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web/cppreference-zh/chmhelp/cpp-io-c-fscanf.html
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<!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::scanf, std::fscanf, std::sscanf</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_fscanf 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>scanf, <span style="font-size:0.7em; line-height:130%">std::</span>fscanf, <span style="font-size:0.7em; line-height:130%">std::</span>sscanf</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-cstdio.html"><cstdio></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> scanf<span class="br0">(</span> <span class="kw4">const</span> <span class="kw4">char</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> fscanf<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">char</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> sscanf<span class="br0">(</span> <span class="kw4">const</span> <span class="kw4">char</span><span class="sy2">*</span> buffer, <span class="kw4">const</span> <span class="kw4">char</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>从各种源读取数据，按照 <code>format</code> 转译并存储结果于给定位置。</p>
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<div class="t-li1"><span class="t-li">1)</span> 从 <span class="t-lc"><a href="cpp-io-c.html">stdin</a></span> 读数据</div>
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<div class="t-li1"><span class="t-li">2)</span> 从文件流 <code>stream</code> 读数据</div>
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<div class="t-li1"><span class="t-li">3)</span> 从空终止字符串 <code>buffer</code> 读数据</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>读取来源的文件流</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>指向读取数据来源的空终止字符串</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>指向指定如何读取输入的空终止字符串的指针。
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<p>格式字符串由下列内容组成</p>
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<ul>
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||||
<li>非空白多字节字符，除了 <code><b>%</b></code> ：每个格式字符串中的这种字符处理来自输入流的准确同一字符，或若它与流的下个字符比较不相等则导致函数失败。</li>
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<li>空白符：任何格式字符串中的单个空白符处理所有来自输入的可用连续空白符（如同通过于循环中调用 <a href="cpp-string-byte-isspace.html"><tt>isspace</tt></a> 确定）。注意格式字符串中 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"<span class="es1">\n</span>"</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">" "</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"<span class="es1">\t</span><span class="es1">\t</span>"</span></span></span> 或其他空白无区别。</li>
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<li>转换说明：每个转换说明拥有下列格式：</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>引入用 <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>赋值抑制字符 <code><b>*</b></code> 。若存在此选项，则此函数不将结果赋值给任何接收用参数。</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<i>最大域宽</i>的整数数字（大于零），即函数进行在当前转换说明所指定的转换时，允许处理的最大字符数。注意若不提供宽度，则 %s 和 %[ 可能导致缓冲区溢出。</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>指定接收参数大小的<i>长度修饰符</i>，即实际目标类型。这影响转换准确性和溢出规则。默认目标类型对每个转换类型不同（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>转换格式说明符</li>
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</ul>
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</dd>
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</dl>
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<p>下列格式说明符可用：</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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说明符</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;">
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<div style="display:inline-block; vertical-align:middle; text-align:center"><b>长度修饰符 →</b></div>
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</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;">匹配字面 <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>
|
||||
<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>
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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>匹配一个<b>字符</b>或<b>字符</b>的序列</dd>
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||||
</dl>
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||||
<p>若使用了宽度说明符，则匹配准确的<i>宽度</i>个字符（该参数必须是指向有充足空间的数组的指针）。不同于 %s 和 %[ ，它不会在数组后附加空字符。</p>
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||||
</td>
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||||
<td rowspan="3" style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
