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);
?>