Files are closed by calling close(2). close(2) cancels any outstanding asynchronous I/O request that can be. close(2) waits for an operation that cannot be cancelled (see "aiocancel(3AIO)"). When close(2) returns, there is no asynchronous I/O pending for the file descriptor. Only asynchronous I/O requests queued to the specified file descriptor are cancelled when a file is closed. Any I/O pending requests for other file descriptors are not cancelled.