Exploring Cargo Commands (with examples)
Cargo is a package manager for the Rust programming language. It helps with building, testing, and managing Rust projects. One useful feature of Cargo is its built-in help command, which provides detailed information about Cargo and its subcommands. In this article, we will explore eight different use cases of the cargo help command.
Use Case 1: Display general help
Code:
cargo help
Motivation:
This command allows developers to quickly access general information about Cargo and its various subcommands. It is especially useful for beginners who are learning Rust and want to gain a high-level understanding of Cargo’s capabilities.
Explanation:
Running cargo help displays an overview of available Cargo subcommands, grouped by categories. It also includes a brief description of each subcommand.
Example Output:
Usage: cargo [OPTIONS] <SUBCOMMAND>
Cargo is a package manager for the Rust programming language.
Options:
-v, --version Print version info and exit
-h, --help Print this message and exit
--list List installed commands
--explain EXPLAIN Provide detailed explanation of an error message
-Z FLAG ... Unstable (nightly-only) flags to Cargo
Some common cargo commands include:
build Compile the current project
check Analyze the current project and report errors, but don't build object files
new Create a new cargo project
run Build and execute src/main.rs
test Run the tests
bench Run the benchmarks
doc Build this project's and its dependencies' documentation
clean Remove the target directory
...
Use Case 2: Display help for a subcommand
Code:
cargo help build
Motivation:
This command is useful when you want to get more detailed information about a specific Cargo subcommand. It helps you understand the various options and arguments available for that subcommand.
Explanation:
Running cargo help subcommand displays detailed information about the specified subcommand. It includes a description, usage syntax, available options, and examples.
Example Output:
cargo-build - Compile the current project
Usage: cargo build [OPTIONS]
Options:
-h, --help Print this message and exit
-p, --package PACKAGE_NAME Build the specified package, including its dependencies.
--all Build all packages in the workspace
...
--release Build artifacts in release mode, with optimizations
...
Use Case 3: Display help for a specific subcommand option
Code:
cargo help build --release
Motivation:
This use case helps when you want to understand a specific option or argument within a subcommand. It allows you to access detailed information about that particular option.
Explanation:
By appending the option or argument after the subcommand, cargo help subcommand --option provides detailed information about that specific option. It includes a description, the option’s usage syntax, and any additional information.
Example Output:
--release Build artifacts in release mode, with optimizations
By default, Cargo compiles your code with optimizations aimed at making
your code run as fast as possible. This includes running all tests, applying
a number of optimizations to the code, and potentially shrinking code
size.
This option disables those optimizations and tends to produce smaller,
faster-to-compile code but the resulting code will run slower. This can be
useful for debugging purposes, particularly if you want to provide a minimal
reproduction of an issue or if you are working on the Cargo codebase itself
and don't care about the optimizations.
Use Case 4: Display help for unstable nightly-only flags
Code:
cargo help -Z
Motivation:
This use case is handy for Rust developers using the nightly version of Rust, which includes unstable features. It provides information about available unstable flags specific to the nightly version.
Explanation:
Running cargo help -Z lists the unstable nightly-only flags available in the Cargo command. It includes a description of each flag and its usage.
Example Output:
-Z FLAG ... Unstable (nightly-only) flags to Cargo
The `-Z` flag allows the usage of various unstable (nightly-only) flags in
`cargo`. These flags are used for debugging, experimenting, and potentially
breaking things. They are unstable and may be removed in future Cargo
versions, or only usable on nightly.
...
Use Case 5: Display help for a specific unstable nightly-only flag
Code:
cargo help -Z build-std
Motivation:
This use case is beneficial when you want to explore specific unstable nightly-only flags. It helps you understand how to use and experiment with these flags in your Rust projects.
Explanation:
By appending the specific flag after -Z, cargo help -Z flag provides detailed information about that flag. It includes a description, usage syntax, additional information, and examples.
Example Output:
build-std Build documentation for the standard library
This flag only accepts the value `std`. If supplied, the flag causes the
nightly documentation to be built with the standard library included in
the search path. If no libraries are present, the build will fail.
...
Use Case 6: Display help for specific topics using --explain
Code:
cargo help --explain authoring_dependencies
Motivation:
This use case is useful when you encounter an error or warning during the build process and want more information about it. It allows you to get detailed explanations about various topics related to building and managing dependencies.
Explanation:
By using the --explain flag followed by the specific topic, cargo help --explain topic provides detailed explanations for that topic. It helps you understand the concept, common issues, and how to resolve them.
Example Output:
Explainations for high-level options:
`dependencies` vs `dev-dependencies` vs `build-dependencies`
Each package in Cargo has three kinds of dependencies: dependencies,
development dependencies, and build dependencies.
Dependencies are used by your package in all modes (e.g., for building and
running). Development dependencies are used only for development and are not
included in packages made for other people to depend upon. Build dependencies
are only used for compiling (i.e., the `build` command) but aren't used to
compile the main crate itself. They're used for tasks like running build
scripts or proc macro crates incrementally, while the main crate itself
is being compiled.
...
Use Case 7: Display help for a specific subcommand’s combination of options
Code:
cargo help run --example
Motivation:
This use case helps when you want to build and execute a specific example from your Rust project. It provides information about how to use the run subcommand in combination with the --example option.
Explanation:
By appending the desired combination of options, cargo help subcommand --option displays detailed information about how to use that particular combination. It explains the usage syntax and provides additional examples.
Example Output:
run - Build and execute a single example
Usage: cargo run --example EXAMPLE_NAME [OPTIONS]
Options:
-h, --help Print this message and exit
-p, --package PACKAGE_NAME Build the specified package, including its dependencies.
--release Build artifacts in release mode, with optimizations
This will compile the specified example of the package using any necessary
dependencies and run it. The EXAMPLE_NAME argument is the name of the example
to run.
The `--example` option can be used to specify the example by name directly.
...
Use Case 8: Display help for a specific package within a workspace
Code:
cargo help test -p my-crate
Motivation:
This use case is helpful when your Rust project is organized as a workspace with multiple packages, each having its own tests. It provides detailed information about running tests for a specific package within the workspace.
Explanation:
By using the -p or --package option followed by the package name, cargo help subcommand --option package_name displays detailed information about running tests specifically for that package.
Example Output:
test - Execute all tests of a package
Usage: cargo test [OPTIONS]
Options:
-h, --help Print this message and exit
--manifest-path PATH Path to the manifest to compile
-p, --package PACKAGE_NAME Test only this package's library
--doc Build only this documentation test (if the package has documentation tests)
...
--release Build artifacts in release mode, with optimizations
--package-name Build this package's unit tests
...
If the `--package` argument is given, then SPEC is a package id specification
which indicates which package should be tested. If it is not given, then all
packages in the workspace are tested.
...
Conclusion
The cargo help command is a powerful tool for understanding the different functionalities and options available in Cargo. By exploring these various use cases, you can become more proficient in utilizing Cargo to manage and build your Rust projects efficiently.
Remember, whenever you need assistance or detailed information about Cargo or any of its subcommands, cargo help is only a command away!
