bash-tool

bash-tool

Generic bash tool for AI agents, compatible with AI SDK.

Installation

npm install bash-tool just-bash

For full VM support, install @vercel/sandbox or another sandbox product instead of just-bash.

Usage

import { createBashTool } from "bash-tool";
import { ToolLoopAgent, stepCountIs } from "ai";

const { tools } = await createBashTool({
  files: {
    "src/index.ts": "export const hello = 'world';",
    "package.json": '{"name": "my-project"}',
  },
});

const agent = new ToolLoopAgent({
  model: yourModel,
  tools,
  // Or use just the bash tool as tools: {bash: tools.bash}
  stopWhen: stepCountIs(20),
});

const result = await agent.generate({
  prompt: "Analyze the project and create a summary report",
});

Tools

The tools object contains three tools that can be used by AI agents:

bash

Execute bash commands in the sandbox environment. For analysis agents, this may be the only tool you need to give to the agent.

Input:

• command (string): The bash command to execute

Returns:

• stdout (string): Standard output from the command
• stderr (string): Standard error from the command
• exitCode (number): Exit code of the command

readFile

Read the contents of a file from the sandbox.

Input:

• path (string): The path to the file to read

Returns:

• content (string): The file contents

writeFile

Write content to a file in the sandbox. Creates parent directories if needed.

Input:

• path (string): The path where the file should be written
• content (string): The content to write to the file

Returns:

• success (boolean): true if the write succeeded

Advanced Usage

Upload a local directory

const { bash } = await createBashTool({
  uploadDirectory: {
    source: "./my-project",
    include: "**/*.{ts,json}", // optional glob filter
  },
});

Use @vercel/sandbox for full VM

import { Sandbox } from "@vercel/sandbox";

const sandbox = await Sandbox.create();
// Files are written to ./workspace by default
const { tools } = await createBashTool({
  sandbox,
  files: { "index.ts": "console.log('hello');" },
});

Persistent sandbox across serverless invocations

Use Sandbox.get to reconnect to an existing sandbox by ID:

import { Sandbox } from "@vercel/sandbox";

// First invocation: create sandbox and store the ID
const newSandbox = await Sandbox.create();
const sandboxId = newSandbox.sandboxId;
// Store sandboxId in database, session, or return to client

// Subsequent invocations: reconnect to existing sandbox
const existingSandbox = await Sandbox.get({ sandboxId });
const { tools } = await createBashTool({ sandbox: existingSandbox });
// All previous files and state are preserved

Use a custom just-bash instance

import { Bash } from "just-bash";

const sandbox = new Bash({ cwd: "/app" });
const { tools } = await createBashTool({
  sandbox,
  destination: "/app",
});

Intercept bash commands

const { tools } = await createBashTool({
  onBeforeBashCall: ({ command }) => {
    console.log("Running:", command);
    // Optionally modify the command
    if (command.includes("rm -rf")) {
      return { command: "echo 'Blocked dangerous command'" };
    }
  },
  onAfterBashCall: ({ command, result }) => {
    console.log(`Exit code: ${result.exitCode}`);
    // Optionally modify the result
    return { result: { ...result, stdout: result.stdout.trim() } };
  },
});

Custom sandbox implementation

import { createBashTool, Sandbox } from "bash-tool";

const customSandbox: Sandbox = {
  async executeCommand(command) {
    // Your implementation here
    return { stdout: "", stderr: "", exitCode: 0 };
  },
  async readFile(path) {
    // Your implementation here
    return "";
  },
  async writeFiles(files) {
    // Your implementation here - files is Array<{path, content}>
  },
};

const { tools } = await createBashTool({ sandbox: customSandbox });

Skills (Experimental)

Skills are modular capabilities that extend agent functionality. Each skill is a directory containing a SKILL.md file with instructions and optional scripts.

import {
  experimental_createSkillTool as createSkillTool,
  createBashTool,
} from "bash-tool";
import { ToolLoopAgent } from "ai";

// Discover skills and get files to upload
const { loadSkill, files, instructions } = await createSkillTool({
  skillsDirectory: "./skills",
});

// Create bash tool with skill files
const { tools } = await createBashTool({
  files,
  extraInstructions: instructions,
});

// Use both tools with an agent
const agent = new ToolLoopAgent({
  model,
  tools: { loadSkill, ...tools },
});

Skill Directory Structure

skills/
├── csv/
│   ├── SKILL.md      # Required: instructions with YAML frontmatter
│   ├── analyze.sh    # Optional: scripts the agent can run
│   └── filter.sh
└── text/
    ├── SKILL.md
    └── search.sh

SKILL.md Format

---
name: csv
description: Analyze and transform CSV files
---

# CSV Processing

Use `./skills/csv/analyze.sh <file>` to analyze a CSV file.

How It Works

• createSkillTool discovers skills and returns:

  • loadSkill - Tool for the agent to load a skill's instructions on demand
  • files - All skill files to pass to createBashTool
  • instructions - Extra instructions listing available skills

• The agent sees skill names in the loadSkill tool description

• When the agent needs a skill, it calls loadSkill("csv") to get detailed instructions

• The agent uses bash to run scripts from ./skills/csv/

AI Agent Instructions

For AI agents working with bash-tool, additional guidance is available in AGENTS.md:

cat node_modules/bash-tool/dist/AGENTS.md

License

MIT