> ## Documentation Index
> Fetch the complete documentation index at: https://bun-1dd33a4e-farm-ad2450b3-transpiler-cache-version-namespa.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Spawn a child process and communicate using IPC

Use [`Bun.spawn()`](/runtime/child-process) to spawn a child process. When spawning a second `bun` process, you can open a direct inter-process communication (IPC) channel between the two processes.

<Note>
  This API is only compatible with other `bun` processes. Use `process.execPath` to get a path to the currently running
  `bun` executable.
</Note>

```ts parent.ts icon="https://mintcdn.com/bun-1dd33a4e-farm-ad2450b3-transpiler-cache-version-namespa/pVrMBuZvntvIe2NO/icons/typescript.svg?fit=max&auto=format&n=pVrMBuZvntvIe2NO&q=85&s=81fcaf3ac2cead5d758f3588a492f46a" theme={"theme":{"light":"github-light","dark":"dracula"}}
const child = Bun.spawn(["bun", "child.ts"], {
  ipc(message) {
    /**
     * The message received from the sub process
     **/
  },
});
```

***

The parent process sends messages to the subprocess with the `.send()` method on the returned `Subprocess` instance. The `ipc` handler also receives the subprocess as its second argument.

```ts parent.ts icon="https://mintcdn.com/bun-1dd33a4e-farm-ad2450b3-transpiler-cache-version-namespa/pVrMBuZvntvIe2NO/icons/typescript.svg?fit=max&auto=format&n=pVrMBuZvntvIe2NO&q=85&s=81fcaf3ac2cead5d758f3588a492f46a" theme={"theme":{"light":"github-light","dark":"dracula"}}
const childProc = Bun.spawn(["bun", "child.ts"], {
  ipc(message, childProc) {
    /**
     * The message received from the sub process
     **/
    childProc.send("Respond to child");
  },
});

childProc.send("I am your father"); // The parent can send messages to the child as well
```

***

The child process sends messages to its parent with `process.send()` and receives messages with `process.on("message")`. This is the same API used for `child_process.fork()` in Node.js.

```ts child.ts icon="https://mintcdn.com/bun-1dd33a4e-farm-ad2450b3-transpiler-cache-version-namespa/pVrMBuZvntvIe2NO/icons/typescript.svg?fit=max&auto=format&n=pVrMBuZvntvIe2NO&q=85&s=81fcaf3ac2cead5d758f3588a492f46a" theme={"theme":{"light":"github-light","dark":"dracula"}}
process.send("Hello from child as string");
process.send({ message: "Hello from child as object" });

process.on("message", message => {
  // print message from parent
  console.log(message);
});
```

***

All messages are serialized with the JSC `serialize` API, which supports the same set of [transferrable types](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Transferable_objects) as `postMessage` and `structuredClone`, including strings, typed arrays, streams, and objects.

```ts child.ts icon="https://mintcdn.com/bun-1dd33a4e-farm-ad2450b3-transpiler-cache-version-namespa/pVrMBuZvntvIe2NO/icons/typescript.svg?fit=max&auto=format&n=pVrMBuZvntvIe2NO&q=85&s=81fcaf3ac2cead5d758f3588a492f46a" theme={"theme":{"light":"github-light","dark":"dracula"}}
// send a string
process.send("Hello from child as string");

// send an object
process.send({ message: "Hello from child as object" });
```

***

See [Child processes](/runtime/child-process).