161 lines
9.8 KiB
HTML
161 lines
9.8 KiB
HTML
<!DOCTYPE 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::basic_ifstream<CharT,Traits>::open</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_io_basic_ifstream_open skin-cppreference2 action-view cpp-page-template cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::basic_ifstream<CharT,Traits>::</span>open</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-basic_ifstream.html">basic ifstream</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<div class="t-page-template" style="">
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<p></p>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span> open<span class="br0">(</span> <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy2">*</span>filename,<br />
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ios_base<span class="sy4">::</span><span class="me2">openmode</span> mode <span class="sy1">=</span> ios_base<span class="sy4">::</span><span class="me2">in</span> <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(1)</td>
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<td class="t-dcl-nopad"></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span> open<span class="br0">(</span> <span class="kw4">const</span> std<span class="sy4">::</span><span class="me2">filesystem</span><span class="sy4">::</span><span class="me2">path</span><span class="sy4">::</span><span class="me2">value_type</span> <span class="sy2">*</span>filename,<br />
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ios_base<span class="sy4">::</span><span class="me2">openmode</span> mode <span class="sy1">=</span> ios_base<span class="sy4">::</span><span class="me2">in</span> <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(2)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span> open<span class="br0">(</span> <span class="kw4">const</span> <a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> <span class="sy3">&</span>filename, <br />
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ios_base<span class="sy4">::</span><span class="me2">openmode</span> mode <span class="sy1">=</span> ios_base<span class="sy4">::</span><span class="me2">in</span> <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(3)</td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span> open<span class="br0">(</span> <span class="kw4">const</span> <a href="cpp-filesystem-path.html"><span class="kw2199">std::<span class="me2">filesystem</span><span class="sy4">::</span><span class="me2">path</span></span></a> <span class="sy3">&</span>filename, <br />
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ios_base<span class="sy4">::</span><span class="me2">openmode</span> mode <span class="sy1">=</span> ios_base<span class="sy4">::</span><span class="me2">in</span> <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(4)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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<td></td>
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<td></td>
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<p>将名为 <code>filename</code> 的文件打开并与文件流关联。</p>
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<p>失败时调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">setstate<span class="br0">(</span>failbit<span class="br0">)</span></span></span> 。</p>
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<table class="t-rev-begin">
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<td>成功时调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">clear<span class="br0">(</span><span class="br0">)</span></span></span> 。</td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<div class="t-li1"><span class="t-li">1-2)</span> 等效地调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">rdbuf<span class="br0">(</span><span class="br0">)</span><span class="sy2">-</span><span class="sy1">></span>open<span class="br0">(</span>filename, mode <span class="sy3">|</span> ios_base<span class="sy4">::</span><span class="me2">in</span><span class="br0">)</span></span></span>. （该调用效果上的细节见 <span class="t-lc"><a href="cpp-io-basic_filebuf-open.html">std::basic_filebuf::open</a></span> ）。<span class="t-rev-inl t-since-cxx17"><span>仅若 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">filesystem</span><span class="sy4">::</span><span class="me2">path</span><span class="sy4">::</span><span class="me2">value_type</span></span></span> 非 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char</span></span></span> 才提供重载 <span class="t-v">(2)</span> 。</span> <span><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></span></span></div>
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<div class="t-li1"><span class="t-li">3-4)</span> 等效地调用 <span class="t-v">(1-2)</span> ，如同以 <span class="t-c"><span class="mw-geshi cpp source-cpp">open<span class="br0">(</span>filename.<span class="me1">c_str</span><span class="br0">(</span><span class="br0">)</span>, mode<span class="br0">)</span></span></span> 。</div>
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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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<tr class="t-par">
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<td>filename</td>
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<td>-</td>
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<td>要打开的文件名</td>
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</tr>
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<tr class="t-par">
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<td>mode</td>
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<td>-</td>
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<td>指定打开模式。它是位掩码类型，定义下列常量：
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<table class="t-dsc-begin">
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<td>常量</td>
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<td>解释</td>
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<td><a href="cpp-io-ios_base-openmode.html"><tt>app</tt></a></td>
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<td>每次写入前寻位到流结尾</td>
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</tr>
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<tr class="t-dsc">
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<td><a href="cpp-io-ios_base-openmode.html"><tt>binary</tt></a></td>
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<td>以<a href="cpp-io-c-FILE.html#.E4.BA.8C.E8.BF.9B.E5.88.B6.E4.B8.8E.E6.96.87.E6.9C.AC.E6.A8.A1.E5.BC.8F">二进制模式</a>打开</td>
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</tr>
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<tr class="t-dsc">
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<td><a href="cpp-io-ios_base-openmode.html"><tt>in</tt></a></td>
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<td>为读打开</td>
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<tr class="t-dsc">
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<td><a href="cpp-io-ios_base-openmode.html"><tt>out</tt></a></td>
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<td>为写打开</td>
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</tr>
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<tr class="t-dsc">
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<td><a href="cpp-io-ios_base-openmode.html"><tt>trunc</tt></a></td>
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<td>在打开时舍弃流的内容</td>
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</tr>
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<tr class="t-dsc">
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<td><a href="cpp-io-ios_base-openmode.html"><tt>ate</tt></a></td>
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<td>打开后立即寻位到流结尾</td>
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</tr>
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</table>
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</td>
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</tr>
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</table>
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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>（无）</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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<table class="metadata plainlinks ambox mbox-small-left ambox-notice" style="">
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<td class="mbox-empty-cell"></td>
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<td class="mbox-text" style="">本节未完成<br />
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原因：暂无示例</td>
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</tr>
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</table>
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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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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-io-basic_ifstream-is_open.html"><span class="t-lines"><span>is_open</span></span></a></div>
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</div>
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</td>
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<td>检查流是否有关联文件<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-io-basic_ifstream-close.html"><span class="t-lines"><span>close</span></span></a></div>
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</div>
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</td>
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<td>关闭关联文件<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-io-basic_filebuf-open.html"><span class="t-lines"><span>open</span></span></a></div>
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</div>
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</td>
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<td>打开文件并配置它为关联字符序列<br />
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<span class="t-mark">(<code>std::basic_filebuf<CharT,Traits></code> 的公开成员函数)</span></td>
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</tr>
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</div>
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<div class="visualClear"></div>
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</div>
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</div>
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</div>
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</body>
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