Bun Shell Has a Built-in Shell Scripting Language — Here's How to Use It

Bun introduced something most JavaScript developers never expected — a built-in shell scripting language that runs cross-platform.

What is Bun Shell?

Bun Shell (Bun.$) is a cross-platform shell built into the Bun runtime. It lets you run shell commands using tagged template literals with full JavaScript interop.

Quick Start

import { $ } from "bun";

// Run any shell command
await $`echo Hello from Bun Shell!`;

// Capture output
const result = await $`ls -la`.text();
console.log(result);

// Use JavaScript variables seamlessly
const dir = "./src";
await $`find ${dir} -name "*.ts" | wc -l`;

Why Bun Shell Matters

1. Cross-Platform by Default

// This works on macOS, Linux, AND Windows
await $`echo $HOME`; // Uses Bun's built-in shell, not system shell
await $`cat file.txt | grep pattern`;

2. JavaScript Interop

const files = ["a.txt", "b.txt", "c.txt"];
for (const file of files) {
  await $`cat ${file} >> combined.txt`;
}

// Pipe to JavaScript
const output = await $`curl -s https://api.example.com/data`.json();
console.log(output.results);

3. Error Handling

try {
  await $`exit 1`;
} catch (err) {
  console.log(err.exitCode); // 1
  console.log(err.stderr.toString());
}

// Or use .nothrow() to suppress errors
const result = await $`maybe-missing-command`.nothrow();
if (result.exitCode !== 0) {
  console.log("Command failed, but we handled it");
}

4. Piping and Redirects

// Pipe between commands
await $`cat data.json | jq .items[] | sort | uniq`;

// Redirect to file
await $`echo "Hello" > output.txt`;
await $`echo "World" >> output.txt`;

// Pipe to Response (for HTTP servers)
const server = Bun.serve({
  fetch(req) {
    return new Response($`cat large-file.txt`.stdout);
  },
});

Real-World Use Cases

Build Scripts

// build.ts
import { $ } from "bun";

await $`rm -rf dist`;
await $`bun build ./src/index.ts --outdir ./dist`;
await $`cp -r public/* dist/`;
console.log("Build complete!");

Database Backup Script

import { $ } from "bun";

const date = new Date().toISOString().split("T")[0];
const dbUrl = process.env.DATABASE_URL;

await $`pg_dump ${dbUrl} | gzip > backups/db-${date}.sql.gz`;
await $`echo Backup created: backups/db-${date}.sql.gz`;

Dev Environment Setup

import { $ } from "bun";

// Check dependencies
await $`docker compose up -d`;
await $`bun install`;
await $`bun run db:migrate`;
await $`echo Dev environment ready!`;

Bun Shell vs Alternatives

Feature	Bun Shell	zx (Google)	execa	child_process
Cross-platform	Yes	Partial	Yes	No
Template literals	Yes	Yes	No	No
Built-in (no install)	Yes	No	No	Yes
JavaScript interop	Native	Good	Good	Manual
Performance	Fast	Moderate	Good	Varies

Performance

Bun Shell is significantly faster than spawning system shells because it uses Bun's built-in shell implementation. No fork/exec overhead for basic operations.

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