600 lines
47 KiB
HTML
600 lines
47 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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<head><meta http-equiv="x-ua-compatible" content="ie=edge">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<title>std::wprintf, std::fwprintf, std::swprintf</title>
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<link rel="stylesheet" href="ext.css" />
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<link rel="stylesheet" href="site_modules.css" />
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</head>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_io_c_fwprintf skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<div id="content"><a id="top"></a>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>wprintf, <span style="font-size:0.7em; line-height:130%">std::</span>fwprintf, <span style="font-size:0.7em; line-height:130%">std::</span>swprintf</h1>
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<div id="bodyContent">
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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 id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<table class="t-dcl-begin">
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<tbody>
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<tr class="t-dsc-header">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-cwchar.html"><cwchar></a></code></div>
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</td>
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<td></td>
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<td></td>
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</tr>
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<tr class="t-dcl">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> wprintf<span class="br0">(</span> <span class="kw4">const</span> <span class="kw4">wchar_t</span><span class="sy2">*</span> format, ... <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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</tr>
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<tr class="t-dcl">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> fwprintf<span class="br0">(</span> <a href="cpp-io-c.html"><span class="kw1874">std::<span class="me2">FILE</span></span></a><span class="sy2">*</span> stream, <span class="kw4">const</span> <span class="kw4">wchar_t</span><span class="sy2">*</span> format, ... <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(2)</td>
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<td class="t-dcl-nopad"></td>
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</tr>
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<tr class="t-dcl">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> swprintf<span class="br0">(</span> <span class="kw4">wchar_t</span><span class="sy2">*</span> buffer, <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> size, <span class="kw4">const</span> <span class="kw4">wchar_t</span><span class="sy2">*</span> format, ... <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(3)</td>
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<td class="t-dcl-nopad"></td>
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</tr>
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<tr class="t-dcl-sep">
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<td></td>
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<td></td>
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<td></td>
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</tr>
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</tbody>
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</table>
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<p>从给定位置加载数据，转换它们到宽字符串等价版本，并写入结果到各种池。</p>
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<div class="t-li1"><span class="t-li">1)</span> 写结果到 <span class="t-lc"><a href="cpp-io-c.html">stdout</a></span> 。</div>
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<div class="t-li1"><span class="t-li">2)</span> 写结果到文件流 <code>stream</code> 。</div>
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<div class="t-li1"><span class="t-li">3)</span> 写结果到宽字符串 <code>buffer</code> 。至多写入 <span class="t-c"><span class="mw-geshi cpp source-cpp">size<span class="sy2">-</span><span class="nu0">1</span></span></span> 个宽字符，后随空宽字符。</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>stream</td>
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<td>-</td>
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<td>要写入的输出文件流</td>
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</tr>
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<tr class="t-par">
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<td>buffer</td>
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<td>-</td>
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<td>指向要写入的宽字符串的指针</td>
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</tr>
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<tr class="t-par">
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<td>size</td>
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<td>-</td>
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<td>至多可写入 <code>size - 1</code> 个字符，再加上空终止符</td>
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</tr>
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<tr class="t-par">
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<td>format</td>
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<td>-</td>
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<td>指向指定转译方式的空终止宽字符串的指针。
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<p>格式字符串由普通宽字符（除了 <code><b>%</b></code> ）和转换指定构成，前者被复制到输出流而无更改。每个转换指定拥有下列格式：</p>
