bun-types/docs/guides/process/spawn-stderr.md

Type definitions and documentation for Bun, an incredibly fast JavaScript runtime

---
name: Read stderr from a child process
---

When using [`Bun.spawn()`](https://bun.sh/docs/api/spawn), the child process inherits the `stderr` of the spawning process. If instead you'd prefer to read and handle `stderr`, set the `stderr` option to `"pipe"`.

```ts
const proc = Bun.spawn(["echo", "hello"], {
  stderr: "pipe",
});
proc.stderr; // => ReadableStream
```

---

To read `stderr` until the child process exits, use the [`Bun.readableStreamToText()`](https://bun.sh/docs/api/utils#bun-readablestreamto) convenience function.

```ts
const proc = Bun.spawn(["echo", "hello"], {
  stderr: "pipe",
});

const errors: string = await Bun.readableStreamToText(proc.stderr);
if (errors) {
  // handle errors
}
```

---

See [Docs > API > Child processes](https://bun.sh/docs/api/spawn) for complete documentation.