174 lines
17 KiB
HTML
174 lines
17 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::filesystem::u8path</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_filesystem_path_u8path 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::filesystem::</span>u8path</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-filesystem.html">filesystem</a>‎ | <a href="cpp-filesystem-path.html">path</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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<td>
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<div>定义于头文件 <code><a href="cpp-header-filesystem.html"><filesystem></a></code></div>
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</td>
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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="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Source <span class="sy1">></span><br />
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<a href="cpp-filesystem-path.html"><span class="kw2199">std::<span class="me2">filesystem</span><span class="sy4">::</span><span class="me2">path</span></span></a> u8path<span class="br0">(</span> <span class="kw4">const</span> Source<span class="sy3">&</span> source <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><br />
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<span class="t-mark">(C++20 中弃用)</span></td>
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</tr>
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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="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> InputIt <span class="sy1">></span><br />
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<a href="cpp-filesystem-path.html"><span class="kw2199">std::<span class="me2">filesystem</span><span class="sy4">::</span><span class="me2">path</span></span></a> u8path<span class="br0">(</span> InputIt first, InputIt last <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><span class="t-mark-rev t-since-cxx17">(C++17 起)</span><br />
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<span class="t-mark">(C++20 中弃用)</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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<p>从 UTF-8 编码的 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char</span></span></span> <span class="t-rev-inl t-since-cxx20"><span>或 <span class="t-c"><span class="mw-geshi cpp source-cpp">char8_t</span></span></span> <span><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></span></span> 序列构造 path <code>p</code> ，源作为 <span class="t-lc"><a href="cpp-string-basic_string.html">std::string</a></span> 或 <span class="t-lc"><a href="cpp-string-basic_string_view.html">std::string_view</a></span> ，或空终止多字节字符串，或作为一对迭代器 [first, last) 提供。</p>
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<ul>
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<li>若 <code>path::value_type</code> 是 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char</span></span></span> 且原生编码为 UTF-8 ，则直接如同以 <span class="t-c"><span class="mw-geshi cpp source-cpp">path<span class="br0">(</span>source<span class="br0">)</span></span></span> 或 <span class="t-c"><span class="mw-geshi cpp source-cpp">path<span class="br0">(</span>first, last<span class="br0">)</span></span></span> 构造 path 。这是使用 Unicode 的 POSIX 系统的典型情况，例如 Linux 。</li>
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<li>否则，若 <code>path::value_type</code> 是 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">wchar_t</span></span></span> 且原生编码是 UTF-16 （这是 Windows 上的情况），或若 <code>path::value_type</code> 是 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char16_t</span></span></span> （原生编码保证为 UTF-16 ）或 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char32_t</span></span></span> （原生编码保证为</li>
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</ul>
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<p>UTF-32），则首先转换 UTF-8 字符序列为 <code>path::string_type</code> 类型的临时字符串 <code>tmp</code> ，然后如同以 <span class="t-c"><span class="mw-geshi cpp source-cpp">path<span class="br0">(</span>tmp<span class="br0">)</span></span></span> 构造新 path</p>
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<ul>
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<li>否则（对于非 UTF-8 窄字符编码与非 UTF-16 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">wchar_t</span></span></span> ），首先转换 UTF-8 字符序列到 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-string-basic_string.html"><span class="kw1236">std::<span class="me2">u32string</span></span></a></span></span> 类型的临时 UTF-32 编码字符串 <code>tmp</code> ，然后如同用 <span class="t-c"><span class="mw-geshi cpp source-cpp">path<span class="br0">(</span>tmp<span class="br0">)</span></span></span> 构造新 path （此 path 被采用于使用非 Unicode 多字节或单字节编码的文件系统的 POSIX 系统上）</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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<tr class="t-par">
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<td>source</td>
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<td>-</td>
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<td>UTF-8 编码的 <span class="t-lc"><a href="cpp-string-basic_string.html">std::string</a></span> 、 <span class="t-lc"><a href="cpp-string-basic_string_view.html">std::string_view</a></span> ，指向空终止多字节字符串的指针，或指向空终止多字节字符串的以 char 为 value_type 的输入迭代器</td>
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</tr>
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<tr class="t-par">
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<td>first, last</td>
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<td>-</td>
