143 lines
6.8 KiB
HTML
143 lines
6.8 KiB
HTML
<!DOCTYPE html>
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<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>time_t</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-c_chrono_time_t 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">time_t</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="c.html">c</a>‎ | <a href="c-chrono.html">chrono</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><time.h></code></div>
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</td>
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<td></td>
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<td></td>
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</tr>
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<tr class="t-dcl">
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<td class="t-dcl-nopad">
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<div><span class="mw-geshi c source-c"><span class="kw1">typedef</span> <span class="coMULTI">/* unspecified */</span> time_t<span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td class="t-dcl-nopad"></td>
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<tr class="t-dcl-sep">
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<td></td>
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<td></td>
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<td></td>
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</tr>
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</tbody>
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</table>
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<p>足以表示时间的<span class="t-rev-inl t-until-c11"><span>算术</span> <span><span class="t-mark-rev t-until-c11">(C11 前)</span></span></span><span class="t-rev-inl t-since-c11"><span>实数</span> <span><span class="t-mark-rev t-since-c11">(C11 起)</span></span></span>类型。</p>
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<p>尽管 C 标准没有定义，它几乎总是一个保有从 UTC 1970 年 1 月 1 日 00:00 开始秒数的整数值（不计闰秒），对应 <a href="https://en.wikipedia.org/wiki/Unix_time" class="extiw" title="enwiki:Unix time">POSIX 时间</a>。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">注意</span></h3>
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<p>标准在提及 <span class="t-lc"><strong class="selflink">time_t</strong></span> 类型值时使用用语<i>日历时间</i>。</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="t-example">
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<p>显示纪元起点。</p>
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<div class="t-example-live-link"></div>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="c source-c">
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<pre class="de1"><span class="co2">#include <stdint.h></span>
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<span class="co2">#include <stdio.h></span>
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<span class="co2">#include <time.h></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
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<span class="br0">{</span>
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time_t epoch <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span>
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<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"%jd seconds since the epoch began<span class="es1">\n</span>"</span>, <span class="br0">(</span><a href="c-types-integer.html"><span class="kw118">intmax_t</span></a><span class="br0">)</span>epoch<span class="br0">)</span><span class="sy4">;</span>
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<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"%s"</span>, <a href="c-chrono-asctime.html"><span class="kw515">asctime</span></a><span class="br0">(</span><a href="c-chrono-gmtime.html"><span class="kw519">gmtime</span></a><span class="br0">(</span><span class="sy3">&</span>epoch<span class="br0">)</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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<p>可能的输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">0 seconds since the epoch began
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Thu Jan 1 00:00:00 1970</pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">引用</span></h3>
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<div class="t-ref-std-11">
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<ul>
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<li>C11 标准（ISO/IEC 9899:2011）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>7.27.1/3 Components of time (p: 388)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c99">
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<ul>
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<li>C99 标准（ISO/IEC 9899:1999）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>7.23.1/3 Components of time (p: 338)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c89">
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<ul>
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<li>C89/C90 标准（ISO/IEC 9899:1990）：</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>4.12.1 Components of time</li>
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</ul>
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</dd>
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</dl>
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</div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="c-chrono-time.html"><span class="t-lines"><span>time</span></span></a></div>
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</div>
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</td>
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<td>返回纪元开始经过的当前系统日历时间<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="c-chrono-localtime.html"><span class="t-lines"><span>localtime</span><span>localtime_r</span><span>localtime_s</span></span></a></div>
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<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c23">(C23)</span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div>
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</div>
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</td>
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<td>将从纪元开始的时间转换成以本地时间表示的日历时间<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="c-chrono-gmtime.html"><span class="t-lines"><span>gmtime</span><span>gmtime_r</span><span>gmtime_s</span></span></a></div>
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<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c23">(C23)</span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div>
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</div>
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</td>
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<td>将从纪元开始的时间转换成以协调世界时（UTC）表示的日历时间<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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</table>
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</div>
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</div>
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</div>
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<div class="visualClear"></div>
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</div>
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</div>
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</div>
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</body>
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</html>
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