brush-parser

brush (Bo(u)rn(e) RUsty SHell) is a POSIX- and bash-compatible shell, implemented in Rust. It's built and tested on Linux, macOS, and WSL. Native Windows support is experimental.

brush is functional for interactive use as a daily driver! It executes most sh and bash scripts we've encountered. Known limitations are tracked with filed issues. Out of an abundance of caution, we wouldn't recommend using it yet in production scenarios in case it doesn't behave identically to your existing stable shell. (If you do find any behavioral differences, though, please report them with an issue!)

Contributions and feedback of all kinds are welcome! For more guidance, please consult our contribution guidelines. For more technical details, please consult the documentation in this repo.

This project was originally borne out of curiosity and a desire to learn. We're doing our best to keep that attitude :).

📝 License

Available for use and distribution under the MIT license.

⌨️ Installation

When you run brush, it should look exactly as bash does on your system: it processes your .bashrc and other standard configuration. If you'd like to distinguish the look of brush from the other shells on your system, you may author a ~/.brushrc file.

gh release download --repo reubeno/brush --pattern "brush-x86_64-unknown-linux-gnu.*"

gh attestation verify brush-x86_64-unknown-linux-gnu.tar.gz --repo reubeno/brush

cargo binstall brush-shell

cargo install --locked brush-shell

nix run 'github:NixOS/nixpkgs/nixpkgs-unstable#brush' -- --version

pacman -S brush

brew install brush

👥 Community

brush has a community Discord server, available here.

🔍 Known limitations

There are some known gaps in compatibility. Most notably:

• Some set and shopt options. The set builtin is implemented, as is set -x and many frequently used set/shopt options, but a number aren't fully implemented. For example, set -e will execute but its semantics aren't applied across execution.

If you're interested, we'd love contributions to improve compatibility, broaden test coverage, or really any other opportunities you can find to help us make this project better.

🧪 Testing strategy

This project is primarily tested by comparing its behavior with other existing shells, leveraging the latter as test oracles. The integration tests implemented in this repo include 675+ test cases run on both this shell and an oracle, comparing standard output and exit codes.

For more details, please consult the reference documentation on integration testing.

🙏 Credits

There's a long list of OSS crates whose shoulders this project rests on. Notably, the following crates are directly relied on for major portions of shell functionality:

• reedline - for readline-like input and interactive usage
• clap - command-line parsing, used both by the top-level brush CLI as well as built-in commands
• fancy-regex - relied on for everything regex
• tokio - async, well, everything
• nix rust crate - higher-level APIs for Unix/POSIX system APIs

For testing, performance benchmarking, and other important engineering support, we use and love:

• pprof-rs - for sampling-based CPU profiling
• criterion.rs - for statistics-based benchmarking
• bash-completion - for its completion test suite and general completion support!

🔗 Links: other shell implementations

There are a number of other POSIX-ish shells implemented in a non-C/C++ implementation language. Some inspirational examples include:

• nushell - modern Rust-implemented shell (which also provides the reedline crate we use!)
• rusty_bash
• mvdan/sh
• Oils
• fish (as of 4.0)

We're sure there are plenty more; we're happy to include links to them as well.