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# dio_seek

(PHP 4 >= 4.2.0, PHP 5 <= 5.0.4)

dio_seek -- Seeks to pos on fd from whence

## 说明

int dio_seek ( resource fd, int pos [, int whence] )

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

例子 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);
?>`

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