run

Polyglot command runner & smart REPL that lets you script, compile, and iterate in 25+ languages without touching another CLI.

Website • Docs Overview

Built in Rust for developers who live in multiple runtimes. run gives you a consistent CLI, persistent REPLs, and batteries-included examples for your favorite languages.

What's New in 0.10

• Custom language aliases — run alias add, run alias remove, persisted in ~/.config/run-kit/aliases.toml. See the aliases docs.
• run fmt / run share now detect all 25 languages by file extension (Kotlin, Swift, Dart, etc.), not just a subset.
• Run 2.0 CI — v2 feature builds and tests run in GitHub Actions.
• WASI target alignment — wasm32-wasip1 used consistently across build, deploy, and registry metadata.
• Toolchain lockfile — run.lock.toml placeholder hashes removed; run run v2 toolchain sync to populate.

What's New in 0.9

• Toolchain-aware blake3 build cache under the platform cache directory with run cache --stats and run cache --clear.
• New workflow commands: run doctor, run fmt <file>, run snippet <lang> <name>, run watch <file>, and run share <file>.
• Scriptable execution via --json and predictable timeout behavior via --timeout <seconds> with exit code 124.
• Per-language REPL history, safer reset behavior, and hardened child-process shutdown.
• C++ precompiled-header cache invalidation now tracks the exact compiler identity, so Clang/Xcode upgrades no longer poison inline, stdin, or REPL runs.
• run --help now lists all workflow subcommands directly.

Run 2.0 (Experimental)

Run 2.0 adds WASI 0.2 component support for cross-language composition, instant startup, and edge deployment.

run v2 --help

Quick Links:

• Run 2.0 Examples
• Migration Guide
• Registry Server

See Run 2.0 Documentation below for details.

Website and Docs

The official website and full documentation are available here:

• Website: https://run.esubalew.et/
• Docs Overview: https://run.esubalew.et/docs/overview
• Docs source: https://github.com/esubaalew/run-docs

Use these links to explore features, language guides, and detailed examples.

Overview - Universal Multi-Language Runner

A powerful command-line tool for executing code in 25 programming languages

What is run?

run is a universal multi-language runner and smart REPL (Read-Eval-Print Loop) written in Rust. It provides a unified interface for executing code across 25 programming languages without the hassle of managing multiple compilers, interpreters, or build tools.

Whether you're a beginner learning your first programming language or an experienced polyglot developer, run streamlines your workflow by providing consistent commands and behavior across all supported languages.

Who is this for?

• Beginners: Learn programming without worrying about complex setup procedures. Just install run and start coding in any language.
• Students: Quickly test code snippets and experiment with different programming paradigms across multiple languages.
• Developers: Prototype ideas rapidly, test algorithms, and switch between languages seamlessly without context switching.
• DevOps Engineers: Write and test automation scripts in various languages from a single tool.
• Educators: Teach programming concepts across multiple languages with a consistent interface.

Why was run created?

Traditional development workflows require installing and configuring separate tools for each programming language. This creates several problems:

• Time-consuming setup: Installing compilers, interpreters, package managers, and configuring environments for each language.
• Inconsistent interfaces: Each language has different commands and flags for compilation and execution.
• Cognitive overhead: Remembering different commands and workflows for each language.
• Barrier to entry: Beginners struggle with setup before writing their first line of code.

run solves these problems by providing a single, unified interface that handles all the complexity behind the scenes. You focus on writing code, and run takes care of the rest.

Why Rust?

run is built with Rust for several compelling reasons:

• Performance: Rust's zero-cost abstractions and efficient memory management ensure run starts instantly and executes with minimal overhead.
• Reliability: Rust's strong type system and ownership model prevent common bugs like null pointer dereferences and data races, making run stable and crash-resistant.
• Cross-platform: Rust compiles to native code for Windows, macOS, and Linux, providing consistent behavior across all platforms.
• Memory safety: No garbage collector means predictable performance without unexpected pauses.
• Modern tooling: Cargo (Rust's package manager) makes building and distributing run straightforward.
• Future-proof: Rust's growing ecosystem and industry adoption ensure long-term maintainability.