||||
<td rowspan="3" style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
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||||
<td rowspan="3">
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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>
|
||||
</div>
|
||||
</td>
|
||||
<td rowspan="3">
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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>
|
||||
</div>
|
||||
</td>
|
||||
<td rowspan="3" style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
||||
<td rowspan="3" style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
||||
<td rowspan="3" style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
||||
<td rowspan="3" style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
||||
<td rowspan="3" style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
||||
</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>匹配非空白字符的序列（一个<b>字符串</b>）</dd>
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||||
</dl>
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||||
<p>若使用宽度说明符，则至多匹配<i>宽度</i>个字符，或匹配到首个提前出现的空白符前。总是在匹配的字符后存储一个空字符（故参数数组必须有至少<i>宽度 +1</i> 个字符的空间）。</p>
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||||
</td>
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||||
</tr>
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||||
<tr>
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||||
<th><code>[</code><span class="t-spar">集合</span><code>]</code></th>
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||||
<td style="text-align:left;">
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||||
<dl>
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||||
<dd>匹配一个来自 <span class="t-spar">集合</span> 的字符的非空字符序列。</dd>
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||||
</dl>
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||||
<p>若集合的首字符是 <code>^</code> ，则匹配所有不在集合中的字符。若集合以 <code>]</code> 或 <code>^]</code> 开始，则 <code>]</code> 字符亦被包含入集合。在扫描集合的非最初位置的字符 <code>-</code> 是否可以指示范围，如 <code>[0-9]</code> ，是实现定义的。若使用宽度说明符，则最多匹配到<i>宽度</i>。总是在匹配的字符后存储一个空字符（故参数数组必须有至少<i>宽度 +1</i> 个字符的空间）。</p>
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||||
</td>
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||||
</tr>
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||||
<tr>
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||||
<th><code>d</code></th>
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||||
<td style="text-align:left;">
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||||
<dl>
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||||
<dd>匹配一个<b>十进制整数</b>。</dd>
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||||
</dl>
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||||
<p>该数的格式同 <a href="cpp-string-byte-strtol.html"><tt>strtol()</tt></a> 以值 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">10</span></span></span> 为 <code>base</code> 时所期望者</p>
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||||
</td>
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||||
<td rowspan="6">
|
||||
<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> 或 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">char</span><span class="sy2">*</span></span></span></div>
|
||||
</div>
|
||||
</td>
|
||||
<td rowspan="6">
|
||||
<div class="t-vertical">
|
||||
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">signed</span> <span class="kw4">short</span><span class="sy2">*</span></span></span> 或 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">short</span><span class="sy2">*</span></span></span></div>
|
||||
</div>
|
||||
</td>
|
||||
<td rowspan="6">
|
||||
<div class="t-vertical">
|
||||
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">signed</span> <span class="kw4">int</span><span class="sy2">*</span></span></span> 或 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">int</span><span class="sy2">*</span></span></span></div>
|
||||
</div>
|
||||
</td>
|
||||
<td rowspan="6">
|
||||
<div class="t-vertical">
|
||||
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">signed</span> <span class="kw4">long</span><span class="sy2">*</span></span></span> 或 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">long</span><span class="sy2">*</span></span></span></div>
|
||||
</div>
|
||||
</td>
|
||||
<td rowspan="6">
|
||||
<div class="t-vertical">
|
||||
