675 lines
57 KiB
HTML
675 lines
57 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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<title>std::printf, std::fprintf, std::sprintf, std::snprintf</title>
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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_fprintf 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>printf, <span style="font-size:0.7em; line-height:130%">std::</span>fprintf, <span style="font-size:0.7em; line-height:130%">std::</span>sprintf, <span style="font-size:0.7em; line-height:130%">std::</span>snprintf</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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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> printf<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> fprintf<span class="br0">(</span> <a href="cpp-io-c.html"><span class="kw1873">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 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> sprintf<span class="br0">(</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 t-since-cxx11">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> snprintf<span class="br0">(</span> <span class="kw4">char</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> buf_size, <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>(4)</td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></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，转换为字符串等价版本，并将结果写入各种池。</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> 写结果到字符串 <code>buffer</code> 。</div>
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<div class="t-li1"><span class="t-li">4)</span> 写结果到字符串 <code>buffer</code> 。至多写 <code>buf_size</code> - 1 个字符。产生的字符串会以空字符终止，除非 <code>buf_size</code> 为零。若 <code>buf_size</code> 为零，则不写入任何内容，且 <code>buffer</code> 可以是空指针，然而依旧计算返回值（会写入的字符数，不包含空终止符）并返回。</div>
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<p>若调用 <code>sprintf</code> 或 <code>snprintf</code> 导致在重叠的对象间发生复制，则行为未定义。（例如 <span class="t-c"><span class="mw-geshi cpp source-cpp">sprintf<span class="br0">(</span>buf, <span class="st0">"%s text"</span>, buf<span class="br0">)</span><span class="sy4">;</span></span></span> ）</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<table class="t-par-begin">
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<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>buf_size</td>
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<td>-</td>
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<td>写入至多 buf_size - 1 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>指向指定如何转译数据的空终止多字节字符串的指针。
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<p>格式字符串由普通多字节字符（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">unsigned</span> <span class="kw4">char</span></span></span> 。 若使用 <b>l</b> 修饰符，则参数首先被转换成字符串，如同通过以 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">wchar_t</span><span class="br0">[</span><span class="nu0">2</span><span class="br0">]</span></span></span> 参数使用 <b>%ls</b> 。</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>参数必须是指向字符数组首元素的指针 <i>精度</i>指定写入最大的字符数。若未指定<i>精度</i>，则写每个字节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，数组会被转换成 char 数组，如同通过以零初始化转换状态调用 <span class="t-lc">wcrtomb</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">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>
|
|
</div>
|
|
</td>
|
|
<td rowspan="1">
|
|
<div class="t-vertical">
|
|
<div>有符号 <span class="t-c"><span class="mw-geshi cpp source-cpp">size_t</span></span></div>
|
|
</div>
|
|
</td>
|
|
<td rowspan="1">
|
|
<div class="t-vertical">
|
|
<div><span class="t-c"><span class="mw-geshi cpp source-cpp">ptrdiff_t</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>o</code></th>
|
|
<td style="text-align:left;">
|
|
<dl>
|
|
<dd>转换<b>无符号整数</b>为八进制表示 <i>oooo</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。 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>
|
|
<p>若转换指定非法，则行为未定义。</p>
|
|
<p><br /></p>
|
|
</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>...</td>
|
|
<td>-</td>
|
|
<td>指定要打印数据的参数。若任何参数类型不是对应转换指定符所期望者，或若参数数量少于 <code>format</code> 所要求这，则行为未定义。若参数数量多于 <code>format</code> 所要求者，则求值后忽略额外参数</td>
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</tr>
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</table>
|
|
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
|
|
<div class="t-li1"><span class="t-li">1-2)</span> 若成功则为写入的字符数，若发生错误则为负值。</div>
|
|
<div class="t-li1"><span class="t-li">3)</span> 若成功则为写入的字符数（不包含空终止字符），若发生错误则为负值。</div>
|
|
<div class="t-li1"><span class="t-li">4)</span> 若成功则为会写入充分大缓冲区的字符数（不包含空终止字符），若发生错误则为负值。从而，当且仅当返回值非负且小于 <code>buf_size</code> 才完全写入（空终止）。</div>
|
|
<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">注意</span></h3>
|
|
