Command-line interface for mruby/edge - a lightweight, WebAssembly-focused mruby VM implementation.

mruby/edge is an mruby-compatible virtual machine implementation written in Rust, specifically designed for WebAssembly environments. It aims to provide:

• WebAssembly-first design: Optimized for running Ruby code in browsers and edge computing environments
• Lightweight runtime: Minimal footprint and binary size suitable for constrained environments
• mruby compatibility: Executes mruby bytecode (.mrb files) and Ruby source code
• Rust safety: Built with Rust for memory safety and reliability

Install mrubyedge-cli using cargo:

cargo install mrubyedge-cli

Or build from source:

git clone https://github.com/mrubyedge/mrubyedge.git
cd mrubyedge
cargo build --release -p mrubyedge-cli

The binary will be available as mrbedge.

Create a simple Ruby script hello.rb:

puts "Hello from mruby/edge!"
puts RUBY_ENGINE

Run it with mrbedge:

mrbedge hello.rb
# or explicitly
mrbedge run hello.rb

The run subcommand executes Ruby source files (.rb) or compiled mruby bytecode (.mrb).

Usage:

mrbedge run <file>
# or simply
mrbedge <file>

Examples:

# Run Ruby source
mrbedge run script.rb

# Run compiled bytecode
mrbedge run script.mrb

Compiles Ruby source code into mruby bytecode format for faster loading and distribution.

Usage:

mrbedge compile-mrb <input.rb> -o <output.mrb>

Examples:

# Compile a single file
mrbedge compile-mrb app.rb -o app.mrb

# Run the compiled bytecode
mrbedge run app.mrb

Benefits:

• Faster startup time (no parsing overhead)
• Smaller distribution size
• Protection of source code

Compiles Ruby code directly into a standalone WebAssembly module that can run in browsers or any WebAssembly runtime.

Usage:

mrbedge wasm <input.rb> -o <output.wasm>

Examples:

# Generate WebAssembly module
mrbedge wasm app.rb -o app.wasm

# Use in browser or Node.js
# The generated WASM can be loaded and executed in any WASM runtime

Use Cases:

• Serverless edge computing
• Browser-based applications
• Microservices with minimal overhead
• Cross-platform portable executables

The wasm command can generate both WASI-enabled and non-WASI WebAssembly binaries. By default, it produces WASI-enabled modules. To disable WASI support, use the --no-wasi flag.

• WASI-enabled: Supports file system access, environment variables, and standard I/O
• Non-WASI: Minimal pure WebAssembly suitable for browser environments with custom imports

You can specify WebAssembly function imports and exports using RBS (Ruby Signature) files. Place RBS files with specific naming conventions alongside your Ruby script:

For a Ruby script named foo.rb:

• foo.import.rbs: Defines external functions to import from the WebAssembly host
• foo.export.rbs: Defines Ruby functions to export as WebAssembly functions

Example:

# app.rb
def calculate(x, y)
  x + y
end

# app.export.rbs
def calculate: (Integer, Integer) -> Integer

# app.import.rbs
def external_log: (String) -> void

The generated WebAssembly module will expose calculate and can call external_log from the host environment.

Note: Inline RBS annotations for imports and exports will be supported in future releases.

• GitHub Repository
• API Documentation
• Core VM Documentation

See the LICENSE file in the repository root.