cargo-e

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e is for Example. cargo-e is a Cargo subcommand for running and exploring examples, binaries, and source code in Rust projects. Unlike cargo run --example, it executes the example directly if only one exists.

Most Important Features

• Runs a single example automatically when only one example is defined.
• Supports examples in different locations (bins, workspaces, etc.), detects tauri, dioxus, and leptos projects/examples.
• cargo-e as an Example:
  cargo-e itself serves as a practical example of an attempt to write a well-managed Rust project. It adopts conventional commits and adheres to SemVer. The project leverages GitHub Actions to automate releases, generate a CHANGELOG, and handle versioning via release-plz. As a learning vehicle for its creator, cargo-e also provides a model for others interested in effective coding and project management practices.

Quick Start

  cargo install cargo-e
  cd cool_examples
  cargo e

Overview

cargo-e makes it easy to run and explore sample code from your Rust projects. Whether you are working with built-in examples, extended samples, or binaries, cargo-e provides a unified interface to quickly launch your code, inspect its structure, and integrate with editors/tools.

Features

• runs the default example if there is only one example defined.
• ai summarization: info or 'i' sends the example code for summarization; including a YES or NO answer on if the code is safe to run. Interactive follow up questions may be asked to allow for concept/code exploration.
• partial search for matching: If an explicit name isn't found, a case-insensitive partial search is performed to list matching targets for user selection. one command for binaries and examples.
• rust-script/scriptisto: If an explicit name is a file, the first line is checked for a valid bang # rust-script/scriptisto. cargo e runs your scripts and is less typing.
• framework sample support: detects tauri, dioxus, leptos projects; running the target calls the associated framework runner.
• seamless sample execution: Run built-in examples and extended samples (located in the examples directory) with a simple command. Improved discoverability of examples and binaries, even across workspaces.
• automatic required feature detection: Examples and binaries marked with required features will automatically have those features applied. cargo-e takes care of that hassle for you.
• complete view of all targets: Not just for binaries and examples. Tests and bench targets too.
• interactive terminal UI (TUI): Optionally launch a feature-rich, interactive interface for browsing and selecting targets. (-t option)
• vscode integration: Jump directly into your source code and navigate to the fn main entry point automatically. ('e' key in TUI)
• bacon integration: Run bacon on your project/example. ('b' key in TUI)
• workspace integration: Automatically detects and uses workspace manifests for multi-crate projects. (-w option)
• configurable behavior: – Optional equivalent mode – cargo-e can behave identically to cargo run --example with bare minimum dependency
• cargo and target stderr and stdout filtering: -f sends all output from cargo and the target through a filter to determine accurate timing when --run-all is specified. cargo warnings and errors are rewritten to be more concise, numbered, and timed format. Errors are written in realtime and a table of errors is displayed conviently at the end of output, file references are all absolute and fully specified so your ctrl+clicks take you there. If you require a terminal, don't use -f, and your output will be unfiltered.
• subcommands: you may find that you like the rewritten cargo output and the additional detail provided in -f filtering. Specify a -s subcommand to run a subcommand other than the default run that cargo-e uses normally.

Introduction

When using cargo run --example in a project with a single example, Cargo does not execute the example. Instead of running the obvious example, it displays that there is one example available. This behavior differs from that of cargo run, which automatically runs the default build target without requiring additional arguments.

If you read cargo --help, you'll notice short keys such as r for run and b for build. cargo-e fills the e gap by serving as a dedicated tool for examples. It functions similarly to cargo run --example; it takes the example name and passes arguments just like --example, but with the added benefit that it will automatically run the single example if that is the only one defined.

Running the single example if there is only one example defined is a primary feature of cargo-e; it's what brought about this project. --example and --bin are often parsed, so changing Cargo's behavior is out of the question. In fact, this tool relies upon --example returning the list of examples instead of running the single example.

Projects organize examples in different ways – some using binaries, others placing them in an examples directory – cargo-e helps navigate and execute targets across diverse structures. Whether your project uses bins, examples, or even workspace configurations, cargo-e unifies these scenarios and simplifies the process of running and exploring your sample code.

Installation

Install cargo-e via Cargo:

cargo install cargo-e

Install cargo-e via git:

git clone https://github.com/davehorner/cargo-e 
cd cargo-e
cargo install --path .

Usage

Run an example directly from your project:

cargo e [OPTIONS] [EXAMPLE] [-- extra arguments]

If there is only one example, it will run that example, did I mention that already?