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<dl>
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<dd>
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<ul>
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<li>引入的 <code><b>%</b></code> 字符</li>
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</ul>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li><span class="t-mark">(可选)</span>一或多个修改转换行为的标签：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li><code><b>-</b></code> ：转换结果在域内左校正（默认为右校正）</li>
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<li><code><b>+</b></code> ：有符号转换的符号始终前置于转换结果（默认结果前置负号仅当它为负）</li>
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<li><i>空格</i>：若有符号转换的结果不以符号开始，或为空，则前置空格于结果。若存在 <code>+</code> 标签则忽略<i>空格</i>。</li>
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<li><code><b>#</b></code> ：进行<i>替用形式</i>的转换。准确的效果见下表，其他情况下行为未定义。</li>
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<li><code><b>0</b></code> ：对于整数和浮点数转换，使用前导零代替<i>空格</i>字符填充域。对于整数，若显式指定精度，则忽略此标签。对于其他转换，使用此标签导致未定义行为。若存在 <code>-</code> 标签则忽略 <code>0</code> 。</li>
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</ul>
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</dd>
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</dl>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li><span class="t-mark">(可选)</span>指定最小域宽的整数值或 <code>*</code> 。若有要求，则结果会以<i>空格</i>字符（默认情况）填充，在右校正时于左，左校正时于右。使用 <code>*</code> 的情况下，以一个额外的 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span></span></span> 类型参数指定宽度。若参数值为负数，则它导致指定 <code>-</code> 标签和正域宽。（注意：这是最小宽度：决不被截断值）。</li>
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</ul>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li><span class="t-mark">(可选)</span>后随整数或 <code><b>*</b></code> 或两者皆无的 <code><b>.</b></code> 指示转换的<i>精度</i>。在使用 <code>*</code> 的情况下，<i>精度</i>由额外的 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span></span></span> 类型参数指定。若此参数的值为负数，则它被忽略。若既不使用数字亦不使用 <code><b>*</b></code> ，则精度采用零。<i>精度</i>的准确效果见下表。</li>
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</ul>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li><span class="t-mark">(可选)</span>指定参数大小的<i>长度修饰符</i></li>
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</ul>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li>转换格式指定符</li>
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</ul>
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</dd>
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</dl>
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<p>下列格式指定符可用：</p>
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<table class="wikitable" style="text-align:center; font-size:85%; max-width:90em;">
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<tr>
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<th rowspan="1">转换<br />
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指定符</th>
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<th rowspan="1">解释</th>
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<th colspan="9">参数类型</th>
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</tr>
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<tr>
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<th colspan="2" style="text-align:right; font-weight:normal;">长度修饰符</th>
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<th><code>hh</code>
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<p><span class="t-mark-rev t-since-cxx11">(C++11)</span></p>
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</th>
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<th><code>h</code></th>
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<th style="font-weight:normal;">（无）</th>
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<th><code><b>l</b></code></th>
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<th><code><b>ll</b></code>
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<p><span class="t-mark-rev t-since-cxx11">(C++11)</span></p>
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</th>
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<th><code><b>j</b></code>
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<p><span class="t-mark-rev t-since-cxx11">(C++11)</span></p>
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</th>
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<th><code><b>z</b></code>
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<p><span class="t-mark-rev t-since-cxx11">(C++11)</span></p>
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</th>
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<th><code><b>t</b></code>
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<p><span class="t-mark-rev t-since-cxx11">(C++11)</span></p>
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</th>
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<th><code><b>L</b></code></th>
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</tr>
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<tr>
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<th><code>%</code></th>
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<td style="text-align:left;">写字面的 <code><b>%</b></code> 。完整转换指定必须是 <code><b>%%</b></code> 。</td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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</tr>
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<tr>
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<th><code>c</code></th>
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<td style="text-align:left;">
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<dl>
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<dd>写<b>单个字符</b>。</dd>
