ftruncate.xml

<?xml version="1.0" encoding="utf-8"?>
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<refentry xml:id="function.ftruncate" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>ftruncate</refname>
  <refpurpose>将文件截断到指定的长度</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>bool</type><methodname>ftruncate</methodname>
   <methodparam><type>resource</type><parameter>stream</parameter></methodparam>
   <methodparam><type>int</type><parameter>size</parameter></methodparam>
  </methodsynopsis>
  <para>
   接受文件指针 <parameter>stream</parameter> 作为参数，并将文件大小截取为
   <parameter>size</parameter>。
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>stream</parameter></term>
     <listitem>
      <para>
       文件指针。
      </para>
      <note>
       <para>
        <parameter>stream</parameter> 必须打开写入。
       </para>
      </note>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>size</parameter></term>
     <listitem>
      <para>
       截断的大小。
      </para>
      <note>
       <para>
        If <parameter>size</parameter> is larger than the file then the file
        is extended with null bytes.
       </para>
       <para>
        If <parameter>size</parameter> is smaller than the file then the file
        is truncated to that size.
       </para>
      </note>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   &return.success;
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>文件截取示例</title>
    <programlisting role="php">
<![CDATA[
<?php
$filename = 'lorem_ipsum.txt';

$handle = fopen($filename, 'r+');
ftruncate($handle, rand(1, filesize($filename)));
rewind($handle);
echo fread($handle, filesize($filename));
fclose($handle);
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  <note>
   <para>
    文件指针<emphasis>不会</emphasis>改变。
   </para>
  </note>
 </refsect1>
 
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>fopen</function></member>
    <member><function>fseek</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>
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