CARGO-CHECK(1)

📦 version 1.82.0, in ubuntu jammy, ubuntu noble

cargo-check(1) — General Commands Manual — okay bestie, let's check some packages 💖✨

✨ NAME ✨

cargo-check — Check the current package. 💅

🌸 SYNOPSIS 🌸

cargo check [options]

💖 DESCRIPTION 💖

Okay so cargo check checks a local package and all of its dependencies for errors. It basically compiles the packages without doing the final step of code generation, which is faster than running cargo build. The compiler saves metadata files to disk so future runs reuse them if the source hasn't been modified. Some diagnostics and errors are only emitted during code generation, so they inherently won't be reported with cargo check. 😭

🎀 OPTIONS 🎀

📦 Package Selection 📦

By default, when no package selection options are given, the packages selected depend on the selected manifest file (based on the current working directory if --manifest-path is not given). If the manifest is the root of a workspace then the workspace's default members are selected, otherwise only the package defined by the manifest will be selected.

The default members of a workspace can be set explicitly with the workspace.default-members key in the root manifest. If this is not set, a virtual workspace will include all workspace members (equivalent to passing --workspace), and a non-virtual workspace will include only the root crate itself.

  • -p spec…, --package spec… — Check only the specified packages. See cargo-pkgid(1) for the SPEC format. This flag may be specified multiple times and supports common Unix glob patterns like *, ? and []. However, to avoid your shell accidentally expanding glob patterns before Cargo handles them, you must use single quotes or double quotes around each pattern. 💅
  • --workspace — Check all members in the workspace.
  • --all — Deprecated alias for --workspace.
  • --exclude SPEC… — Exclude the specified packages. Must be used in conjunction with the --workspace flag. This flag may be specified multiple times and supports common Unix glob patterns like *, ? and []. However, to avoid your shell accidentally expanding glob patterns before Cargo handles them, you must use single quotes or double quotes around each pattern.

🎯 Target Selection 🎯

When no target selection options are given, cargo check will check all binary and library targets of the selected packages. Binaries are skipped if they have required-features that are missing.

Passing target selection flags will check only the specified targets.

Note that --bin, --example, --test and --bench flags also support common Unix glob patterns like *, ? and []. However, to avoid your shell accidentally expanding glob patterns before Cargo handles them, you must use single quotes or double quotes around each glob pattern.

  • --lib — Check the package's library.
  • --bin name… — Check the specified binary. This flag may be specified multiple times and supports common Unix glob patterns.
  • --bins — Check all binary targets.
  • --example name… — Check the specified example. This flag may be specified multiple times and supports common Unix glob patterns.
  • --examples — Check all example targets.
  • --test name… — Check the specified integration test. This flag may be specified multiple times and supports common Unix glob patterns.
  • --tests — Check all targets in test mode that have the test = true manifest flag set. By default this includes the library and binaries built as unittests, and integration tests. Be aware that this will also build any required dependencies, so the lib target may be built twice (once as a unittest, and once as a dependency for binaries, integration tests, etc.). Targets may be enabled or disabled by setting the test flag in the manifest settings for the target.
  • --bench name… — Check the specified benchmark. This flag may be specified multiple times and supports common Unix glob patterns.
  • --benches — Check all targets in benchmark mode that have the bench = true manifest flag set. By default this includes the library and binaries built as benchmarks, and bench targets. Be aware that this will also build any required dependencies, so the lib target may be built twice (once as a benchmark, and once as a dependency for binaries, benchmarks, etc.). Targets may be enabled or disabled by setting the bench flag in the manifest settings for the target.
  • --all-targets — Check all targets. This is equivalent to specifying --lib --bins --tests --benches --examples.

🧚 Feature Selection 🧚

The feature flags allow you to control which features are enabled. When no feature options are given, the default feature is activated for every selected package.

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

  • -F features, --features features — Space or comma separated list of features to activate. Features of workspace members may be enabled with package-name/feature-name syntax. This flag may be specified multiple times, which enables all specified features.
  • --all-features — Activate all available features of all selected packages.
  • --no-default-features — Do not activate the default feature of the selected packages.