<p><a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/fprintf.html">POSIX 规定</a>在错误时设置 <span class="t-lc"><a href="cpp-error-errno.html">errno</a></span> 。它亦指定额外的转换指定，最值得注意的是对参数重排序的支持（紧随 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">%</span></span></span> 后的 <span class="t-c"><span class="mw-geshi cpp source-cpp">n$</span></span> 指示第 <code>n</code> 个参数）。</p>
|
|
<p>以零 <code>buf_size</code> 和对于 <code>buffer</code> 的空指针调用 <code>std::snprintf</code> 适用于确定容纳输出的所需缓冲区大小：</p>
|
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
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<pre class="de1"><span class="kw4">const</span> <span class="kw4">char</span> <span class="sy2">*</span>fmt <span class="sy1">=</span> <span class="st0">"sqrt(2) = %f"</span><span class="sy4">;</span>
|
|
<span class="kw4">int</span> sz <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">snprintf</span><span class="br0">(</span>nullptr, <span class="nu0">0</span>, fmt, <a href="cpp-numeric-math-sqrt.html"><span class="kw1329">std::<span class="me2">sqrt</span></span></a><span class="br0">(</span><span class="nu0">2</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-container-vector.html"><span class="kw1269">std::<span class="me2">vector</span></span></a><span class="sy1"><</span><span class="kw4">char</span><span class="sy1">></span> buf<span class="br0">(</span>sz <span class="sy2">+</span> <span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 注意为空终止符 +1</span>
|
|
std<span class="sy4">::</span><span class="me2">snprintf</span><span class="br0">(</span><span class="sy3">&</span>buf<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span>, buf.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span>, fmt, <a href="cpp-numeric-math-sqrt.html"><span class="kw1329">std::<span class="me2">sqrt</span></span></a><span class="br0">(</span><span class="nu0">2</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</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 <cstdio></span>
|
|
<span class="co2">#include <limits></span>
|
|
<span class="co2">#include <cstdint></span>
|
|
<span class="co2">#include <cinttypes></span>
|
|
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"Strings:<span class="es1">\n</span>"</span><span class="br0">)</span><span class="sy4">;</span>
|
|
|
|
<span class="kw4">const</span> <span class="kw4">char</span><span class="sy2">*</span> s <span class="sy1">=</span> <span class="st0">"Hello"</span><span class="sy4">;</span>
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"<span class="es1">\t</span>[%10s]<span class="es1">\n</span><span class="es1">\t</span>[%-10s]<span class="es1">\n</span><span class="es1">\t</span>[%*s]<span class="es1">\n</span><span class="es1">\t</span>[%-10.*s]<span class="es1">\n</span><span class="es1">\t</span>[%-*.*s]<span class="es1">\n</span>"</span>,
|
|
s, s, <span class="nu0">10</span>, s, <span class="nu0">4</span>, s, <span class="nu0">10</span>, <span class="nu0">4</span>, s<span class="br0">)</span><span class="sy4">;</span>
|
|
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"Characters:<span class="es1">\t</span>%c %%<span class="es1">\n</span>"</span>, <span class="nu0">65</span><span class="br0">)</span><span class="sy4">;</span>
|
|
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"Integers<span class="es1">\n</span>"</span><span class="br0">)</span><span class="sy4">;</span>
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"Decimal:<span class="es1">\t</span>%i %d %.6i %i %.0i %+i %u<span class="es1">\n</span>"</span>, <span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu0">3</span>, <span class="nu0">0</span>, <span class="nu0">0</span>, <span class="nu0">4</span>, <span class="sy2">-</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span>
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"Hexadecimal:<span class="es1">\t</span>%x %x %X %#x<span class="es1">\n</span>"</span>, <span class="nu0">5</span>, <span class="nu0">10</span>, <span class="nu0">10</span>, <span class="nu0">6</span><span class="br0">)</span><span class="sy4">;</span>
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"Octal:<span class="es1">\t</span>%o %#o %#o<span class="es1">\n</span>"</span>, <span class="nu0">10</span>, <span class="nu0">10</span>, <span class="nu0">4</span><span class="br0">)</span><span class="sy4">;</span>
|
|
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"Floating point<span class="es1">\n</span>"</span><span class="br0">)</span><span class="sy4">;</span>
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"Rounding:<span class="es1">\t</span>%f %.0f %.32f<span class="es1">\n</span>"</span>, <span class="nu16">1.5</span>, <span class="nu16">1.5</span>, <span class="nu16">1.5</span><span class="br0">)</span><span class="sy4">;</span>
