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153 lines
6.7 KiB
HTML
153 lines
6.7 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<meta http-equiv="content-type" content="text/html; charset=UTF-8">
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<title>在文件指针中定位</title>
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</head>
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<body class="docs"><div id="layout">
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<div id="layout-content"><div id="function.fseek" class="refentry">
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<div class="refnamediv">
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<h1 class="refname">fseek</h1>
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<p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">fseek</span> — <span class="dc-title">在文件指针中定位</span></p>
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</div>
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<div class="refsect1 description" id="refsect1-function.fseek-description">
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<h3 class="title">说明</h3>
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<div class="methodsynopsis dc-description">
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<span class="methodname"><strong>fseek</strong></span>
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( <span class="methodparam"><span class="type">resource</span> <code class="parameter">$handle</code></span>
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, <span class="methodparam"><span class="type">int</span> <code class="parameter">$offset</code></span>
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[, <span class="methodparam"><span class="type">int</span> <code class="parameter">$whence</code><span class="initializer"> = SEEK_SET</span></span>
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] ) : <span class="type">int</span></div>
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<p class="para rdfs-comment">
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在与
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<code class="parameter">handle</code>
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关联的文件中设定文件指针位置。
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新位置从文件头开始以字节数度量，是以
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<code class="parameter">whence</code>
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指定的位置加上
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<code class="parameter">offset</code>。
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</p>
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<p class="para">
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In general, it is allowed to seek past the end-of-file; if data is then
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written, reads in any unwritten region between the end-of-file and the
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sought position will yield bytes with value 0. However, certain streams
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may not support this behavior, especially when they have an underlying
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fixed size storage.
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</p>
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</div>
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<div class="refsect1 parameters" id="refsect1-function.fseek-parameters">
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<h3 class="title">参数</h3>
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<p class="para">
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<dl>
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<dt>
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<code class="parameter">handle</code></dt>
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<dd>
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<p class="para">文件系统指针，是典型地由
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<span class="function"><a href="fopen.html" class="function">fopen()</a></span> 创建的 <span class="type"><a href="language.types.resource.html" class="type resource">resource</a></span>(资源)。</p>
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</dd>
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<dt>
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<code class="parameter">offset</code></dt>
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<dd>
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<p class="para">
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偏移量。
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</p>
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<p class="para">
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要移动到文件尾之前的位置，需要给
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<code class="parameter">offset</code> 传递一个负值，并设置 <code class="parameter">whence</code>
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为 <strong><code>SEEK_END</code></strong>。
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</p>
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</dd>
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<dt>
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<code class="parameter">whence</code></dt>
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<dd>
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<p class="para">
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<code class="parameter">whence</code> values are:
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<ul class="simplelist">
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<li class="member"><strong><code>SEEK_SET</code></strong> - 设定位置等于 <code class="parameter">offset</code> 字节。</li>
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<li class="member"><strong><code>SEEK_CUR</code></strong> - 设定位置为当前位置加上 <code class="parameter">offset</code>。</li>
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<li class="member"><strong><code>SEEK_END</code></strong> - 设定位置为文件尾加上
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<code class="parameter">offset</code>。</li>
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</ul>
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</p>
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</dd>
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</dl>
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</p>
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</div>
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<div class="refsect1 returnvalues" id="refsect1-function.fseek-returnvalues">
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<h3 class="title">返回值</h3>
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<p class="para">
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成功则返回 0；否则返回 -1。注意移动到 EOF 之后的位置不算错误。
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</p>
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</div>
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<div class="refsect1 examples" id="refsect1-function.fseek-examples">
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<h3 class="title">范例</h3>
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<p class="para">
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<div class="example" id="example-2806">
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<p><strong>Example #1 <span class="function"><strong>fseek()</strong></span> 例子</strong></p>
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<div class="example-contents">
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<div class="phpcode"><pre><span style="color: #000000">
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<span style="color: #0000BB"><?php<br /><br />$fp </span><span style="color: #007700">= </span><span style="color: #0000BB">fopen</span><span style="color: #007700">(</span><span style="color: #DD0000">'somefile.txt'</span><span style="color: #007700">, </span><span style="color: #DD0000">'r'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// read some data<br /></span><span style="color: #0000BB">$data </span><span style="color: #007700">= </span><span style="color: #0000BB">fgets</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">, </span><span style="color: #0000BB">4096</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// move back to the beginning of the file<br />// same as rewind($fp);<br /></span><span style="color: #0000BB">fseek</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">?></span>
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</span>
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</pre></div>
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</div>
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</div>
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</p>
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</div>
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<div class="refsect1 notes" id="refsect1-function.fseek-notes">
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<h3 class="title">注释</h3>
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<blockquote class="note"><p><strong class="note">Note</strong>:
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<p class="para">
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如果使用附加模试（<em>a</em> 或 <em>a+</em>），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 <span class="function"><strong>fseek()</strong></span> 的结果尚未定义。
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</p>
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</p></blockquote>
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<blockquote class="note"><p><strong class="note">Note</strong>:
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<p class="para">
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Not all streams support seeking. For those that do not support seeking,
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forward seeking from the current position is accomplished by reading
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and discarding data; other forms of seeking will fail.
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</p>
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</p></blockquote>
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</div>
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<div class="refsect1 seealso" id="refsect1-function.fseek-seealso">
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<h3 class="title">参见</h3>
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<p class="para">
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<ul class="simplelist">
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<li class="member"><span class="function"><a href="ftell.html" class="function" rel="rdfs-seeAlso">ftell()</a> - 返回文件指针读/写的位置</span></li>
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<li class="member"><span class="function"><a href="rewind.html" class="function" rel="rdfs-seeAlso">rewind()</a> - 倒回文件指针的位置</span></li>
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</ul>
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</p>
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</div>
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</div></div></div></body></html> |