WriteAllowPartialSuccessAsync

:::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. :::

Write data, waiting if necessary

public function writeAllowPartialSuccessAsync(
  string $bytes,
  ?int $timeout_ns = NULL,
): Awaitable<int>;

A wrapper around write() that will wait if write() would throw an OS\BlockingIOException

It is possible for the write to partially succeed - check the return value and call again if needed.

Parameters

• string $bytes
• ?int $timeout_ns = NULL

Returns

• the - number of bytes written, which may be less than the length of input string.