129 lines
8.6 KiB
HTML
129 lines
8.6 KiB
HTML
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<title>std::feof</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_io_c_feof skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>feof</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-io.html">io</a>‎ | <a href="cpp-io-c.html">c</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-cstdio.html"><cstdio></a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> feof<span class="br0">(</span> <a href="cpp-io-c.html"><span class="kw1876">std::<span class="me2">FILE</span></span></a><span class="sy2">*</span> stream <span class="br0">)</span><span class="sy4">;</span></span></div>
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<p>检查是否已抵达给定文件流的结尾。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<table class="t-par-begin">
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<td>stream</td>
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<td>-</td>
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<td>要检查的文件流</td>
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</tr>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<p>若已抵达文件流尾则为非零值，否则为 <span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> 。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">注意</span></h3>
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<p>此函数只报告最近的 I/O 操作所报告的流状态，它不检验关联数据源。例如，若最近一次 I/O 是返回文件最后字节的 <span class="t-lc"><a href="cpp-io-c-fgetc.html">std::fgetc</a></span> ，则 <code>std::feof</code> 返回零。下个 <span class="t-lc"><a href="cpp-io-c-fgetc.html">std::fgetc</a></span> 失败并更改文件流为<i>文件尾</i>。只在这之后 <code>std::feof</code> 才返回非零。</p>
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<p>典型用法中，输入流在任何错误时停止处理；然后用 <code>feof</code> 和 <span class="t-lc"><a href="cpp-io-c-ferror.html">std::ferror</a></span> 区别不同的错误条件。</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <cstdio></span>
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<span class="co2">#include <cstdlib></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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FILE<span class="sy2">*</span> fp <span class="sy1">=</span> <a href="cpp-io-c-fopen.html"><span class="kw1813">std::<span class="me2">fopen</span></span></a><span class="br0">(</span><span class="st0">"test.txt"</span>, <span class="st0">"r"</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">if</span><span class="br0">(</span><span class="sy3">!</span>fp<span class="br0">)</span> <span class="br0">{</span>
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<a href="cpp-io-c-perror.html"><span class="kw1872">std::<span class="me2">perror</span></span></a><span class="br0">(</span><span class="st0">"File opening failed"</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">return</span> <a href="cpp-utility-program-EXIT_status.html"><span class="kw973">EXIT_FAILURE</span></a><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw4">int</span> c<span class="sy4">;</span> <span class="co1">// 注意：是 int 而非 char ，要求处理 EOF</span>
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<span class="kw1">while</span> <span class="br0">(</span><span class="br0">(</span>c <span class="sy1">=</span> <a href="cpp-io-c-fgetc.html"><span class="kw1821">std::<span class="me2">fgetc</span></span></a><span class="br0">(</span>fp<span class="br0">)</span><span class="br0">)</span> <span class="sy3">!</span><span class="sy1">=</span> <a href="cpp-io-c.html"><span class="kw1881">EOF</span></a><span class="br0">)</span> <span class="br0">{</span> <span class="co1">// 标准 C I/O 文件读取循环</span>
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<a href="cpp-io-c-putchar.html"><span class="kw1829">std::<span class="me2">putchar</span></span></a><span class="br0">(</span>c<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw1">if</span> <span class="br0">(</span><a href="cpp-io-c-ferror.html"><span class="kw1871">std::<span class="me2">ferror</span></span></a><span class="br0">(</span>fp<span class="br0">)</span><span class="br0">)</span>
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<a href="cpp-io-c-puts.html"><span class="kw1830">std::<span class="me2">puts</span></span></a><span class="br0">(</span><span class="st0">"I/O error when reading"</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">else</span> <span class="kw1">if</span> <span class="br0">(</span>std<span class="sy4">::</span><span class="me2">feof</span><span class="br0">(</span>fp<span class="br0">)</span><span class="br0">)</span>
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<a href="cpp-io-c-puts.html"><span class="kw1830">std::<span class="me2">puts</span></span></a><span class="br0">(</span><span class="st0">"End of file reached successfully"</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-c-fclose.html"><span class="kw1816">std::<span class="me2">fclose</span></span></a><span class="br0">(</span>fp<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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<div class="t-dsc-member-div">
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<div><a href="cpp-io-basic_ios-eof.html"><span class="t-lines"><span>eof</span></span></a></div>
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</div>
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</td>
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<td>检查是否到达了文件末尾<br />
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<span class="t-mark">(<code>std::basic_ios<CharT,Traits></code> 的公开成员函数)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-io-c-clearerr.html"><span class="t-lines"><span>clearerr</span></span></a></div>
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</div>
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</td>
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<td>清除错误<br />
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<span class="t-mark">(函数)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-io-c-perror.html"><span class="t-lines"><span>perror</span></span></a></div>
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</div>
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</td>
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<td>显示对应当前错误的字符串于 <span class="t-lc"><a href="cpp-io-c.html">stderr</a></span><br />
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<span class="t-mark">(函数)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-io-c-ferror.html"><span class="t-lines"><span>ferror</span></span></a></div>
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</td>
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<td>检查文件错误<br />
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<span class="t-mark">(函数)</span></td>
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</table>
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</div>
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<div class="visualClear"></div>
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