102 lines
8.5 KiB
HTML
102 lines
8.5 KiB
HTML
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<title>std::localtime</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_chrono_c_localtime skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>localtime</h1>
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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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<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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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-chrono-c-tm.html"><span class="kw1022">std::<span class="me2">tm</span></span></a><span class="sy2">*</span> localtime<span class="br0">(</span> <span class="kw4">const</span> <a href="cpp-chrono-c-time_t.html"><span class="kw1023">std::<span class="me2">time_t</span></span></a> <span class="sy2">*</span>time <span class="br0">)</span><span class="sy4">;</span></span></div>
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<p>转换作为 <span class="t-lc"><a href="cpp-chrono-c-time_t.html">std::time_t</a></span> 值的从纪元起时间到以本地时间表达的日历时。</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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<td>time</td>
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<td>-</td>
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<td>指向要转换的 time_t 对象的指针</td>
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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>成功时为指向内部静态 <span class="t-lc"><a href="cpp-chrono-c-tm.html">std::tm</a></span> 对象的指针，否则为 <span class="t-lc"><a href="cpp-types-NULL.html">NULL</a></span> 。该结构体可能在 <span class="t-lc"><a href="cpp-chrono-c-gmtime.html">std::gmtime</a></span> 、 <span class="t-lc"><strong class="selflink">std::localtime</strong></span> 和 <span class="t-lc"><a href="cpp-chrono-c-ctime.html">std::ctime</a></span> 之间共享，而且可能在每次调用时被覆盖。</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>此函数可能不是线程安全的。</p>
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<p>POSIX 要求若此函数因参数过大而失败，则设置 <span class="t-lc"><a href="cpp-error-errno.html">errno</a></span> 为 <span class="t-lc"><a href="cpp-error-errno_macros.html">EOVERFLOW</a></span> 。</p>
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<p><a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/localtime.html">POSIX 指定</a>此函数如同以调用 <a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/tzset.html">tzset</a> 确定时区信息，该函数调用环境变量 <span class="t-c"><span class="mw-geshi cpp source-cpp">TZ</span></span> 。</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <iostream></span>
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<span class="co2">#include <iomanip></span>
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<span class="co2">#include <ctime></span>
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<span class="co2">#include <stdlib.h> // 定义 putenv 于 POSIX</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-time_t.html"><span class="kw1023">std::<span class="me2">time_t</span></span></a> t <span class="sy1">=</span> <a href="cpp-chrono-c-time.html"><span class="kw1011">std::<span class="me2">time</span></span></a><span class="br0">(</span>nullptr<span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"UTC: "</span> <span class="sy1"><<</span> <a href="cpp-io-manip-put_time.html"><span class="kw1800">std::<span class="me2">put_time</span></span></a><span class="br0">(</span><a href="cpp-chrono-c-gmtime.html"><span class="kw1019">std::<span class="me2">gmtime</span></span></a><span class="br0">(</span><span class="sy3">&</span>t<span class="br0">)</span>, <span class="st0">"%c %Z"</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"local: "</span> <span class="sy1"><<</span> <a href="cpp-io-manip-put_time.html"><span class="kw1800">std::<span class="me2">put_time</span></span></a><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">localtime</span><span class="br0">(</span><span class="sy3">&</span>t<span class="br0">)</span>, <span class="st0">"%c %Z"</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="co1">// POSIX 限定：</span>
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<a href="cpp-string-basic_string.html"><span class="kw1229">std::<span class="me2">string</span></span></a> tz <span class="sy1">=</span> <span class="st0">"TZ=Asia/Singapore"</span><span class="sy4">;</span>
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putenv<span class="br0">(</span>tz.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Singapore: "</span> <span class="sy1"><<</span> <a href="cpp-io-manip-put_time.html"><span class="kw1800">std::<span class="me2">put_time</span></span></a><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">localtime</span><span class="br0">(</span><span class="sy3">&</span>t<span class="br0">)</span>, <span class="st0">"%c %Z"</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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<p>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">UTC: Fri Sep 15 14:16:29 2017 GMT
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local: Fri Sep 15 14:16:29 2017 UTC
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Singapore: Fri Sep 15 22:16:29 2017 SGT</pre></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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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-c-gmtime.html"><span class="t-lines"><span>gmtime</span></span></a></div>
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</div>
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</td>
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<td>转换纪元起时间为以协调世界时表示的日历时间<br />
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<span class="t-mark">(函数)</span></td>
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<div class="visualClear"></div>
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