<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >dio_seek</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REL="HOME" TITLE="PHP 手册" HREF="index.html"><LINK REL="UP" TITLE="Direct IO Functions" HREF="ref.dio.html"><LINK REL="PREVIOUS" TITLE="dio_read" HREF="function.dio-read.html"><LINK REL="NEXT" TITLE="dio_stat" HREF="function.dio-stat.html"><META HTTP-EQUIV="Content-type" CONTENT="text/html; charset=UTF-8"></HEAD ><BODY CLASS="refentry" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >PHP 手册</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="function.dio-read.html" ACCESSKEY="P" >上一页</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="function.dio-stat.html" ACCESSKEY="N" >下一页</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="function.dio-seek" ></A >dio_seek</H1 ><DIV CLASS="refnamediv" ><A NAME="AEN36315" ></A ><P > (PHP 4 >= 4.2.0, PHP 5 <= 5.0.4)</P >dio_seek -- Seeks to pos on fd from whence</DIV ><DIV CLASS="refsect1" ><A NAME="AEN36318" ></A ><H2 >说明</H2 >int <B CLASS="methodname" >dio_seek</B > ( resource fd, int pos [, int whence] )<BR ></BR ><P > The function <B CLASS="function" >dio_seek()</B > is used to change the file position of the given file descriptor. </P ></DIV ><DIV CLASS="refsect1" ><A NAME="AEN36334" ></A ><H2 >参数</H2 ><P > <P ></P ><DIV CLASS="variablelist" ><DL ><DT ><CODE CLASS="parameter" >fd</CODE ></DT ><DD ><P > The file descriptor returned by <A HREF="function.dio-open.html" ><B CLASS="function" >dio_open()</B ></A >. </P ></DD ><DT ><CODE CLASS="parameter" >pos</CODE ></DT ><DD ><P > The new position. </P ></DD ><DT ><CODE CLASS="parameter" >whence</CODE ></DT ><DD ><P > Specifies how the position <CODE CLASS="parameter" >pos</CODE > should be interpreted: <P ></P ><UL ><LI ><P > <TT CLASS="constant" ><B >SEEK_SET</B ></TT > (default) - specifies that <CODE CLASS="parameter" >pos</CODE > is specified from the beginning of the file. </P ></LI ><LI ><P > <TT CLASS="constant" ><B >SEEK_CUR</B ></TT > - Specifies that <CODE CLASS="parameter" >pos</CODE > is a count of characters from the current file position. This count may be positive or negative. </P ></LI ><LI ><P > <TT CLASS="constant" ><B >SEEK_END</B ></TT > - Specifies that <CODE CLASS="parameter" >pos</CODE > 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. </P ></LI ></UL > </P ></DD ></DL ></DIV > </P ></DIV ><DIV CLASS="refsect1" ><A NAME="AEN36368" ></A ><H2 >返回值</H2 ><P > </P ></DIV ><DIV CLASS="refsect1" ><A NAME="AEN36371" ></A ><H2 >范例</H2 ><P > <TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" CLASS="EXAMPLE" ><TR ><TD ><DIV CLASS="example" ><A NAME="AEN36374" ></A ><P ><B >例 1. Positioning in a file</B ></P ><TABLE BORDER="0" BGCOLOR="#E0E0E0" CELLPADDING="5" ><TR ><TD ><code><font color="#000000"> <font color="#0000BB"><?php<br /><br />$fd </font><font color="#007700">= </font><font color="#0000BB">dio_open</font><font color="#007700">(</font><font color="#DD0000">'/dev/ttyS0'</font><font color="#007700">, </font><font color="#0000BB">O_RDWR</font><font color="#007700">);<br /><br /></font><font color="#0000BB">dio_seek</font><font color="#007700">(</font><font color="#0000BB">$fd</font><font color="#007700">, </font><font color="#0000BB">10</font><font color="#007700">, </font><font color="#0000BB">SEEK_SET</font><font color="#007700">);<br /></font><font color="#FF8000">// position is now at 10 characters from the start of the file<br /><br /></font><font color="#0000BB">dio_seek</font><font color="#007700">(</font><font color="#0000BB">$fd</font><font color="#007700">, -</font><font color="#0000BB">2</font><font color="#007700">, </font><font color="#0000BB">SEEK_CUR</font><font color="#007700">);<br /></font><font color="#FF8000">// position is now at 8 characters from the start of the file<br /><br /></font><font color="#0000BB">dio_seek</font><font color="#007700">(</font><font color="#0000BB">$fd</font><font color="#007700">, -</font><font color="#0000BB">5</font><font color="#007700">, </font><font color="#0000BB">SEEK_END</font><font color="#007700">);<br /></font><font color="#FF8000">// position is now at 5 characters from the end of the file<br /><br /></font><font color="#0000BB">dio_seek</font><font color="#007700">(</font><font color="#0000BB">$fd</font><font color="#007700">, </font><font color="#0000BB">10</font><font color="#007700">, </font><font color="#0000BB">SEEK_END</font><font color="#007700">);<br /></font><font color="#FF8000">// position is now at 10 characters past the end of the file. <br />// The 10 characters between the end of the file and the current<br />// position are filled with zeros.<br /><br /></font><font color="#0000BB">dio_close</font><font color="#007700">(</font><font color="#0000BB">$fd</font><font color="#007700">);<br /></font><font color="#0000BB">?></font> </font> </code></TD ></TR ></TABLE ></DIV ></TD ></TR ></TABLE > </P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="function.dio-read.html" ACCESSKEY="P" >上一页</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >起始页</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="function.dio-stat.html" ACCESSKEY="N" >下一页</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >dio_read</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="ref.dio.html" ACCESSKEY="U" >上一级</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >dio_stat</TD ></TR ></TABLE ></DIV ></BODY ></HTML >