Quickstart

# Show build metadata for the current binary
run --version

# Execute a snippet explicitly
run --lang python --code "print('hello, polyglot world!')"

# Let run detect language from the file extension
run examples/go/hello/main.go

# Drop into the interactive REPL (type :help inside)
run

# Pipe stdin (here: JSON) into Node.js
echo '{"name":"Ada"}' | run js --code "const data = JSON.parse(require('fs').readFileSync(0, 'utf8')); console.log(\`hi \${data.name}\`)"

# Pipe stdin into Python
echo "Hello from stdin" | run python --code "import sys; print(sys.stdin.read().strip().upper())"

# Pipe stdin into Go
echo "world" | run go --code 'import "fmt"; import "bufio"; import "os"; scanner := bufio.NewScanner(os.Stdin); scanner.Scan(); fmt.Printf("Hello, %s!\n", scanner.Text())'

Installation

All release assets are published on the GitHub Releases page, including macOS builds for both Apple Silicon (arm64) and Intel (x86_64). Pick the method that fits your platform:

cargo install run-kit

# Or build from source
git clone https://github.com/Esubaalew/run.git
cd run
cargo install --path .

brew install --formula https://github.com/Esubaalew/run/releases/latest/download/homebrew-run.rb

ARCH=${ARCH:-amd64}
DEB_FILE=$(curl -s https://api.github.com/repos/Esubaalew/run/releases/latest \
  | grep -oE "run_[0-9.]+_${ARCH}\\.deb" | head -n 1)
curl -LO "https://github.com/Esubaalew/run/releases/latest/download/${DEB_FILE}"
curl -LO "https://github.com/Esubaalew/run/releases/latest/download/${DEB_FILE}.sha256"
sha256sum --check "${DEB_FILE}.sha256"
sudo apt install "./${DEB_FILE}"

scoop install https://github.com/Esubaalew/run/releases/latest/download/run-scoop.json

curl -fsSLO https://raw.githubusercontent.com/Esubaalew/run/master/scripts/install.sh
chmod +x install.sh
./install.sh --add-path

Verify installation:

run --version

How it works

run shells out to real toolchains under the hood. Each LanguageEngine implements a small trait that knows how to:

1. Detect whether the toolchain is available (e.g. python3, go, rustc).
2. Prepare a temporary workspace (compilation for compiled languages, transient scripts for interpreters).
3. Execute snippets, files, or stdin streams and surface stdout/stderr consistently.
4. Manage session state for the interactive REPL (persistent modules, stateful scripts, or regenerated translation units).

This architecture keeps the core lightweight while making it easy to add new runtimes or swap implementations.

Supported languages

run supports 25 programming languages out of the box:

Complete Language Aliases Reference

Alias	Description	Badge
python, py, py3, python3	Python programming language
javascript, js, node, nodejs	JavaScript (Node.js runtime)
typescript, ts, ts-node, deno	TypeScript with type checking
rust, rs	Rust systems programming language
go, golang	Go programming language
c, gcc, clang	C programming language
cpp, c++, g++	C++ programming language
java	Java programming language
csharp, cs, dotnet	C# (.NET)
ruby, rb, irb	Ruby programming language
bash, sh, shell, zsh	Bash shell scripting
lua, luajit	Lua scripting language
perl, pl	Perl programming language
groovy, grv, groovysh	Groovy on the JVM
php, php-cli	PHP scripting language
haskell, hs, ghci	Haskell functional language
elixir, ex, exs, iex	Elixir functional language
julia, jl	Julia scientific computing
dart, dartlang, flutter	Dart language (Flutter)
swift, swiftlang	Swift programming language
kotlin, kt, kts	Kotlin (JVM/Native)
r, rscript, cran	R statistical computing
crystal, cr, crystal-lang	Crystal language
zig, ziglang	Zig systems language
nim, nimlang	Nim programming language

Command Variations - Flexible Syntax

run supports multiple command formats:

# Full syntax
run --lang rust --code "fn main() { println!(\"hello\"); }"

# Shorthand flags
run -l rust -c "fn main() { println!(\"hello\"); }"

# Language first, then code
run rust "fn main() { println!(\"hello\"); }"

# Auto-detect from file
run examples/rust/hello.rs

Command-Line Flags Reference

run -l python -c "print('hello')"
run --json python -c "print('hello')"
run snippet go goroutine-pool > pool.go
run watch examples/python/counter.py

When to Use --lang (Important!)