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</dl>
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<p>参数首先被转换成 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">wchar_t</span></span></span> ，如同通过调用 <span class="t-lc">btowc</span> 。 若使用 <b>l</b> 修饰符，则 <code>wint_t</code> 参数首先被转换成 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">wchar_t</span></span></span> 。</p>
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</td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td>
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<div class="t-vertical">
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<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span></span></span></div>
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</div>
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</td>
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<td>
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<div class="t-vertical">
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<div><span class="t-c"><span class="mw-geshi cpp source-cpp">wint_t</span></span></div>
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</div>
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</td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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</tr>
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<tr>
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<th><code>s</code></th>
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<td style="text-align:left;">
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<dl>
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<dd>写<b>字符串</b></dd>
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</dl>
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<p>参数必须为一个指针，指向包含以初始迁移状态开始的，多字节字符序列的字符数组首元素，数组会被转换成宽字符数组，如同通过以零初始化转换状态调用 <span class="t-lc">mbrtowc</span> 。 <i>精度</i>指定写入的最大宽字符数。若未指定<i>精度</i>，则写每个宽字符直到而不含首个空终止符。 若使用 <b>l</b> 指定符，则参数必须是指向 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">wchar_t</span></span></span> 数组首元素的指针。</p>
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</td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td>
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<div class="t-vertical">
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<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char</span><span class="sy2">*</span></span></span></div>
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</div>
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</td>
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<td>
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<div class="t-vertical">
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<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">wchar_t</span><span class="sy2">*</span></span></span></div>
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</div>
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</td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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</tr>
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<tr>
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<th><code>d</code><br />
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<code>i</code></th>
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<td style="text-align:left;">
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<dl>
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<dd>转换<b>有符号整数</b>为十进制表示 <i>[-]dddd</i> 。</dd>
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</dl>
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<p><i>精度</i>指定出现的最小数位数。默认精度是 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">1</span></span></span> 。<br />
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若被转换的值和精度都是 <span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> ，则转换结果无字符。</p>
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</td>
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<td rowspan="1">
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<div class="t-vertical">
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<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">signed</span> <span class="kw4">char</span></span></span></div>
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</div>
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</td>
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<td rowspan="1">
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<div class="t-vertical">
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<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">short</span></span></span></div>
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</div>
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</td>
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<td rowspan="1">
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<div class="t-vertical">
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<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span></span></span></div>
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</div>
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</td>
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<td rowspan="1">
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<div class="t-vertical">
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<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span></span></span></div>
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</div>
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</td>
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<td rowspan="1">
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<div class="t-vertical">
