspace members, no dependency fetching, no extras. keep it local, queen.
  • --format-version version — tells Cargo which version of the output format you want. right now 1 is the only possible value, so yeah, it's giving "one option only" energy 💅
  • --filter-platform triple — this filters the resolve output so it only includes deps for the given target triple https://doc.rust-lang.org/cargo/appendix/glossary.html#target. Without this flag, the resolve includes all targets. fr fr, all of them.
heads up bestie: the deps listed in the "packages" array still include all dependencies. Every package definition is meant to be an unaltered reproduction of the info inside Cargo.toml. no edits, no filter, no cap 💀

🌸 Feature Selection

The feature flags are how you control which features get enabled. When you don't pass any feature options at all, the default feature is activated for every selected package. every single one. ✨

See the features documentation https://doc.rust-lang.org/cargo/reference/features.html#command-line-feature-options for more details.

  • -F features, --features features — a space or comma separated list of features to activate. You can enable features of workspace members with the package-name/feature-name syntax. You can also pass this flag multiple times, and that enables all the features you specified. 💖
  • --all-features — activate every available feature of all selected packages. go feral, babe.
  • --no-default-features — do not activate the default feature of the selected packages. 🚫

🎀 Display Options

  • -v, --verbose — use verbose output. You can specify it twice for "very verbose" output, which includes extra output like dependency warnings and build script output. Can also be set with the term.verbose config value https://doc.rust-lang.org/cargo/reference/config.html. 👑
  • -q, --quiet — don't print cargo log messages. Can also be set with the term.quiet config value https://doc.rust-lang.org/cargo/reference/config.html. 🤫
  • --color when — controls when colored output is used. Valid values:
    • auto (default): automatically detect if color support is available on the terminal. 🦋
    • always: always display colors. 🌈
    • never: never display colors. 🚫

Can also be set with the term.color config value https://doc.rust-lang.org/cargo/reference/config.html.

🧚 Manifest Options

  • --manifest-path path — the path to the Cargo.toml file. By default, Cargo searches for the Cargo.toml file in the current directory or any parent directory. 🔍
  • --locked — asserts that the exact same dependencies and versions are used as when the existing Cargo.lock file was originally generated. Cargo will exit with an error when either of these scenarios comes up:
    • The lock file is missing. 😭
    • Cargo attempted to change the lock file due to a different dependency resolution. 💀

It may be used in environments where deterministic builds are desired, like in CI pipelines. ✨

  • --offline — prevents Cargo from accessing the network for any reason. Without this flag, Cargo stops with an error if it needs to access the network and the network isn't available. With this flag, Cargo will attempt to proceed without the network if possible.
beware, bestie: this may result in a different dependency resolution than online mode. Cargo restricts itself to crates that are downloaded locally, even if there might be a newer version as indicated in the local copy of the index. See the cargo-fetch(1) command to download dependencies before going offline. 🙈

Can also be set with the net.offline config value https://doc.rust-lang.org/cargo/reference/config.html.

  • --frozen — equivalent to specifying both --locked and --offline at once. two-for-one, iconic. ❄️

💅 Common Options

  • +toolchain — if Cargo has been installed with rustup, and the first argument to cargo begins with +, it's interpreted as a rustup toolchain name (like +stable or +nightly). See the rustup documentation https://rust-lang.github.io/rustup/overrides.html for more info on how toolchain overrides work. 🛠️
  • --config KEY=VALUE or PATH — overrides a Cargo configuration value. The argument should be in TOML syntax of KEY=VALUE, or given as a path to an extra configuration file. This flag may be specified multiple times. See the command-line overrides section https://doc.rust-lang.org/cargo/reference/config.html#command-line-overrides for more information. ⚙️
  • -C PATH — changes the current working directory before executing any specified operations. This affects things like where cargo looks by default for the project manifest (Cargo.toml), and also the directories searched for discovering .cargo/config.toml, for example. This option must appear before the command name, like cargo -C path/to/my-project build.
this option is only available on the nightly channel https://doc.rust-lang.org/book/appendix-07-nightly-rust.html and requires the -Z unstable-options flag to enable (see #10098 https://github.com/rust-lang/cargo/issues/10098). no stable for you, sorry babe 😭
  • -h, --help — prints help information. 🫶
  • -Z flag — unstable (nightly-only) flags to Cargo. Run cargo -Z help for details. 🌙

🌍 ENVIRONMENT

See the reference https://doc.rust-lang.org/cargo/reference/environment-variables.html for details on environment variables that Cargo reads. 📖

🚦 EXIT STATUS

  • 0: Cargo succeeded. 🎉
  • 101: Cargo failed to complete. 💀

⭐ EXAMPLES

  1. Output JSON about the current package:
cargo metadata --format-version=1

👑 SEE ALSO

cargo(1), cargo-pkgid(1), Package ID Specifications https://doc.rust-lang.org/cargo/reference/pkgid-spec.html, JSON messages https://doc.rust-lang.org/cargo/reference/external-tools.html#json-messages

and that's the whole page, bestie!! 🎀 the footer on this one is just the manpage name itself — CARGO-METADATA(1) — no fancy version string or date hanging out down there, so that's your source/version-and-date situation: it's the CARGO-METADATA(1) page, periodt. 💖✨ now go run it and slay 🦋

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