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">signed</span> <span class="kw4">long</span> <span class="kw4">long</span><span class="sy2">*</span></span></span> 或 <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 class="sy2">*</span></span></span></div>
|
||||
</div>
|
||||
</td>
|
||||
<td rowspan="6">
|
||||
<div class="t-vertical">
|
||||
<div><span class="t-c"><span class="mw-geshi cpp source-cpp">intmax_t<span class="sy2">*</span></span></span> 或 <span class="t-c"><span class="mw-geshi cpp source-cpp">uintmax_t<span class="sy2">*</span></span></span></div>
|
||||
</div>
|
||||
</td>
|
||||
<td rowspan="6">
|
||||
<div class="t-vertical">
|
||||
<div><span class="t-c"><span class="mw-geshi cpp source-cpp">size_t<span class="sy2">*</span></span></span></div>
|
||||
</div>
|
||||
</td>
|
||||
<td rowspan="6">
|
||||
<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 rowspan="6" style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"><small>N/A</small></td>
|
||||
</tr>
|
||||
<tr>
|
||||
<th><code>i</code></th>
|
||||
<td style="text-align:left;">
|
||||
<dl>
|
||||
<dd>匹配一个<b>整数</b>。</dd>
|
||||
</dl>
|
||||
<p>该数的格式同 <a href="cpp-string-byte-strtol.html"><tt>strtol()</tt></a> 以值 <span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> 为 <code>base</code> 时所期望者（基底以首个分析的字符确定）</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<th><code>u</code></th>
|
||||
<td style="text-align:left;">
|
||||
<dl>
|
||||
<dd>匹配一个无符号<b>十进制整数</b>。</dd>
|
||||
</dl>
|
||||
<p>该数的格式同 <a href="cpp-string-byte-strtoul.html"><tt>strtoul()</tt></a> 以值 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">10</span></span></span> 为 <code>base</code> 参数时所期望者。</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<th><code>o</code></th>
|
||||
<td style="text-align:left;">
|
||||
<dl>
|
||||
<dd>匹配一个无符号<b>八进制数</b>。</dd>
|
||||
</dl>
|
||||
<p>该数的格式同 <a href="cpp-string-byte-strtoul.html"><tt>strtoul()</tt></a> 以值 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">8</span></span></span> 为 <code>base</code> 参数时所期望者。</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<th><code>x</code>, <code>X</code></th>
|
||||
<td style="text-align:left;">
|
||||
<dl>
|
||||
<dd>匹配一个无符号<b>十六进制整数</b>。</dd>
|
||||
</dl>
|
||||
<p>该数的格式同 <a href="cpp-string-byte-strtoul.html"><tt>strtoul()</tt></a> 以值 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">16</span></span></span> 为 <code>base</code> 参数时所期望者。</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<th><code>n</code></th>
|
||||
<td style="text-align:left;">
|
||||
<dl>
|
||||
<dd>返回<b>迄今读取的字符数</b>。</dd>
|
||||
</dl>
|
||||
<p>不消耗输出。不增加赋值计数。若此说明符拥有赋值抑制运算符，则行为未定义。</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<th><code>a</code>, <code>A</code><span class="t-mark-rev t-since-cxx11">(C++11)</span><br />
|
||||
<code>e</code>, <code>E</code><br />
|
||||
<code>f</code>, <code>F</code><br />
|
||||
<code>g</code>, <code>G</code></th>
|
||||
<td style="text-align:left;">
|
||||
<dl>
|
||||
<dd>匹配一个<b>浮点数</b>。</dd>
|
||||
</dl>
|
||||
<p>该数的格式同 <a href="cpp-string-byte-strtof.html"><tt>strtof()</tt></a> 所期望者。</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>
|
||||
<div class="t-vertical">
|
||||
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">float</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">double</span><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>
|
||||
<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>
|
||||
<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 class="sy2">*</span></span></span></div>
|
||||
</div>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<th><code>p</code></th>
|
||||
<td style="text-align:left;">
|
||||
<dl>
|
||||
<dd>匹配定义一个<b>指针</b>的实现定义的字符序列。</dd>
|
||||
</dl>
|
||||
<p><code>printf</code> 系列函数应该用 <code><b>%p</b></code> 格式说明符产生同样的序列。</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>
|
||||
<div class="t-vertical">
|
||||
<div><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span><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>
|
||||
<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>对于每个异于 <code>n</code> 的转换说明符，不超过任何指定域宽，且要么是转换说明符所准确期待，要么是其所期待的前缀的最长输入字符序列，即是从流中消耗的内容。此消耗序列后的首个字符若存在，则保持未读取。若被消耗序列长度为零，或被消耗序列不能转换成上面所指定的项目，则发生匹配失败，除非遇到文件尾、编码错误，或阻止从流输入的读取错误，此情况下此为输入失败。</p>
|
||||
<p>所有异于 <code>[</code> 、 <code>c</code> 和 <code>n</code> 的转换说明符，在尝试分析输入前消耗并舍弃所有前导空白字符（如同以调用 <a href="cpp-string-byte-isspace.html"><tt>isspace</tt></a> 来确定）。这些被消耗的字符不计入指定的最大域宽。</p>
|
||||