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<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> <span class="kw4">long</span></span></span></div>
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</div>
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</td>
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<td rowspan="1">
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<div class="t-vertical">
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<div><span class="t-c"><span class="mw-geshi cpp source-cpp">intmax_t</span></span></div>
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</div>
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</td>
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<td rowspan="1">
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<div class="t-vertical">
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<div>有符号 <span class="t-c"><span class="mw-geshi cpp source-cpp">size_t</span></span></div>
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</div>
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</td>
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<td rowspan="1">
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<div class="t-vertical">
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<div><span class="t-c"><span class="mw-geshi cpp source-cpp">ptrdiff_t</span></span></div>
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</div>
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</td>
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<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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</tr>
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<tr>
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<th><code>o</code></th>
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<td style="text-align:left;">
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<dl>
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<dd>转换<b>无符号整数</b>为八进制表示 <i>oooo</i> 。</dd>
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</dl>
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<p><i>精度</i>指定出现的最小数位数。默认精度是 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">1</span></span></span> 。 若被转换值和精度都是 <span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> ，则转换结果无字符。 在<i>替用实现</i>中精度按需增加，以写入一个前导零。 在此情况下若被转换值和精度都是 <span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> ，则写入单个 <span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> 。</p>
|
|
</td>
|
|
<td rowspan="3">
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">char</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td rowspan="3">
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">short</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td rowspan="3">
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">int</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td rowspan="3">
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">long</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td rowspan="3">
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">long</span> <span class="kw4">long</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td rowspan="3">
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp">uintmax_t</span></span></div>
|
|
</div>
|
|
</td>
|
|
<td rowspan="3">
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp">size_t</span></span></div>
|
|
</div>
|
|
</td>
|
|
<td rowspan="3">
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp">ptrdiff_t</span></span> 的无符号版本</div>
|
|
</div>
|
|
</td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
</tr>
|
|
<tr>
|
|
<th><code>x</code><br />
|
|
<code>X</code></th>
|
|
<td style="text-align:left;">
|
|
<dl>
|
|
<dd>转换<b>无符号整数</b>为十六进制表示 <i>hhhh</i> 。</dd>
|
|
</dl>
|
|
<p><code><b>x</b></code> 转换使用字母 <code>abcdef</code> 。<br />
|
|
<code><b>X</b></code> 转换使用 <code>ABCDEF</code> 。<br />
|
|
<i>精度</i>指定出现的最小数位数。默认精度是 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">1</span></span></span> 。 若被转换值和精度都是 <span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> ，则转换结果无字符。 在<i>替用实现中</i>若被转换值为非零则结果有 <code><b>0x</b></code> 或 <code><b>0X</b></code> 前缀。</p>
|
|
</td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
</tr>
|
|
<tr>
|
|
<th><code>u</code></th>
|
|
<td style="text-align:left;">
|
|
<dl>
|
|
<dd>转换<b>无符号整数</b>为十进制表示 <i>dddd</i> 。</dd>
|
|
</dl>
|
|
<p><i>精度</i>指定出现的最小数位数。 默认精度是 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">1</span></span></span> 。 若被转换值和精度都是 <span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> ，则转换结果无字符。</p>
|
|
</td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
</tr>
|
|
<tr>
|
|
<th><code>f</code><br />
|
|
<code>F</code></th>
|
|
<td style="text-align:left;">
|
|
<dl>
|
|
<dd>转换<b>浮点数</b>为 <i>[-]ddd.ddd</i> 样式的十进制记法。</dd>
|
|
</dl>
|
|
<p><i>精度</i>指定小数点字符后出现的准确数位数。 默认精度是 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">6</span></span></span> 。 在<i>替用实现</i>中即使没有小数点后数位也写小数点。 无穷大和非数的转换样式见注意。</p>
|
|
</td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td rowspan="4">
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">double</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td rowspan="4">
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">double</span></span></span> <span class="t-mark-rev t-since-cxx11">(C++11)</span></div>
|
|
</div>
|
|
</td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td rowspan="4">
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> <span class="kw4">double</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<th><code>e</code><br />
|
|
<code>E</code></th>
|
|
<td style="text-align:left;">
|
|
<dl>
|
|
