108 lines
8.3 KiB
HTML
108 lines
8.3 KiB
HTML
<!DOCTYPE html>
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<title>std::system_category</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_error_system_category 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>system_category</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-error.html">error</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-system_error.html"><system_error></a></code></div>
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<td></td>
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<tr class="t-dcl t-since-cxx11">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">const</span> <a href="cpp-error-error_category.html"><span class="kw871">std::<span class="me2">error_category</span></span></a><span class="sy3">&</span> system_category<span class="br0">(</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<p>获得到为操作系统报告错误而设的静态错误类别对象的引用。要求对象覆写虚函数 <span class="t-lc"><a href="cpp-error-error_category-name.html">std::error_category::name()</a></span> 以返回指向字符串 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"system"</span></span></span> 的指针。亦要求重写虚函数 <span class="t-lc"><a href="cpp-error-error_category-default_error_condition.html">std::error_category::default_error_condition()</a></span> 以映射匹配 POSIX <span class="t-lc"><a href="cpp-error-errno.html">errno</a></span> 值的 error_code 到 <span class="t-lc"><a href="cpp-error-generic_category.html">std::generic_category</a></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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<p>（无）</p>
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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>到从 <span class="t-lc"><a href="cpp-error-error_category.html">std::error_category</a></span> 派生的未指定运行时类型的静态对象的引用。</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 <iostream></span>
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<span class="co2">#include <system_error></span>
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<span class="co2">#include <iomanip></span>
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<span class="co2">#include <string></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-error-error_condition.html"><span class="kw873">std::<span class="me2">error_condition</span></span></a> econd <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">system_category</span><span class="br0">(</span><span class="br0">)</span>.<span class="me1">default_error_condition</span><span class="br0">(</span><a href="cpp-error-errno_macros.html"><span class="kw810">EDOM</span></a><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">"Category: "</span> <span class="sy1"><<</span> econd.<span class="me1">category</span><span class="br0">(</span><span class="br0">)</span>.<span class="me1">name</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
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<span class="sy1"><<</span> <span class="st0">"Value: "</span> <span class="sy1"><<</span> econd.<span class="me1">value</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
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<span class="sy1"><<</span> <span class="st0">"Message: "</span> <span class="sy1"><<</span> econd.<span class="me1">message</span><span class="br0">(</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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econd <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">system_category</span><span class="br0">(</span><span class="br0">)</span>.<span class="me1">default_error_condition</span><span class="br0">(</span><span class="nu0">10001</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">"Category: "</span> <span class="sy1"><<</span> econd.<span class="me1">category</span><span class="br0">(</span><span class="br0">)</span>.<span class="me1">name</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
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<span class="sy1"><<</span> <span class="st0">"Value: "</span> <span class="sy1"><<</span> econd.<span class="me1">value</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
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<span class="sy1"><<</span> <span class="st0">"Message: "</span> <span class="sy1"><<</span> econd.<span class="me1">message</span><span class="br0">(</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>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">Category: generic
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Value: 33
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Message: Numerical argument out of domain
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Category: system
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Value: 10001
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Message: Unknown error 10001</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-error-generic_category.html"><span class="t-lines"><span>generic_category</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>鉴别通用错误类别<br />
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<span class="t-mark">(函数)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-error-errc.html"><span class="t-lines"><span>errc</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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<td>列出所有标准 <a href="cpp-header-cerrno.html"><tt><cerrno></tt></a> 宏常量的 <span class="t-lc"><a href="cpp-error-error_condition.html">std::error_condition</a></span> 枚举<br />
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<span class="t-mark">(类)</span></td>
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<div class="visualClear"></div>
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