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fseek.xml
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fseek.xml
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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<!-- EN-Revision: 0c9c2dd669fe9395eaa73d487fbd160f9057429a Maintainer: dallas Status: ready -->
<!-- CREDITS: mowangjuanzi -->
<refentry xml:id="function.fseek" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>fseek</refname>
<refpurpose>在文件指针中定位</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>int</type><methodname>fseek</methodname>
<methodparam><type>resource</type><parameter>stream</parameter></methodparam>
<methodparam><type>int</type><parameter>offset</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>whence</parameter><initializer><constant>SEEK_SET</constant></initializer></methodparam>
</methodsynopsis>
<para>
在与 <parameter>stream</parameter> 关联的文件中设定文件指针位置。新位置从文件头开始以字节数度量,是以
<parameter>whence</parameter> 指定的位置加上 <parameter>offset</parameter>。
</para>
<para>
In general, it is allowed to seek past the end-of-file; if data is then
written, reads in any unwritten region between the end-of-file and the
sought position will yield bytes with value 0. However, certain streams
may not support this behavior, especially when they have an underlying
fixed size storage.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>stream</parameter></term>
<listitem>
&fs.file.pointer;
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>offset</parameter></term>
<listitem>
<para>
偏移量。
</para>
<para>
要移动到文件尾之前的位置,需要给 <parameter>offset</parameter> 传递一个负值,并设置
<parameter>whence</parameter> 为 <constant>SEEK_END</constant>。
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>whence</parameter></term>
<listitem>
<para>
<parameter>whence</parameter> 值是:
<simplelist>
<member><constant>SEEK_SET</constant> - 设定位置等于 <parameter>offset</parameter> 字节。</member>
<member><constant>SEEK_CUR</constant> - 设定位置为当前位置加上 <parameter>offset</parameter>。</member>
<member><constant>SEEK_END</constant> - 设定位置为文件尾加上 <parameter>offset</parameter>。</member>
</simplelist>
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
成功则返回 0;否则返回 -1。
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title><function>fseek</function> 例子</title>
<programlisting role="php">
<![CDATA[
<?php
$fp = fopen('somefile.txt', 'r');
// read some data
$data = fgets($fp, 4096);
// move back to the beginning of the file
// same as rewind($fp);
fseek($fp, 0);
?>
]]>
</programlisting>
</example>
</para>
</refsect1>
<refsect1 role="notes">
&reftitle.notes;
<note>
<para>
如果使用附加模试(<literal>a</literal> 或
<literal>a+</literal>),任何写入文件数据都会被附加上去,而文件的位置将会被忽略,调用
<function>fseek</function> 的结果尚未定义。
</para>
</note>
<note>
<para>
Not all streams support seeking. For those that do not support seeking,
forward seeking from the current position is accomplished by reading
and discarding data; other forms of seeking will fail.
</para>
</note>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>ftell</function></member>
<member><function>rewind</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
<!-- Keep this comment at the end of the file
Local variables:
mode: sgml
sgml-omittag:t
sgml-shorttag:t
sgml-minimize-attributes:nil
sgml-always-quote-attributes:t
sgml-indent-step:1
sgml-indent-data:t
indent-tabs-mode:nil
sgml-parent-document:nil
sgml-default-dtd-file:"~/.phpdoc/manual.ced"
sgml-exposed-tags:nil
sgml-local-catalogs:nil
sgml-local-ecat-files:nil
End:
vim600: syn=xml fen fdm=syntax fdl=2 si
vim: et tw=78 syn=sgml
vi: ts=1 sw=1
-->