123 lines
7.4 KiB
HTML
123 lines
7.4 KiB
HTML
<!DOCTYPE html>
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<title>std::timespec_get</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_chrono_c_timespec_get 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>timespec_get</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-chrono.html">chrono</a>‎ | <a href="cpp-chrono-c.html">c</a></span></div>
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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-ctime.html"><ctime></a></code></div>
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<td></td>
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<td></td>
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<tr class="t-dcl t-since-cxx17">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> timespec_get<span class="br0">(</span> <a href="cpp-chrono-c-timespec.html"><span class="kw1024">std::<span class="me2">timespec</span></span></a><span class="sy2">*</span> ts, <span class="kw4">int</span> base <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><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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<tr class="t-dcl t-since-cxx17">
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<div><span class="mw-geshi cpp source-cpp"><span class="co2">#define TIME_UTC /* implementation-defined */</span></span></div>
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<td>(2)</td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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<div class="t-li1"><span class="t-li">1)</span> 修改 <code>ts</code> 所指向的 <span class="t-lc"><a href="cpp-chrono-c-timespec.html">std::timespec</a></span> 对象,以保有时间基底 <code>base</code> 中的当前日历时间。</div>
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<div class="t-li1"><span class="t-li">2)</span> 展开成适合用作 <code>std::timespec_get</code> 的 <code>base</code> 参数的值。</div>
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<p>实现可提供其他以 <code>TIME_</code> 起始的宏常量,以指示另外的时间基底。</p>
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<p>若 <code>base</code> 为 <code>TIME_UTC</code> ,则</p>
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<ul>
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<li>设 <code>ts->tv_sec</code> 为从实现定义的纪元开始的秒数,截断到整数值</li>
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<li>设 <code>ts->tv_nsec</code> 成员为纳秒的整数,取整到系统时钟的分辨率</li>
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</ul>
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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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<td>ts</td>
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<td>-</td>
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<td>指向 <span class="t-lc"><a href="cpp-chrono-c-timespec.html">std::timespec</a></span> 类型对象的指针</td>
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</tr>
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<tr class="t-par">
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<td>base</td>
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<td>-</td>
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<td><code>TIME_UTC</code> 或另一指示时间基底的非零整数值</td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<p>若成功则为 <code>base</code> 的值,否则为零。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<p>POSIX 函数 <a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_getres.html">clock_gettime(CLOCK_REALTIME, ts)</a> 亦可用于将从纪元开始的时间植入 <code>std::timespec</code> 。</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="t-example">
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<div class="t-example-live-link"></div>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <cstdio></span>
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<span class="co2">#include <ctime></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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<a href="cpp-chrono-c-timespec.html"><span class="kw1024">std::<span class="me2">timespec</span></span></a> ts<span class="sy4">;</span>
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std<span class="sy4">::</span><span class="me2">timespec_get</span><span class="br0">(</span><span class="sy3">&</span>ts, TIME_UTC<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">char</span> buff<span class="br0">[</span><span class="nu0">100</span><span class="br0">]</span><span class="sy4">;</span>
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<a href="cpp-chrono-c-strftime.html"><span class="kw1015">std::<span class="me2">strftime</span></span></a><span class="br0">(</span>buff, sizeof buff, <span class="st0">"%D %T"</span>, <a href="cpp-chrono-c-gmtime.html"><span class="kw1017">std::<span class="me2">gmtime</span></span></a><span class="br0">(</span><span class="sy3">&</span>ts.<span class="me1">tv_sec</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-c-fprintf.html"><span class="kw1843">std::<span class="me2">printf</span></span></a><span class="br0">(</span><span class="st0">"Current time: %s.%09ld UTC<span class="es1">\n</span>"</span>, buff, ts.<span class="me1">tv_nsec</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">Current time: 06/24/16 20:07:42.949494132 UTC</pre></div>
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</div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-c-timespec.html"><span class="t-lines"><span>timespec</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
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</div>
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</td>
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<td>以秒和纳秒表示的时间<br />
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<span class="t-mark">(结构体)</span></td>
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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="cpp-chrono-c-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>返回自纪元起计的系统当前时间<br />
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<span class="t-mark">(函数)</span></td>
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</table>
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</div>
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<div class="visualClear"></div>
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</body>
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