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---
name: Spawn a child process and communicate using IPC
---
Use [`Bun.spawn()`](/docs/api/spawn) 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.
{%callout%}
**Note** — This API is only compatible with other `bun` processes. Use `process.execPath` to get a path to the currently running `bun` executable.
{%/callout%}
```ts#parent.ts
const child = Bun.spawn(["bun", "child.ts"], {
ipc(message) {
/**
* The message received from the sub process
**/
},
});
```
---
The parent process can send messages to the subprocess using the `.send()` method on the returned `Subprocess` instance. A reference to the sending subprocess is also available as the second argument in the `ipc` handler.
```ts#parent.ts
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
```
---
Meanwhile the child process can send messages to its parent using with `process.send()` and receive messages with `process.on("message")`. This is the same API used for `child_process.fork()` in Node.js.
```ts#child.ts
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 using the JSC `serialize` API, which allows for the same set of [transferrable types](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Transferable_objects) supported by `postMessage` and `structuredClone`, including strings, typed arrays, streams, and objects.
```ts#child.ts
// send a string
process.send("Hello from child as string");
// send an object
process.send({ message: "Hello from child as object" });
```
---
See [Docs > API > Child processes](/docs/api/spawn) for complete documentation.
|