<dd>转换<b>浮点数</b>为十进制指数记法。</dd>
|
|
</dl>
|
|
<p><code><b>e</b></code> 转换样式使用 <i>[-]d.ddd</i><code><b>e</b></code><i>±dd</i> 。<br />
|
|
<code><b>E</b></code> 转换样式使用 <i>[-]d.ddd</i><code><b>E</b></code><i>±dd</i> 。<br />
|
|
指数至少含二个数位，仅当所需时使用更多数位。 若值为 <span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> ，则指数亦为 <span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> 。 <i>精度</i>指定小数点字符后出现的最小数位数。 默认精度是 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">6</span></span></span> 。 在<i>替用实现</i>中即使没有小数点后数位也写小数点。 无穷大和非数的转换样式见注意。</p>
|
|
</td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
</tr>
|
|
<tr>
|
|
<th><code>a</code><br />
|
|
<code>A</code>
|
|
<p><span class="t-mark-rev t-since-cxx11">(C++11)</span></p>
|
|
</th>
|
|
<td style="text-align:left;">
|
|
<dl>
|
|
<dd>转换<b>浮点数</b>为十六进制记法。</dd>
|
|
</dl>
|
|
<p><code><b>a</b></code> 转换样式使用 <i>[-]</i><code><b>0x</b></code><i>h.hhh</i><code><b>p</b></code><i>±d</i> 。<br />
|
|
<code><b>A</b></code> 转换样式使用 <i>[-]</i><code><b>0X</b></code><i>h.hhh</i><code><b>P</b></code><i>±d</i> 。<br />
|
|
若参数是正规化的浮点值，则首个十六进制数位非 <code>0</code> 。 若值为 <span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> ，则指数亦为 <span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> 。 <i>精度</i>指定小数点字符后出现的最小数位数。 默认精度足以准确表示该值。 在<i>替用实现</i>中即使没有小数点后数位也写小数点。 无穷大和非数的转换样式见注意。</p>
|
|
</td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
</tr>
|
|
<tr>
|
|
<th><code>g</code><br />
|
|
<code>G</code></th>
|
|
<td style="text-align:left;">
|
|
<dl>
|
|
<dd>转换<b>浮点数</b>为十进制小数或十进制指数记法，依赖于值和<i>精度</i>。</dd>
|
|
</dl>
|
|
<p><code><b>g</b></code> 转换样式将进行带样式 <code><b>e</b></code> 或 <code><b>f</b></code> 的转换。<br />
|
|
<code><b>G</b></code> 转换样式将进行带样式 <code><b>E</b></code> 或 <code><b>F</b></code> 的转换。<br />
|
|
令 <code>P</code> 等于精度，若它非零，若精度未指定则为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">6</span></span></span> ，若精度为 <span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> 则等于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">1</span></span></span> 。然后，若带样式 <code>E</code> 的转换会有指数 <code>X</code> ，则：</p>
|
|
<ul>
|
|
<li>若 <i>P > X ≥ −4</i> ，则转换带 <code><b>f</b></code> 或 <code><b>F</b></code> 风格，及精度 <i>P − 1 − X</i> 。</li>
|
|
<li>否则，转换带 <code><b>e</b></code> 或 <code><b>E</b></code> 风格，及精度 <i>P − 1</i> 。</li>
|
|
</ul>
|
|
<p>除非要求<i>替用表示</i>，否则末尾零会被移除，且若不留下小数部分则小数点亦被移除。 无穷大和非数的转换样式见注意。</p>
|
|
</td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
</tr>
|
|
<tr>
|
|
<th><code>n</code></th>
|
|
<td style="text-align:left;">
|
|
<dl>
|
|
<dd>返回对函数的此调用迄今为止<b>写入的字符数</b>。</dd>
|
|
</dl>
|
|
<p>结果被<i>写入</i>到参数所指向的值。 该指定不可含有任何<i>标签</i>、<i>域宽</i>或<i>精度</i>。</p>
|
|
</td>
|
|
<td>
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">signed</span> <span class="kw4">char</span><span class="sy2">*</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">short</span><span class="sy2">*</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span><span class="sy2">*</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span><span class="sy2">*</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> <span class="kw4">long</span><span class="sy2">*</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp">intmax_t<span class="sy2">*</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>
|
|
<div class="t-vertical">
|
|
<div>有符号 <span class="t-c"><span class="mw-geshi cpp source-cpp">size_t<span class="sy2">*</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp">ptrdiff_t<span class="sy2">*</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
</tr>
|
|
<tr>
|
|
<th><code>p</code></th>
|
|
<td style="text-align:left;">写定义<b>指针</b>的实现定义字符序列。</td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span><span class="sy2">*</span></span></span></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
|
</tr>
|
|
</table>
|
|
<p>浮点转换函数转换无穷大到 <code>inf</code> 或 <code>infinity</code> 。使用哪个是实现定义的。</p>
|
|
<p>非数转换成 <code>nan</code> 或 <code>nan(<i>char_sequence</i>)</code> 。使用哪个是实现定义的。</p>
|
|
<p>转换 <code><b>F</b></code> 、 <code><b>E</b></code> 、 <code><b>G</b></code> 、 <code><b>A</b></code> 替代上面输出 <code>INF</code> 、 <code>INFINITY</code> 、 <code>NAN</code>。</p>
|
|
<p>尽管 <code>%c</code> 期待 <code>int</code> 参数，传递 <code>char</code> 是安全的，因为在调用变参数函数时发生整数提升。</p>
|
|
<p>定宽整数类型（ <span class="t-lc">int8_t</span> 等）的正确转换指定定义于头文件 <a href="cpp-types-integer.html"><cinttypes></a> （尽管 <span class="t-lc"><a href="cpp-types-integer.html">PRIdMAX</a></span> 、 <span class="t-lc"><a href="cpp-types-integer.html">PRIuMAX</a></span> 等就是 <code>%jd</code> 、 <code>%ju</code> 等的别名）。</p>
|
|
<p>内存写入转换指定符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>n</span></span> 是安全漏洞的常见目标，这里格式字符串依赖用户输入，而有边界检查的 <code>printf_s</code> 系列函数不支持此转换指定符。</p>
|
|
<p>在每个转换指定符的行动后有一个<a href="cpp-language-eval_order.html">序列点</a>；这允许于同一变量多次存入 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>n</span></span> 的结果，并在同一此调用中打印出先前以 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>n</span></span> 存储的值。</p>
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<p>若转换指定非法，则行为未定义。</p>
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<p><br /></p>
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</td>
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</tr>
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<tr class="t-par">
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<td>...</td>
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<td>-</td>
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<td>指定要打印的数据的参数。若任何参数在<a href="cpp-language-variadic_arguments.html#.E9.BB.98.E8.AE.A4.E8.BD.AC.E6.8D.A2">默认转换</a>后不拥有对应转换指定符所期待的类型，或若参数少于 <code>format</code> 所要求的数量，则行为未定义。若有多于 <code>format</code> 所要求的参数，则求值并忽略额外参数</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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<div class="t-li1"><span class="t-li">1,2)</span> 若成功则为写入的宽字符数，若出现错误则为负值。</div>