Command-line Options

• -t, --tui
  Launch the interactive terminal UI for selecting an example or binary.

• -w, --workspace
  Use the workspace manifest (the root Cargo.toml of your workspace) instead of the current directory.

• -W, --wait <seconds>
  Specify how many seconds to wait after the target process finishes so you can view its output.

Examples

• Run a specific example:

  cargo e my_example -- --flag1 value1
  

• Launch the TUI:

  cargo e --tui
  

• Use workspace mode:

  cargo e --workspace
  

• Partial Searches

  cargo e wgpu
  builtin: rust/nannou/Cargo.toml
  0 built-in examples (213 alternatives: 208 examples, 5 binaries).
  error: 0 named 'wgpu' found in examples or binaries.
  partial search results for 'wgpu':
    1: [ex.] wgpu_compute_shader
    2: [ex.] wgpu_image
    3: [ex.] wgpu_image_sequence
    4: [ex.] wgpu_instancing
    5: [ex.] wgpu_teapot
    6: [ex.] wgpu_teapot_camera
    7: [ex.] wgpu_triangle
    8: [ex.] wgpu_triangle_raw_frame
  * == # to run, tui, e<#> edit, 'q' to quit (waiting 5 seconds)
  

• Run All

  Execute all discovered examples or binaries in your project in a single run. Use a partial search to run only those matching targets.

  cargo e --run-all --quiet --release [partial_search_term]
  

  --run-all by itself (without a numeric value)

  will set the run mode to "forever"—meaning each target is allowed to run until it terminates naturally.

  --run-all 10

  means that each target will be run for 10 seconds. After 10 seconds, Cargo-e will prompt for a key press; if no key is pressed (or if a non-quit key is pressed), the running process will be killed, and the next target is started.

Displays detailed help information. Use the -h option for additional details on all available flags.

Features and Configuration

cargo-e leverages Cargo's feature flags to provide fine-grained control over the included components and dependencies. Using conditional compilation whenever possible, the dependency tree remains lean by including only what is necessary.

• Default Features:
  Building cargo-e without specifying additional features enables the tui and concurrent features by default. Terminal UI support is provided via crossterm and ratatui, while concurrency support is offered through threadpool.

• Optional and Platform-Specific Features:

  • windows: Includes Windows-specific dependencies to enhance compatibility on Windows systems and to limit unneeded energy, time, space on bloat.
  • equivalent: Functions as an alias/shortcut for --example without enabling extra features.

• Customizing the Build:
  Default features may be disabled using --no-default-features, and desired features can be enabled using --features. For example:

  cargo build --no-default-features --features tui
  

Want to stop the version check prompts and queries?

By default, cargo-e bundles the e_crate_version_checker crate through the "check-version" feature. This means that when you run cargo-e, it performs a version check on startup and prompts you if a newer version is available. This helps keep you informed about the latest and greatest, but it also serves as a safeguard to prevent legacy builds from being used inadvertently. It may feel intrusive or annoying for some.

If you prefer to avoid that automatic version check, additional output, delay, and process, you can disable the default features during installation and then re-enable only the ones you want (like "tui", "concurrent", "funny-docs", "uses_reqwest", and "uses_serde"). Use the following command:

cargo install cargo-e --no-default-features --features "tui concurrent funny-docs uses_reqwest uses_serde"

This command installs cargo-e without the "check-version" feature, ensuring that no version check or upgrade prompt occurs at runtime. The funny-docs are a joke to be filled in. The joke is that a user would actually open rust docs --open and read the funny or find a guide worth reading. It is the default docs. Did you read the guide?

Note: Disabling the version check means you forgo a mechanism designed to ensure that you’re not using less desirable builds.

Work Arounds for Cargo

• workspace package believes it's in a workspace when it's not

  • auto-resolve-workspace-errors.md

Prior Art and Alternative Approaches

Several tools and techniques have been developed to ease the exploration and execution of example code in Rust projects:

• Built-in Cargo Support:

  Cargo provides support for running examples with the cargo run --example command. However, this approach places the example at the level of an option, requiring users to type out a longer command—at least 19 characters per invocation—and, in many cases, two separate invocations (one for seeing and another to actually do). This extra keystroke overhead can make the process less efficient for quick experimentation.

