bash-mcp

A simple MCP (Model Context Protocol) server that enables Claude to execute shell commands without permission prompts.

⚠️ Security Warning: This server executes arbitrary shell commands. Use with caution and only in trusted environments.

Installation

# Install globally
npm install -g bash-mcp

# Or use with npx
npx bash-mcp

Quick Start

For Claude Desktop

Add to your claude_desktop_config.json:

{
  "mcpServers": {
    "bash": {
      "command": "npx",
      "args": ["bash-mcp"]
    }
  }
}

For Claude Code (Cursor, VS Code)

1. Open command palette (Cmd/Ctrl + Shift + P)
2. Run "MCP: Add Server"
3. Select "NPM" as the server type
4. Enter: bash-mcp

Available Tools

run - Execute a command

// Simple command
run("ls -la")

// With working directory
run("npm test", { cwd: "/path/to/project" })

// With timeout (milliseconds)
run("long-running-command", { timeout: 60000 })

run_background - Start a background process

// Start a dev server
run_background("npm run dev", "frontend")

// Start backend service with working directory
run_background("./gradlew bootRun", "backend", { cwd: "./backend" })

kill_background - Stop a background process

kill_background("frontend")

list_background - List all background processes

list_background()

Example Usage

User: Start the development servers
Assistant: I'll start both frontend and backend servers for you.

[Uses run_background tool]
Started frontend server (PID: 12345)
Started backend server (PID: 12346)

User: Check if they're running
Assistant: [Uses list_background tool]
Both servers are running successfully!

Response Format

All tools return JSON formatted responses:

{
  "success": true,
  "stdout": "command output",
  "stderr": "error output if any",
  "command": "executed command"
}

For background processes:

{
  "success": true,
  "name": "frontend",
  "pid": 12345,
  "command": "npm run dev",
  "message": "Started background process 'frontend' (PID: 12345)"
}

Features

• Execute any shell command without permission prompts
• Run long-running processes in the background
• Manage background processes (list, kill)
• Capture stdout and stderr
• Set working directory for commands
• Configure timeout for commands
• Automatic cleanup on server shutdown
• NEW: Automatic output truncation with full output saved to temp files
• NEW: Configurable output size limits and temp directory via environment variables

Environment Variables

• BASH_MCP_MAX_OUTPUT_SIZE: Maximum output size in bytes before truncation (default: 51200/50KB)
• BASH_MCP_TEMP_DIR: Directory for storing full output when truncated (default: system temp directory)

Example Configuration

{
  "mcpServers": {
    "bash": {
      "command": "npx",
      "args": ["bash-mcp"],
      "env": {
        "BASH_MCP_MAX_OUTPUT_SIZE": "102400",
        "BASH_MCP_TEMP_DIR": "/tmp/bash-mcp-outputs"
      }
    }
  }
}

Output Overflow Handling

When command output exceeds BASH_MCP_MAX_OUTPUT_SIZE:

1. Output is truncated to the specified limit
2. Full output is saved to a temporary file
3. The response includes the file path where full output can be found
4. If custom temp directory fails, falls back to system temp directory

Security Considerations

This MCP server executes arbitrary shell commands with the same privileges as the Node.js process. Only use in development environments or trusted contexts.

Requirements

• Node.js >= 16.0.0
• npm or npx

License

MIT

Author

tinywind [email protected]

Contributing

Issues and pull requests are welcome at GitHub.