Stderr

:::info[Note] This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information. :::

Get a file descriptor for request STDERR

namespace HH\Lib\OS;

function stderr(): FileDescriptor;

Fails with EBADF if a request-specific file descriptor is not available, for example, when running in HTTP server mode.

Returns

• FileDescriptor