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"Padding:<span class="es1">\t</span>%05.2f %.2f %5.2f<span class="es1">\n</span>"</span>, <span class="nu16">1.5</span>, <span class="nu16">1.5</span>, <span class="nu16">1.5</span><span class="br0">)</span><span class="sy4">;</span>
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"Scientific:<span class="es1">\t</span>%E %e<span class="es1">\n</span>"</span>, <span class="nu16">1.5</span>, <span class="nu16">1.5</span><span class="br0">)</span><span class="sy4">;</span>
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"Hexadecimal:<span class="es1">\t</span>%a %A<span class="es1">\n</span>"</span>, <span class="nu16">1.5</span>, <span class="nu16">1.5</span><span class="br0">)</span><span class="sy4">;</span>
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"Special values:<span class="es1">\t</span>0/0=%g 1/0=%g<span class="es1">\n</span>"</span>, <span class="nu16">0.0</span><span class="sy2">/</span><span class="nu16">0.0</span>, <span class="nu16">1.0</span><span class="sy2">/</span><span class="nu16">0.0</span><span class="br0">)</span><span class="sy4">;</span>
|
|
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"Variable width control:<span class="es1">\n</span>"</span><span class="br0">)</span><span class="sy4">;</span>
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"right-justified variable width: '%*c'<span class="es1">\n</span>"</span>, <span class="nu0">5</span>, <span class="st0">'x'</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="kw4">int</span> r <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"left-justified variable width : '%*c'<span class="es1">\n</span>"</span>, <span class="sy2">-</span><span class="nu0">5</span>, <span class="st0">'x'</span><span class="br0">)</span><span class="sy4">;</span>
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"(the last printf printed %d characters)<span class="es1">\n</span>"</span>, r<span class="br0">)</span><span class="sy4">;</span>
|
|
|
|
<span class="co1">// 定宽类型</span>
|
|
<a href="cpp-types-integer.html"><span class="kw122">std::<span class="me2">uint32_t</span></span></a> val <span class="sy1">=</span> <a href="cpp-types-numeric_limits.html"><span class="kw344">std::<span class="me2">numeric_limits</span></span></a><span class="sy1"><</span><a href="cpp-types-integer.html"><span class="kw122">std::<span class="me2">uint32_t</span></span></a><span class="sy1">></span><span class="sy4">::</span><span class="me2">max</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
|
|
std<span class="sy4">::</span><span class="me2">printf</span><span class="br0">(</span><span class="st0">"Largest 32-bit value is %"</span> <a href="cpp-types-integer.html"><span class="kw206">PRIu32</span></a> <span class="st0">" or %#"</span> <a href="cpp-types-integer.html"><span class="kw234">PRIx32</span></a> <span class="st0">"<span class="es1">\n</span>"</span>, val, val<span class="br0">)</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">Strings:
|
|
[ Hello]
|
|
[Hello ]
|
|
[ Hello]
|
|
[Hell ]
|
|
[Hell ]
|
|
Characters: A %
|
|
Integers
|
|
Decimal: 1 2 000003 0 +4 4294967295
|
|
Hexadecimal: 5 a A 0x6
|
|
Octal: 12 012 04
|
|
Floating point
|
|
Rounding: 1.500000 2 1.30000000000000004440892098500626
|
|
Padding: 01.50 1.50 1.50
|
|
Scientific: 1.500000E+00 1.500000e+00
|
|
Hexadecimal: 0x1.8p+0 0X1.8P+0
|
|
Special values: 0/0=nan 1/0=inf
|
|
Variable width control:
|
|
right-justified variable width: ' x'
|
|
left-justified variable width : 'x '
|
|
(the last printf printed 40 characters)
|
|
Largest 32-bit value is 4294967295 or 0xffffffff</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-fwprintf.html"><span class="t-lines"><span>wprintf</span><span>fwprintf</span><span>swprintf</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>打印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>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-io-c-vfprintf.html"><span class="t-lines"><span>vprintf</span><span>vfprintf</span><span>vsprintf</span><span>vsnprintf</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>使用可变实参列表<br />
|
|
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-io-c-fputs.html"><span class="t-lines"><span>fputs</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>写字符串到文件流<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-fscanf.html"><span class="t-lines"><span>scanf</span><span>fscanf</span><span>sscanf</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>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-utility-to_chars.html"><span class="t-lines"><span>to_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>转换整数或浮点值到字符序列<br />
|
|
<span class="t-mark">(函数)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|