207 lines
15 KiB
HTML
207 lines
15 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>wcsncat, wcsncat_s</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_string_wide_wcsncat 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">wcsncat, wcsncat_s</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="c.html">c</a>‎ | <a href="c-string.html">string</a>‎ | <a href="c-string-wide.html">wide</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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<td>
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<div>定义于头文件 <code><wchar.h></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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</tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<td></td>
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<td rowspan="142">(1)</td>
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<td></td>
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<tr class="t-dcl t-since-c95 t-until-c99">
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<td>
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<div><span class="mw-geshi c source-c"><span class="kw4">wchar_t</span> <span class="sy2">*</span>wcsncat<span class="br0">(</span> <span class="kw4">wchar_t</span> <span class="sy2">*</span>dest, <span class="kw4">const</span> <span class="kw4">wchar_t</span> <span class="sy2">*</span>src, <a href="c-types-size_t.html"><span class="kw100">size_t</span></a> count <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-c95">(C95 起)</span><br />
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<span class="t-mark-rev t-until-c99">(C99 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-c99">
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<div><span class="mw-geshi c source-c"><span class="kw4">wchar_t</span> <span class="sy2">*</span>wcsncat<span class="br0">(</span> <span class="kw4">wchar_t</span> <span class="sy2">*</span><span class="kw4">restrict</span> dest,<br />
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<span class="kw4">const</span> <span class="kw4">wchar_t</span> <span class="sy2">*</span><span class="kw4">restrict</span> src, <a href="c-types-size_t.html"><span class="kw100">size_t</span></a> count <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-c99">(C99 起)</span></td>
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</tbody>
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<tbody>
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<tr class="t-dcl t-since-c11">
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<div><span class="mw-geshi c source-c">errno_t wcsncat_s<span class="br0">(</span> <span class="kw4">wchar_t</span> <span class="sy2">*</span><span class="kw4">restrict</span> dest, rsize_t destsz,<br />
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<span class="kw4">const</span> <span class="kw4">wchar_t</span> <span class="sy2">*</span><span class="kw4">restrict</span> src, rsize_t count <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><span class="t-mark-rev t-since-c11">(C11 起)</span></td>
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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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<div class="t-li1"><span class="t-li">1)</span> 后附来自 <code>src</code> 所指向的宽字符串的至多 <code>count</code> 个宽字符，到 <code>dest</code> 所指向的字符串末尾，若找到空字符则停止。宽字符 <span class="t-c"><span class="mw-geshi c source-c">src<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span></span></span> 替换位于 <code>dest</code> 末尾的空终止符。始终后附终止空字符到末尾（故函数可写入的最大宽字符数是 <span class="t-c"><span class="mw-geshi c source-c">count<span class="sy2">+</span><span class="nu0">1</span></span></span> ）。</div>
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<div class="t-li1"><span class="t-li"></span> 若目标数组没有对于 <code>dest</code> 和 <code>src</code> 的内容加上终止空宽字符足够的空间，则行为未定义。</div>
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<div class="t-li1"><span class="t-li"></span> 若字符串重叠则行为未定义。</div>
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<div class="t-li1"><span class="t-li">2)</span> 同 <span class="t-v">(1)</span> ，除了此函数可以可用未指定值破坏目标数组的剩余部分（从最后写入宽字符到 <code>destsz</code> ），以及在运行时检测下列错误，并调用当前安装的<a href="c-error-set_constraint_handler_s.html">制约处理</a>函数：
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<dl>
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<dd>
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<ul>
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<li><code>src</code> 或 <code>dest</code> 为空指针</li>
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<li><code>destsz</code> 或 <code>count</code> 为零或大于 <span class="t-c"><span class="mw-geshi c source-c">RSIZE_MAX<span class="sy2">/</span><span class="kw4">sizeof</span><span class="br0">(</span><span class="kw4">wchar_t</span><span class="br0">)</span></span></span></li>
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<li><code>dest</code> 的首 <code>destsz</code> 个宽字符中无空宽字符</li>
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<li>会出现截断： <code>count</code> 与 <code>src</code> 长度的较小者，会超出 <code>dest</code> 的空终止符和 <code>destsz</code> 之间的可用空间。</li>
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<li>源与目标字符串之间会出现重叠</li>
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</ul>
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</dd>
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<dd></dd>
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<dd>同所有边界检查函数， <code>wcsncat_s</code> 仅若实现定义了 <span class="t-c"><span class="mw-geshi c source-c">__STDC_LIB_EXT1__</span></span> ，且用户在包含 <code>wchar.h</code> 前定义 <span class="t-c"><span class="mw-geshi c source-c">__STDC_WANT_LIB_EXT1__</span></span> 为整数常量 <span class="t-c"><span class="mw-geshi c source-c"><span class="nu0">1</span></span></span> 才保证可用。</dd>
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</dl>
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</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>dest</td>
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<td>-</td>
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<td>指向要后附到的空终止宽字符串的指针</td>
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</tr>
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<tr class="t-par">
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<td>src</td>
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<td>-</td>
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<td>指向作为复制来源的宽字符数组的指针</td>
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</tr>
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<tr class="t-par">
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<td>count</td>
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<td>-</td>
