Code Runner

Run code snippets in 30+ programming languages including JavaScript, Python, TypeScript, Java, C, C++, Go, Rust, Ruby, PHP, and more. Use when the user wants to execute code, test algorithms, verify output, run scripts, or check code behavior. Supports both interpreted and compiled languages.

Code Runner Skill

This skill enables you to run code snippets in multiple programming languages directly from the command line.

When to Use This Skill

Use this skill when:

• The user wants to run or execute a code snippet
• Testing algorithm implementations or logic
• Verifying expected output of code
• Running quick scripts or one-liners
• Checking syntax or runtime behavior
• Demonstrating code functionality

Supported Languages

The following languages are supported (requires the interpreter/compiler to be installed):

Language	Command	File Extension
JavaScript	node	.js
TypeScript	ts-node	.ts
Python	python	.py
Java	java (compile & run)	.java
C	gcc (compile & run)	.c
C++	g++ (compile & run)	.cpp
Go	go run	.go
Rust	rustc (compile & run)	.rs
Ruby	ruby	.rb
PHP	php	.php
Perl	perl	.pl
Lua	lua	.lua
R	Rscript	.r
Swift	swift	.swift
Kotlin	kotlin	.kts
Scala	scala	.scala
Groovy	groovy	.groovy
Dart	dart	.dart
Julia	julia	.jl
Haskell	runhaskell	.hs
Clojure	clojure	.clj
F#	dotnet fsi	.fsx
C#	dotnet script	.csx
PowerShell	pwsh	.ps1
Bash	bash	.sh
Batch	cmd /c	.bat
CoffeeScript	coffee	.coffee
Crystal	crystal	.cr
Elixir	elixir	.exs
Nim	nim compile --run	.nim
OCaml	ocaml	.ml
Racket	racket	.rkt
Scheme	scheme	.scm
Lisp	sbcl --script	.lisp

See references/LANGUAGES.md for detailed language configuration.

How to Run Code

Step 1: Identify the Language

Determine the programming language from:

• User's explicit request (e.g., "run this Python code")
• File extension if provided
• Code syntax patterns

Step 2: Execute Using the Runner Script

⚠️ Important for AI Agents: Use stdin to avoid escaping issues with quotes, backslashes, and special characters.

Recommended Method (stdin):

bash

echo "<code>" | node scripts/run-code.cjs <languageId>

Alternative Method (CLI argument - for simple code only):

bash

node scripts/run-code.cjs <languageId> "<code>"

Example - JavaScript:

bash

echo "console.log('Hello, World!')" | node scripts/run-code.cjs javascript

Example - Python:

bash

echo "print('Hello, World!')" | node scripts/run-code.cjs python

Example - Java (multi-line):

bash

echo "public class Test {
    public static void main(String[] args) {
        System.out.println(\"Hello from Java!\");
    }
}" | node scripts/run-code.cjs java

Example - Multi-line code from variable:

bash

# In bash
CODE='import math
print("Pi:", math.pi)
print("Result:", math.factorial(5))'
echo "$CODE" | node scripts/run-code.cjs python

# In PowerShell (inline here-string)
@"
import math
print("Pi:", math.pi)
print("Result:", math.factorial(5))
"@ | node scripts/run-code.cjs python

Step 3: Return Results

• Show the output (stdout) to the user
• If there are errors (stderr), explain what went wrong
• Suggest fixes for common errors

Platform Notes

Windows

• Use cmd /c for batch scripts
• PowerShell scripts require pwsh or powershell
• Path separators use backslash \

macOS / Linux

• Bash scripts work natively
• Swift available on macOS
• Use #!/usr/bin/env shebang for portable scripts

Error Handling

Common issues and solutions:

1. Command not found: The language interpreter is not installed or not in PATH

   • Suggest installing the required runtime
   • Provide installation instructions

2. Syntax errors: Code has syntax issues

   • Show the error message
   • Point to the line number if available

3. Runtime errors: Code runs but fails during execution

   • Display the stack trace
   • Explain the error type

4. Timeout: Code takes too long (default: 30 seconds)

   • Warn about infinite loops
   • Suggest optimizations

Security Considerations

⚠️ Important: Running arbitrary code can be dangerous. Always:

1. Review the code before execution
2. Be cautious with code that:
   • Accesses the file system
   • Makes network requests
   • Executes system commands
   • Modifies environment variables
3. Consider running in a sandboxed environment for untrusted code

Examples

Example 1: Run a JavaScript calculation

bash

echo "console.log(Array.from({length: 10}, (_, i) => i * i))" | node scripts/run-code.cjs javascript

Output: [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

Example 2: Run Python with imports

bash

echo "import math; print(math.factorial(10))" | node scripts/run-code.cjs python

Output: 3628800

Example 3: Test a Go function

bash

echo 'package main; import "fmt"; func main() { fmt.Println("Hello from Go!") }' | node scripts/run-code.cjs go

Output: Hello from Go!