# dio_seek

(PHP 4 >= 4.2.0, PHP 5 < 5.1.0)

dio_seek — Seeks to pos on fd from whence

### 说明

dio_seek ( resource `$fd` , int `$pos` [, int `$whence` = SEEK_SET ] ) : int

The function dio_seek() is used to change the file position of the given file descriptor.

### 参数

`fd`

  The file descriptor returned by dio_open().

`pos`

  The new position.

`whence`

  Specifies how the position `pos` should be interpreted:

  - `SEEK_SET` (default) - specifies that `pos` is specified from the beginning of the file.

  - `SEEK_CUR` - Specifies that `pos` is a count of characters from the current file position. This count may be positive or negative.

  - `SEEK_END` - Specifies that `pos` is a count of characters from the end of the file. A negative count specifies a position within the current extent of the file; a positive count specifies a position past the current end. If you set the position past the current end, and actually write data, you will extend the file with zeros up to that position.

### 返回值

### 范例

Example #1 Positioning in a file

    <?php

    $fd = dio_open('/dev/ttyS0', O_RDWR);

    dio_seek($fd, 10, SEEK_SET);
    // position is now at 10 characters from the start of the file

    dio_seek($fd, -2, SEEK_CUR);
    // position is now at 8 characters from the start of the file

    dio_seek($fd, -5, SEEK_END);
    // position is now at 5 characters from the end of the file

    dio_seek($fd, 10, SEEK_END);
    // position is now at 10 characters past the end of the file.
    // The 10 characters between the end of the file and the current
    // position are filled with zeros.

    dio_close($fd);
    ?>