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<td>要复制的最大宽字符数</td>
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</tr>
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<tr class="t-par">
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<td>destsz</td>
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<td>-</td>
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<td>目标缓冲区的大小</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)</span> 返回 <code>dest</code> 的副本。</div>
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<div class="t-li1"><span class="t-li">2)</span> 成功时返回零。错误时返回非零。错误时，亦写入 <span class="t-c"><span class="mw-geshi c source-c">L<span class="st0">'<span class="es5">\0</span>'</span></span></span> 到 <span class="t-c"><span class="mw-geshi c source-c">dest<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span></span></span> （除非 <code>dest</code> 为空指针，或 <code>destsz</code> 为零或大于 <span class="t-c"><span class="mw-geshi c source-c">RSIZE_MAX<span class="sy2">/</span><span class="kw4">sizeof</span><span class="br0">(</span><span class="kw4">wchar_t</span><span class="br0">)</span></span></span> ）。</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>尽管截断以适应目标缓冲区是安全风险，从而是 <code>wcsncat_s</code> 的运行时制约违规，还是可以通过指定 <code>count</code> 等于目标数组大小减一获取截断行为：这将一如往常地复制首 <code>count</code> 个宽字符并后附空终止符： <span class="t-c"><span class="mw-geshi c source-c">wcsncat_s<span class="br0">(</span>dst, <span class="kw4">sizeof</span> dst<span class="sy2">/</span><span class="kw4">sizeof</span> <span class="sy2">*</span>dst, src, <span class="br0">(</span><span class="kw4">sizeof</span> dst<span class="sy2">/</span><span class="kw4">sizeof</span> <span class="sy2">*</span>dst<span class="br0">)</span><span class="sy2">-</span>wcsnlen_s<span class="br0">(</span>dst, <span class="kw4">sizeof</span> dst<span class="sy2">/</span><span class="kw4">sizeof</span> <span class="sy2">*</span>dst<span class="br0">)</span><span class="sy2">-</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span></span></span> 。</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="c source-c">
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<pre class="de1"><span class="co2">#include <wchar.h> </span>
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<span class="co2">#include <stdio.h></span>
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<span class="co2">#include <locale.h></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw4">wchar_t</span> str<span class="br0">[</span><span class="nu0">50</span><span class="br0">]</span> <span class="sy1">=</span> L<span class="st0">"Земля, прощай."</span><span class="sy4">;</span>
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wcsncat<span class="br0">(</span>str, L<span class="st0">" "</span>, <span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span>
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wcsncat<span class="br0">(</span>str, L<span class="st0">"В добрый путь."</span>, <span class="nu0">8</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 只后附首 8 个宽字符</span>
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<a href="c-locale-setlocale.html"><span class="kw900">setlocale</span></a><span class="br0">(</span><a href="c-locale-LC_categories.html"><span class="kw903">LC_ALL</span></a>, <span class="st0">"en_US.utf8"</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"%ls"</span>, str<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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<p>可能的输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">Земля, прощай. В добрый</pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">引用</span></h3>
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<div class="t-ref-std-11">
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<ul>
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<li>C11 标准（ISO/IEC 9899:2011）：</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>7.29.4.3.2 The wcsncat function (p: 432-433)</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>K.3.9.2.2.2 The wcsncat_s function (p: 643-644)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c99">
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<ul>
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<li>C99 标准（ISO/IEC 9899:1999）：</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>7.24.4.3.2 The wcsncat function (p: 378-379)</li>
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</ul>
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</dd>
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</dl>
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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">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="c-string-wide-wcscat.html"><span class="t-lines"><span>wcscat</span><span>wcscat_s</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-c95">(C95)</span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div>
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</div>
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</td>
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<td>将一个宽字符串的副本后附于另一个<br />
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<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>
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<div class="t-dsc-member-div">
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<div><a href="c-string-byte-strncat.html"><span class="t-lines"><span>strncat</span><span>strncat_s</span></span></a></div>
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<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div>
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</div>
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</td>
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<td>连接两个字符串的一定数量字符<br />
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<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>
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<div class="t-dsc-member-div">
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<div><a href="c-string-wide-wcscpy.html"><span class="t-lines"><span>wcscpy</span><span>wcscpy_s</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-c95">(C95)</span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div>
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</div>
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</td>
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<td>将一个宽字符串复制给另一个<br />
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<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>
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<div class="visualClear"></div>
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