<p>转换说明符 <code>lc</code> 、 <code>ls</code> 和 <code>l[</code> 进行多字节到宽字符转换，如同如同在转换首字符前，通过用初始化到零的 <a href="cpp-string-multibyte-mbstate_t.html"><tt>mbstate_t</tt></a> 对象调用 <a href="cpp-string-multibyte-mbrtowc.html"><tt>mbrtowc()</tt></a> 。</p>
|
||||
<p>转换说明符 <code>s</code> 与 <code>[</code> 始终在匹配字符之后存储一个空字符。目标数组的大小必须至少比指定域宽大一。</p>
|
||||
<p><a href="cpp-types-integer.html">定宽整数类型</a>（ <code>int8_t</code> 等）的正确的转换说明定义于头文件 <a href="cpp-types-integer.html"><cinttypes></a> （虽然 <a href="cpp-types-integer.html"><tt>SCNdMAX</tt></a> 、 <a href="cpp-types-integer.html"><tt>SCNuMAX</tt></a> 等就是 <code>%jd</code> 、 <code>%ju</code> 等的别名）。</p>
|
||||
<p>在每个转换说明符后有一个<a href="cpp-language-eval_order.html">序列点</a>；这允许存储多个域到同一“池”变量中。</p>
|
||||
<p>在分析以无数字指数为结尾的不完整浮点值，如以转换说明符 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span>f</span></span> 分析 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"100er"</span></span></span> 时，消耗序列 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"100e"</span></span></span> （可能为合法浮点数的最长前缀），并导致匹配错误（被消耗序列不能转换成浮点数），而留下 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"r"</span></span></span> 。某些既存实现不遵守此规则并回滚，通过消耗 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"100"</span></span></span> 而留下 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"er"</span></span></span> ，例如 <a rel="nofollow" class="external text" href="https://sourceware.org/bugzilla/show_bug.cgi?id=1765">glibc 漏洞 1765</a> 。</p>
|
||||
<p><br /></p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr class="t-par">
|
||||
<td>...</td>
|
||||
<td>-</td>
|
||||
<td>接收的参数</td>
|
||||
</tr>
|
||||
</table>
|
||||
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
|
||||
<p>成功赋值的参数数（在首个参数赋值前发生匹配失败的情况下可为零），或若在赋值首个接收的参数前输入失败则为 <span class="t-lc"><a href="cpp-io-c.html">EOF</a></span> 。</p>
|
||||
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
|
||||
<p>因为大多数转换指定符首先消耗所有连续空白符，如下代码</p>
|
||||
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
||||
<div class="cpp source-cpp">
|
||||
<pre class="de1">std<span class="sy4">::</span><span class="me2">scanf</span><span class="br0">(</span><span class="st0">"%d"</span>, <span class="sy3">&</span>a<span class="br0">)</span><span class="sy4">;</span>
|
||||
std<span class="sy4">::</span><span class="me2">scanf</span><span class="br0">(</span><span class="st0">"%d"</span>, <span class="sy3">&</span>b<span class="br0">)</span><span class="sy4">;</span></pre></div>
|
||||
</div>
|
||||
<p>会读取输入于不同行（第二个 %d 会消耗第一个剩下的换行符）或同一行中为空格或制表符所分隔的（第二个 %d 会消耗空格或制表符）二个整数。</p>
|
||||
不消耗前导空白符的转换指定符，如 %c ，可通过在格式化字符串中用空白符使得它这么做：
|
||||
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
||||
<div class="cpp source-cpp">
|
||||
<pre class="de1">std<span class="sy4">::</span><span class="me2">scanf</span><span class="br0">(</span><span class="st0">"%d"</span>, <span class="sy3">&</span>a<span class="br0">)</span><span class="sy4">;</span>
|
||||
std<span class="sy4">::</span><span class="me2">scanf</span><span class="br0">(</span><span class="st0">" %c"</span>, <span class="sy3">&</span>c<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 忽略 %d 后的换行符，然后读一个 char</span></pre></div>
|
||||
</div>
|
||||
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
|
||||
<div class="t-example">
|
||||
<div class="t-example-live-link"></div>
|
||||
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
||||
<div class="cpp source-cpp">
|
||||
<pre class="de1"><span class="co2">#include <iostream></span>
|
||||
<span class="co2">#include <clocale></span>
|
||||
<span class="co2">#include <cstdio></span>
|
||||
|
||||
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
|
||||
<span class="br0">{</span>
|
||||
<span class="kw4">int</span> i, j<span class="sy4">;</span>
|
||||
<span class="kw4">float</span> x, y<span class="sy4">;</span>
|
||||
<span class="kw4">char</span> str1<span class="br0">[</span><span class="nu0">10</span><span class="br0">]</span>, str2<span class="br0">[</span><span class="nu0">4</span><span class="br0">]</span><span class="sy4">;</span>
|
||||
<span class="kw4">wchar_t</span> warr<span class="br0">[</span><span class="nu0">2</span><span class="br0">]</span><span class="sy4">;</span>
|
||||
<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>
|
||||
|
||||
<span class="kw4">char</span> input<span class="br0">[</span><span class="br0">]</span> <span class="sy1">=</span> u8<span class="st0">"25 54.32E-1 Thompson 56789 0123 56ß水"</span><span class="sy4">;</span>
|
||||
<span class="co1">// 按如下分析：</span>
|
||||
<span class="co1">// %d ：整数 </span>
|
||||