🔧 Compilation Options 🔧

  • --target triple — Check for the given architecture. The default is the host architecture. The general format of the triple is <arch><sub>-<vendor>-<sys>-<abi>. Run rustc --print target-list for a list of supported targets. This flag may be specified multiple times.

This may also be specified with the build.target config value at https://doc.rust-lang.org/cargo/reference/config.html.

Note that specifying this flag makes Cargo run in a different mode where the target artifacts are placed in a separate directory. See the build cache documentation at https://doc.rust-lang.org/cargo/guide/build-cache.html for more details.

  • -r, --release — Check optimized artifacts with the release profile. See also the --profile option for choosing a specific profile by name.
  • --profile name — Check with the given profile.

As a special case, specifying the test profile will also enable checking in test mode which will enable checking tests and enable the test cfg option. See rustc tests at https://doc.rust-lang.org/rustc/tests/index.html for more detail.

See the reference at https://doc.rust-lang.org/cargo/reference/profiles.html for more details on profiles.

  • --timings=fmts — Output information how long each compilation takes, and track concurrency information over time. Accepts an optional comma-separated list of output formats; --timings without an argument will default to --timings=html. Specifying an output format (rather than the default) is unstable and requires -Zunstable-options. Valid output formats:
    • html (unstable, requires -Zunstable-options): Write a human-readable file cargo-timing.html to the target/cargo-timings directory with a report of the compilation. Also write a report to the same directory with a timestamp in the filename if you want to look at older runs. HTML output is suitable for human consumption only, and does not provide machine-readable timing data.
    • json (unstable, requires -Zunstable-options): Emit machine-readable JSON information about timing information.

📁 Output Options 📁

  • --target-dir directory — Directory for all generated artifacts and intermediate files. May also be specified with the CARGO_TARGET_DIR environment variable, or the build.target-dir config value at https://doc.rust-lang.org/cargo/reference/config.html. Defaults to target in the root of the workspace.

🖥️ Display Options 🖥️

  • -v, --verbose — Use verbose output. May be specified twice for “very verbose” output which includes extra output such as dependency warnings and build script output. May also be specified with the term.verbose config value at https://doc.rust-lang.org/cargo/reference/config.html.
  • -q, --quiet — Do not print cargo log messages. May also be specified with the term.quiet config value at https://doc.rust-lang.org/cargo/reference/config.html.
  • --color when — Control 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.

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

  • --message-format fmt — The output format for diagnostic messages. Can be specified multiple times and consists of comma-separated values. Valid values:
    • human (default): Display in a human-readable text format. Conflicts with short and json.
    • short: Emit shorter, human-readable text messages. Conflicts with human and json.
    • json: Emit JSON messages to stdout. See the reference at https://doc.rust-lang.org/cargo/reference/external-tools.html#json-messages for more details. Conflicts with human and short.
    • json-diagnostic-short: Ensure the rendered field of JSON messages contains the “short” rendering from rustc. Cannot be used with human or short.
    • json-diagnostic-rendered-ansi: Ensure the rendered field of JSON messages contains embedded ANSI color codes for respecting rustc’s default color scheme. Cannot be used with human or short.
    • json-render-diagnostics: Instruct Cargo to not include rustc diagnostics in JSON messages printed, but instead Cargo itself should render the JSON diagnostics coming from rustc. Cargo’s own JSON diagnostics and others coming from rustc are still emitted. Cannot be used with human or short.