Always use --lang when syntax is ambiguous:

# Ambiguous - may choose wrong language
run "print('hello')"

# Explicit - always correct
run --lang python "print('hello')"

Main Function Flexibility

For compiled languages, run is smart about main functions:

$ run go
go>>> fmt.Println("Hello, world!")
Hello, world!

go>>> package main
import "fmt"
func main() { fmt.Println("Hello!") }
Hello!

Examples

Real programs live under the examples/ tree:

run examples/rust/hello.rs
run examples/typescript/progress.ts
run examples/python/counter.py

REPL

The REPL supports built-in commands:

Interactive REPL - Line by Line or Paste All

$ run python
python>>> def fibonacci(n):
    if n <= 1:
        return n
    return fibonacci(n-1) + fibonacci(n-2)

for i in range(10):
    print(f"F({i}) = {fibonacci(i)}")

Variable Persistence & Language Switching

$ run go
go>>> x := 10
go>>> x
10

go>>> :py
switched to python

python>>> y = 10
python>>> print(y)
10

Stdin Piping Examples

# Node.js (JSON Processing)
echo '{"name":"Ada"}' | run js --code "const data = JSON.parse(require('fs').readFileSync(0, 'utf8')); console.log(\`hi \${data.name}\`)"

# Python (Uppercase)
echo "Hello" | run python --code "import sys; print(sys.stdin.read().strip().upper())"

# Go (Greeting)
echo "world" | run go --code 'import "fmt"; import "bufio"; import "os"; scanner := bufio.NewScanner(os.Stdin); scanner.Scan(); fmt.Printf("Hello, %s!\n", scanner.Text())'

Language-Specific Notes

For detailed usage and best practices for each language, visit the documentation.

Run 2.0 - WASI Component Runtime

Run 2.0 is an experimental extension that adds WASI 0.2 component support. It is opt-in and does not replace Run 1.0.

What Run 2.0 Adds

• Cross-language composition: Rust, Python, Go, JS components calling each other via WIT interfaces
• Instant startup: <10ms cold start (vs Docker's 5-10 seconds)
• Hermetic builds: Reproducible builds with toolchain lockfiles
• Edge deployment: Deploy to Cloudflare Workers, AWS Lambda, Vercel

Quick Start

# Install with v2 support
cargo install run-kit --features v2

# See v2 commands
run v2 --help

# Initialize a project
run v2 init my-app
cd my-app

# Build and run
run v2 build
run v2 dev

Run 2.0 Commands

Publishing to the Registry

Run 2.0 publishes components via run v2 publish (alias for run v2 deploy --target registry).

Default registry:

• https://registry.esubalew.dev

Publish a component:

run v2 build
run v2 publish --token YOUR_TOKEN

Override the registry URL:

run v2 publish \
  --registry-url https://registry.esubalew.dev \
  --token YOUR_TOKEN

You can also set the token in run.toml:

[registry]
auth_token = "${RUN_AUTH_TOKEN}"

Keep tokens in environment variables and do not commit them to source control.

Configuration

run.toml defines your project:

[package]
name = "my-app"
version = "1.0.0"

[[component]]
name = "api"
source = "src/lib.rs"
language = "rust"
wit = "wit/api.wit"

[dev]
watch = ["src/**/*.rs"]
hot_reload = true

Resources

• Run 2.0 Examples - Working examples and templates
• Migration Guide - Migrate from Docker to Run 2.0
• Registry Server - Self-hosted component registry

License

Apache 2.0. See LICENSE for details.

Built with Rust. If run helps your workflow, star the repo and share it with other polyglot developers.