(PHP 4 >= 4.2.0, PHP 5 < 5.1.0)
dio_truncate — Truncates file descriptor fd to offset bytes
$fd, int $offset): bool
dio_truncate() truncates a file to at most
offset bytes in size.
If the file previously was larger than this size, the extra data is lost. If the file previously was shorter, it is unspecified whether the file is left unchanged or is extended. In the latter case the extended part reads as zero bytes.
成功時(shí)返回 true， 或者在失敗時(shí)返回 false。
注意: 此函數未在 Windows 平臺下實(shí)現。