📜 Manifest Options 📜

  • --manifest-path path — Path to the Cargo.toml file. By default, Cargo searches for the Cargo.toml file in the current directory or any parent directory.
  • --ignore-rust-version — Ignore rust-version specification in packages.
  • --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 the following scenarios arises:
    • 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, such as in CI pipelines. 🎯

  • --offline — no internet for you, babe. This stops Cargo from touching the network for literally any reason. Without it, Cargo will just 💀 with an error the moment it needs the network and the network isn't there. With it, Cargo will try to keep going without the network if it possibly can.
⚠️ Lowkey important: this can give you different dependency resolution than online mode. Cargo restricts itself to crates that are already downloaded locally, even if a newer version exists as indicated in the local copy of the index. So yeah, your lockfile might come out different. 👀

Want to do it properly? Run the cargo-fetch(1) command to download your dependencies before you go offline. 🧚

May also be specified with the net.offline config value (https://doc.rust-lang.org/cargo/reference/config.html).

  • --frozen — the two-for-one special, bestie. Equivalent to specifying both --locked and --offline at the same time. Periodt. ✨
  • --lockfile-path PATH — moves your lockfile somewhere else. Instead of the default <workspace_root>/Cargo.lock, it goes to PATH. And PATH must end with Cargo.lock (like --lockfile-path /tmp/temporary-lockfile/Cargo.lock — see how it ends in Cargo.lock? yes ma'am 💅).

Heads up: giving --lockfile-path means it will ignore any existing lockfile at the default path, and instead either use the lockfile from PATH, or write a brand new lockfile into the PATH you gave it if there isn't one already. 🫶

Why would you even? Because this flag lets you run most commands in read-only directories, writing the lockfile into the PATH you provided. Iconic behaviour honestly. 👑

🚨 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 #14421 — https://github.com/rust-lang/cargo/issues/14421).

🌈 Common Options 🌈

  • +toolchain — if Cargo was installed with rustup, and the first argument to cargo starts with +, it gets read as a rustup toolchain name (things like +stable or +nightly). See the rustup documentation (https://rust-lang.github.io/rustup/overrides.html) for more on how toolchain overrides work. 🦋
  • --config KEY=VALUE or PATH — overrides a Cargo configuration value. The argument should be TOML syntax of KEY=VALUE, or you can hand it a path to an extra configuration file. You can use this flag multiple times if you're feeling spicy. 🌶️ See the command-line overrides section (https://doc.rust-lang.org/cargo/reference/config.html#command-line-overrides) for more info.
  • -C PATH — changes the current working directory before any of the operations you asked for get executed. This affects stuff like where cargo looks by default for the project manifest (Cargo.toml), and also the directories it searches when discovering .cargo/config.toml, for example. This option must appear before the command name, like cargo -C path/to/my-project build. 🎀
🚨 Nightly-only alert: 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).
  • -h, --help — prints help information. Your bestie when you're lost. 💖
  • -Z flag — unstable (nightly-only) flags to Cargo. Run cargo -Z help for details. iykyk ⭐

🍓 Miscellaneous Options 🍓

  • -j N, --jobs N — number of parallel jobs to run. May also be specified with the build.jobs config value (https://doc.rust-lang.org/cargo/reference/config.html). Defaults to the number of logical CPUs. If it's negative, it sets the maximum number of parallel jobs to the number of logical CPUs plus the value you provided. If a string default is provided, it sets the value back to defaults. And it should not be 0. 🙈
  • --keep-going — builds as many crates in the dependency graph as possible, instead of aborting the whole build on the first one that fails to build. 🔥

For example, if the current package depends on dependencies fails and works, one of which fails to build, cargo check -j1 may or may not build the one that succeeds (it depends on which one of the two builds Cargo picked to run first), whereas cargo check -j1 --keep-going would definitely run both builds, even if the one run first fails. No cap. 💪

  • --future-incompat-report — displays a future-incompat report for any future-incompatible warnings produced during execution of this command. 😭

See cargo-report(1)

🌸 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. Check the local package for errors:
cargo check
  1. Check all targets, including unit tests:
cargo check --all-targets --profile=test

🦋 SEE ALSO 🦋

cargo(1), cargo-build(1)

And that's a wrap on CARGO-CHECK(1), bestie!! 🎀 This whole thing came straight out of the Cargo manual for the cargo-check command — go check your stuff, stay locked and loaded, and remember: --locked is your friend in CI. Mwah. 💜✨🫶

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