<span class="co1">// %f ：浮点值</span>
|
||||
<span class="co1">// %9s ：至多 9 个非空白字符的字符串</span>
|
||||
<span class="co1">// %2d ：二位整数（数字 5 与 6 ）</span>
|
||||
<span class="co1">// %f ：浮点值（数字 7 、 8 、 9 ）</span>
|
||||
<span class="co1">// %*d 不存储于任何位置的整数</span>
|
||||
<span class="co1">// ' ' ：所有连续空白符</span>
|
||||
<span class="co1">// %3[0-9] ：至多 3 位数字的字符串（数字 5 与 6 ）</span>
|
||||
<span class="co1">// %2lc ：二个宽字符，用多字节到宽转换</span>
|
||||
<span class="kw4">int</span> ret <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">sscanf</span><span class="br0">(</span>input, <span class="st0">"%d%f%9s%2d%f%*d %3[0-9]%2lc"</span>,
|
||||
<span class="sy3">&</span>i, <span class="sy3">&</span>x, str1, <span class="sy3">&</span>j, <span class="sy3">&</span>y, str2, warr<span class="br0">)</span><span class="sy4">;</span>
|
||||
|
||||
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Converted "</span> <span class="sy1"><<</span> ret <span class="sy1"><<</span> <span class="st0">" fields:<span class="es1">\n</span>"</span>
|
||||
<span class="sy1"><<</span> <span class="st0">"i = "</span> <span class="sy1"><<</span> i <span class="sy1"><<</span> <span class="st0">"<span class="es1">\n</span>x = "</span> <span class="sy1"><<</span> x <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
|
||||
<span class="sy1"><<</span> <span class="st0">"str1 = "</span> <span class="sy1"><<</span> str1 <span class="sy1"><<</span> <span class="st0">"<span class="es1">\n</span>j = "</span> <span class="sy1"><<</span> j <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
|
||||
<span class="sy1"><<</span> <span class="st0">"y = "</span> <span class="sy1"><<</span> y <span class="sy1"><<</span> <span class="st0">"<span class="es1">\n</span>str2 = "</span> <span class="sy1"><<</span> str2 <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
|
||||
<span class="sy1"><<</span> <a href="cpp-io-manip-hex.html"><span class="kw1782">std::<span class="me2">hex</span></span></a> <span class="sy1"><<</span> <span class="st0">"warr[0] = U+"</span> <span class="sy1"><<</span> warr<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span>
|
||||
<span class="sy1"><<</span> <span class="st0">" warr[1] = U+"</span> <span class="sy1"><<</span> warr<span class="br0">[</span><span class="nu0">1</span><span class="br0">]</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
||||
<span class="br0">}</span></pre></div>
|
||||
</div>
|
||||
<p>输出：</p>
|
||||
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
||||
<div class="text source-text">
|
||||
<pre class="de1">Converted 7 fields:
|
||||
i = 25
|
||||
x = 5.432
|
||||
str1 = Thompson
|
||||
j = 56
|
||||
y = 789
|
||||
str2 = 56
|
||||
warr[0] = U+df warr[1] = U+6c34</pre></div>
|
||||
</div>
|
||||
</div>
|
||||
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
|
||||
<table class="t-dsc-begin">
|
||||
<tr class="t-dsc">
|
||||
<td>
|
||||
<div class="t-dsc-member-div">
|
||||
<div><a href="cpp-io-c-vfscanf.html"><span class="t-lines"><span>vscanf</span><span>vfscanf</span><span>vsscanf</span></span></a></div>
|
||||
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
|
||||
</div>
|
||||
</td>
|
||||
<td>使用可变实参列表<br />
|
||||
从 <span class="t-lc"><a href="cpp-io-c.html">stdin</a></span>、文件流或缓冲区读取有格式输入<br />
|
||||
<span class="t-mark">(函数)</span></td>
|
||||
</tr>
|
||||
<tr class="t-dsc">
|
||||
<td>
|
||||
<div class="t-dsc-member-div">
|
||||
<div><a href="cpp-io-c-fgets.html"><span class="t-lines"><span>fgets</span></span></a></div>
|
||||
</div>
|
||||
</td>
|
||||
<td>从文件流获取字符串<br />
|
||||
<span class="t-mark">(函数)</span></td>
|
||||
</tr>
|
||||
<tr class="t-dsc">
|
||||
<td>
|
||||
<div class="t-dsc-member-div">
|
||||
<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>
|
||||
<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>
|
||||
</div>
|
||||
</td>
|
||||
<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>
|
||||
</tr>
|
||||
<tr class="t-dsc">
|
||||
<td>
|
||||
<div class="t-dsc-member-div">
|
||||
<div><a href="cpp-utility-from_chars.html"><span class="t-lines"><span>from_chars</span></span></a></div>
|
||||
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
|
||||
</div>
|
||||
</td>
|
||||
<td>转换字符序列到整数或浮点值<br />
|
||||
<span class="t-mark">(函数)</span></td>
|
||||
</tr>
|
||||
</table>
|
||||
</div>
|
||||
<div class="visualClear"></div>
|
||||
</div>
|
||||
</div>
|
||||
</div>
|
||||
</body>
|
||||
</html>
|
||||
Reference in New Issue
Block a user