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<div class="t-li1"><span class="t-li">3)</span> 若成功则为写入的宽字符数（不计终止空宽字符），或若出现编码错误，或若生成的字符数等于或大于 <code>size</code> （包含 <code>size</code> 为零时）则为负值。</div>
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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>窄字符串提供 <span class="t-lc"><a href="cpp-io-c-fprintf.html">std::snprintf</a></span> ，它使得程序能够确定要求的输出缓冲区大小。不过宽字符串无等价版本，而且为确定缓冲区大小，程序需要调用 <code>std::swprintf</code> ，检查结果值，再重新分配更大的缓冲区，反复尝试直至成功。</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="t-example">
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<div class="t-example-live-link"></div>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <iostream></span>
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<span class="co2">#include <locale></span>
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<span class="co2">#include <clocale></span>
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<span class="co2">#include <cwchar></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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<span class="kw4">char</span> narrow_str<span class="br0">[</span><span class="br0">]</span> <span class="sy1">=</span> <span class="st0">"z<span class="es3">\u00df</span><span class="es3">\u6c34</span><span class="es4">\U0001f34c</span>"</span><span class="sy4">;</span>
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<span class="co1">// 或 "zß水🍌"</span>
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<span class="co1">// 或 "\x7a\xc3\x9f\xe6\xb0\xb4\xf0\x9f\x8d\x8c";</span>
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<span class="kw4">wchar_t</span> warr<span class="br0">[</span><span class="nu0">29</span><span class="br0">]</span><span class="sy4">;</span> <span class="co1">// 期待的字符串为 28 字符加 1 个空终止符</span>
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<a href="cpp-locale-setlocale.html"><span class="kw1987">std::<span class="me2">setlocale</span></span></a><span class="br0">(</span><a href="cpp-locale-LC_categories.html"><span class="kw1990">LC_ALL</span></a>, <span class="st0">"en_US.utf8"</span><span class="br0">)</span><span class="sy4">;</span>
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std<span class="sy4">::</span><span class="me2">swprintf</span><span class="br0">(</span>warr, sizeof warr<span class="sy2">/</span>sizeof <span class="sy2">*</span>warr,
|
|
L<span class="st0">"Converted from UTF-8: '%s'"</span>, narrow_str<span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1759">std::<span class="me2">wcout</span></span></a>.<span class="me1">imbue</span><span class="br0">(</span><a href="cpp-locale-locale.html"><span class="kw1891">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="st0">"en_US.utf8"</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1759">std::<span class="me2">wcout</span></span></a> <span class="sy1"><<</span> warr <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
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</div>
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|
<p>输出：</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="text source-text">
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|
<pre class="de1">Converted from UTF-8: 'zß水🍌'</pre></div>
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</div>
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</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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<tr class="t-dsc">
|
|
<td>
|
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<div class="t-dsc-member-div">
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|
<div><a href="cpp-io-c-fprintf.html"><span class="t-lines"><span>printf</span><span>fprintf</span><span>sprintf</span><span>snprintf</span></span></a></div>
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<div><span class="t-lines"><span></span><span></span><span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>打印有格式输出到 <span class="t-lc"><a href="cpp-io-c.html">stdout</a></span>、文件流或缓冲区<br />
|
|
<span class="t-mark">(函数)</span></td>
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</tr>
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<tr class="t-dsc">
|
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<td>
|
|
<div class="t-dsc-member-div">
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|
<div><a href="cpp-io-c-vfwprintf.html"><span class="t-lines"><span>vwprintf</span><span>vfwprintf</span><span>vswprintf</span></span></a></div>
|
|
</div>
|
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</td>
|
|
<td>使用可变实参列表打印<br />
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有格式宽字符输出到 <span class="t-lc"><a href="cpp-io-c.html">stdout</a></span>、文件流或缓冲区<br />
|
|
<span class="t-mark">(函数)</span></td>
|
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</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
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|
<div><a href="cpp-io-c-fputws.html"><span class="t-lines"><span>fputws</span></span></a></div>
|
|
</div>
|
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</td>
|
|
<td>写宽字符串到文件流<br />
|
|
<span class="t-mark">(函数)</span></td>
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</tr>
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</table>
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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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</html>
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