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.

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

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:

Installing run is straightforward. Choose the method that works best for your system:

# 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

curl -LO https://github.com/Esubaalew/run/releases/latest/download/run-deb.sha256
DEB_FILE=$(awk '{print $2}' run-deb.sha256)
curl -LO "https://github.com/Esubaalew/run/releases/latest/download/${DEB_FILE}"
sha256sum --check run-deb.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           # optional: append ~/.local/bin to PATH

Verify installation:

# Verify installation
run --version

Output:

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+ languages:

run supports 25 programming languages out of the box, covering a wide range of paradigms and use cases:

# Scripting Languages
Python, JavaScript, Ruby, Bash, Lua, Perl, PHP

# Compiled Languages
Rust, Go, C, C++, Java, C#, Swift, Kotlin, Crystal, Zig, Nim

# Typed & Functional Languages
TypeScript, Haskell, Elixir, Julia

# Specialized Languages
R (Statistical computing)
Dart (Mobile development)

Categorization notes

The categories above are usage-based to match how you’ll likely run code with run rather than strict language taxonomies. Examples:

• Kotlin can target the JVM, Native, or JavaScript. If you’re using Kotlin/JS, it behaves closer to the “Web & typed scripting” workflow, while Kotlin/JVM fits “Systems & compiled” (with a JRE).
• Swift is listed under “Systems & compiled” because swiftc produces native binaries; however, you can still use it interactively via run for scripting-like workflows.
• TypeScript typically runs via Node or Deno at runtime (transpiled), which is why it appears under “Web & typed scripting.”

These groupings optimize for how commands are invoked and which toolchains run detects and orchestrates.

Complete Language Aliases Reference

Every language in run has multiple aliases for convenience. Use whichever feels most natural to you:

Command Variations - Flexible Syntax

run supports multiple command formats to fit your workflow. You can be explicit with --lang or let run auto-detect the language:

1. Full syntax with --lang and --code

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

Output:

2. Shorthand flags (-l for --lang, -c for --code)

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

3. Omit --code flag (auto-detected)

run --code "fn main() { println!(\"hello from rust\"); }"

Output:

4. Shorthand - just the code

run "fn main() { println!(\"hello from rust\"); }"

Output:

5. Language first, then code

run rust "fn main() { println!(\"hello from rust\"); }"

Output:

Command-Line Flags Reference

run provides both long-form and short-form flags for convenience:

# Language specification
--lang, -l          Specify the programming language
run --lang python "print('hello')"
run -l python "print('hello')"

# Code input
--code, -c          Provide code as a string
run --code "print('hello')"
run -c "print('hello')"

# Combined usage
run -l python -c "print('hello')"
run --lang python --code "print('hello')"

⚠️ When to Use --lang (Important!)

While run can auto-detect languages, ambiguous syntax can cause confusion. For example, print('hello') looks similar in Python, Ruby, Lua, and other languages. Always use --lang for correctness when the syntax is ambiguous or when you need deterministic behavior.

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

Output:

hello  # But which language was used?

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

Output:

hello  # Guaranteed to use Python

RECOMMENDATION: Always use --lang for correctness when:

• The syntax is ambiguous across multiple languages

• You want to ensure the exact language is used

• You're writing scripts or automation that must be deterministic

Main Function Flexibility

For compiled languages (Rust, Go, C, C++, Java, etc.), run is smart about main functions:

• Write complete programs with main functions

• Write code without main functions (run wraps it automatically)

• Both approaches work in REPL mode and inline execution

Go Example - With main function

$ run go
run universal REPL. Type :help for commands.

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

Go Example - Without main function

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

Examples

Real programs live under the examples/ tree—each language has a hello and a progress scenario. The headers document expected output so you can diff your toolchain.

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

REPL

Being inside REPL we can use the ff commands

The REPL supports several built-in commands for managing your session:

Interactive REPL - Line by Line or Paste All

The REPL mode is incredibly flexible. You can:

• Type code line by line interactively

• Paste entire programs at once

• Mix both approaches in the same session

This works for ALL supported languages!

Python Example - Paste entire program

$ 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)}")
F(0) = 0
F(1) = 1
F(2) = 1
F(3) = 2
F(4) = 3
F(5) = 5
F(6) = 8
F(7) = 13
F(8) = 21
F(9) = 34

Python Example - Line by line

python>>> x = 10
python>>> y = 20
python>>> print(x + y)
30

Variable Persistence & Language Switching

Variables persist across REPL commands within the same session. You can also switch languages on the fly using the :lang command (e.g., :c, :py, :go):

In REPL mode, variables persist across commands within the same language session. You can also switch languages on the fly using :lang commands.

When you switch languages, variables from the previous language do NOT carry over (each language has its own isolated session).

Variable Persistence Example

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

go>>> :c
switched to c

c>>> int x = 10;
c>>> x
10
c>>> 10 + 10
20

c>>> :py
switched to python

python>>> y = 10
python>>> y
10
python>>> print(y)
10
python>>> z = 4
python>>> z is y
False
python>>> z == y
False

Language Switching Commands

Switch between languages instantly in REPL mode using colon commands

Built-in REPL Commands

:help              → Show help and available commands
:languages         → List all supported languages
:clear             → Clear the screen
:exit or :quit     → Exit the REPL
:lang <language>   → Switch to a different language
Ctrl+D             → Exit the REPL

Stdin Piping Examples

run supports piping input from stdin to your code snippets across all languages. Here are more examples for different languages:

Node.js (JSON Processing)

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

Output:

Python (Uppercase Conversion)

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

Output:

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())'

Output:

Ruby (Line Counting)

echo -e "line1\nline2\nline3" | run ruby --code "puts gets(nil).lines.count"

Output:

Bash (Echo with Prefix)

echo "input text" | run bash --code 'read line; echo "Processed: $line"'

Output:

Language-Specific Notes

For detailed usage, quirks, and best practices for each language, visit the dedicated documentation:

• Python: Tips for scripting, data processing, and REPL persistence.
• JavaScript/Node.js: Async code, modules, and stdin handling.
• Rust: Compilation flags, error handling, and workspace management.
• Go: Package imports, build optimizations, and concurrency examples.
• C/C++: Compiler selection, linking, and multi-file support.
• Java: Classpath management, JVM args, and enterprise patterns.
• TypeScript: Type checking, Deno vs Node, and transpilation.
• And more... for all 25+ languages including Ruby, PHP, Haskell, Elixir, and specialized ones like R and Julia.

Each language doc covers:

• Toolchain requirements and detection
• REPL-specific features (e.g., persistent state)
• Common pitfalls and workarounds
• Advanced examples (e.g., file I/O, networking)

License

Apache 2.0. See LICENSE for details.

Built with ❤️ in Rust. If run unblocks your workflow, star the repo and share it with other polyglot hackers.