• cargo-examples:

  The cargo-examples project offers another approach to handling examples in Rust projects. It focuses on running all the examples in alphabetical order with options to start from a point in the list. Simplifying the execution of example code, demonstrating a similar intent to cargo-e by reducing the overhead of managing example invocations.

  It handles various example structures:

  • Single-file examples: Located directly as <project>/examples/foo.rs

  • Multi-file examples: Structured as <project>/examples/bar/main.rs

  • Manifest-based examples: Defined in Cargo.toml using the [[example]] configuration

  • Subproject examples: Examples in subdirectories containing their own Cargo.toml, which standard Cargo commands cannot run out-of-the-box.

  • Efficient Execution:
    Examples are run in alphabetical order, and the tool provides options such as --from to start execution at a specific example. This reduces the need for multiple long invocations and simplifies the workflow.

• cargo-play:

  The cargo-play tool is designed to run Rust code files without the need to manually set up a Cargo project, streamlining rapid prototyping and experimentation.

The Wild West of Code Organization

Many developers create their own custom scripts or tools to expose examples and binaries, leading to several issues:

• Inconsistency Across Projects: Each project tends to have its own unique implementation. This inconsistency means that even though some crates offer excellent examples, these examples are often hidden or not uniformly accessible to users.
• Hidden Valuable Examples: Custom solutions may showcase wonderful, context-specific examples, but their lack of standardization makes them difficult to discover without prior knowledge of the project’s internal tooling.
• Extra Compilation and Maintenance Effort: These ad-hoc methods usually require additional effort to compile and manage. The time spent on maintaining such tools often exceeds their practical benefits.
• Safety Concerns When Executing Code: Custom scripts may have hard-coded paths, exceptional test cases, or other assumptions specific to a developer’s environment. As a result, running every test, binary, or example without careful vetting can introduce risks. The lack of uniform safety checks means that it's not always safe to execute all available code without considering these potential pitfalls.

While a unified tool like cargo-e may not eliminate every security concern, it mitigates some risks by providing a more predictable and consistent interface for running other people's code (OPC). This helps developers avoid the common pitfalls associated with individually maintained scripts and ad-hoc solutions.

Keep your Zoo out of our Namespace

• src - manage your personal zoo of repositories.
• rg - you don't want this crate

These two crates are ridiculous and deserve special mention - as of 2025-03-10.

• src has 27,876 downloads.
• rg has 13,369 downloads.

This is the stuff that makes cargo rust a dangerous place to play and I do not recommend blindly running every crate's fn main. Both src and rg have gotten me. Another time when I mistakenly installed something, the crate told me to take a long walk in so many words. report or complain; be thankful you still own your hardware and data, but that's 40K people who are being exposed to a Zoo. It's reason enough to not leave cargo enabled by default. I'll type cargo when I mean to type git. 27,876 downloads in five years.

A name for a common src folder or rust based program and walk away. I don't know that it's squatting; its worse than that. src has 7 versions. rg 3.

this, coming from someone trying to define the short 'e' cargo subcommand.

nvm the the short code zOoo. not everything is an example. watch those fingers.

Not a Digital Junk Drawer

Crates can easily become digital junk drawers—random directories and executables thrown around like confetti. When developers adopt the "stick it anywhere" with no annotation/metadata, the result is a cluttered mess of custom scripts and ad-hoc tools that expose testers systems to risk by just running everything.

Embracing Cargo’s Convention

When you bypass Cargo’s metadata-driven approach by using custom, ad-hoc methods, you lose the inherent benefits that come from a well-defined project structure that follow some convention. Cargo.toml encapsulates critical metadata—like dependency management, versioning, and build instructions—that ensures consistency and predictability across Rust projects.

Contributing

Contributions are welcome! If you have suggestions or improvements, feel free to open an issue or submit a pull request.

License

This project is dual-licensed under the MIT License or the Apache License (Version 2.0), at your option.

Acknowledgements

• Built with the power of the Rust ecosystem and libraries like clap, crossterm (optional), and ratatui (optional).
• Special thanks to the Rust community and all contributors for their continued support.

You are reading documentation version 0.2.17. If this does not match the version displayed above, then you're not reading the latest documentation.

Addendum

• documents/1_Cool_Examples_With_Cargo_e.md

• HORNER EXAMPLE 1: examples/funny_examples.rs

• HORNER EXAMPLE 2: addendum/e_crate_version_checker/src/main.rs

• HORNER EXAMPLE 3: addenda/e_update_readme/src/bin/e_update_readme.rs