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<td>一对指定 UTF-8 编码字符序列的<a href="cpp-named_req-InputIterator.html"><span style="font-style:italic">老式输入迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyInputIterator)</span></a></td>
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</tr>
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<tr class="t-par-hitem">
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<td colspan="3">类型要求</td>
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</tr>
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<tr class="t-par-req">
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<td colspan="3">-
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<div class="spacer"></div>
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<code>InputIt</code> 必须满足<a href="cpp-named_req-InputIterator.html"><span style="font-style:italic">老式输入迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyInputIterator)</span></a> 的要求。</td>
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</tr>
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<tr class="t-par-req">
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<td colspan="3">-
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<div class="spacer"></div>
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<code>Source</code> 或 <code>InputIt</code> 的值类型必须是 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char</span></span></span> <span class="t-rev-inl t-since-cxx20"><span>或 <span class="t-c"><span class="mw-geshi cpp source-cpp">char8_t</span></span></span> <span><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></span></span></td>
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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>将输入字符串从 UTF-8 转换到文件系统原生字符编码后，构造的路径。</p>
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<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">异常</span></h3>
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<p>若内存分配失败则可能抛出 <span class="t-lc"><a href="cpp-memory-new-bad_alloc.html">std::bad_alloc</a></span> 。</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>在原生路径格式异于通用路径格式的系统上（ Windows 与 POSIX 均不是此种系统的例子），若此函数的参数使用通用格式，则它会被转换成原生格式。</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">#ifdef _MSC_VER</span>
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<span class="co2">#include <io.h></span>
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<span class="co2">#include <fcntl.h></span>
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<span class="co2">#else</span>
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<span class="co2">#include <locale></span>
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<span class="co2">#include <clocale></span>
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<span class="co2">#endif</span>
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<span class="co2">#include <fstream></span>
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<span class="co2">#include <iostream></span>
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<span class="co2">#include <filesystem></span>
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<span class="kw1">namespace</span> fs <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">filesystem</span><span class="sy4">;</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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<span class="co2">#ifdef _MSC_VER</span>
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_setmode<span class="br0">(</span>_fileno<span class="br0">(</span><span class="kw2">stderr</span><span class="br0">)</span>, _O_WTEXT<span class="br0">)</span><span class="sy4">;</span>
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<span class="co2">#else</span>
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<a href="cpp-locale-setlocale.html"><span class="kw1990">std::<span class="me2">setlocale</span></span></a><span class="br0">(</span><a href="cpp-locale-LC_categories.html"><span class="kw1993">LC_ALL</span></a>, <span class="st0">""</span><span class="br0">)</span><span class="sy4">;</span>
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std<span class="sy4">::</span><span class="me2">locale</span><span class="sy4">::</span><span class="me2">global</span><span class="br0">(</span><a href="cpp-locale-locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="st0">""</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="kw1758">std::<span class="me2">cout</span></span></a>.<span class="me1">imbue</span><span class="br0">(</span><a href="cpp-locale-locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cerr.html"><span class="kw1761">std::<span class="me2">wcerr</span></span></a>.<span class="me1">imbue</span><span class="br0">(</span><a href="cpp-locale-locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="co2">#endif</span>
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fs<span class="sy4">::</span><span class="me2">path</span> p <span class="sy1">=</span> fs<span class="sy4">::</span><span class="me2">u8path</span><span class="br0">(</span>u8<span class="st0">"要らない.txt"</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-basic_ofstream.html"><span class="kw1733">std::<span class="me2">ofstream</span></span></a><span class="br0">(</span>p<span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">"File contents"</span><span class="sy4">;</span> <span class="co1">// 在 LWG2676 前 MSVC 上使用 operator string_type()</span>
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<span class="co1">// ，其中 string_type 是 wstring ，仅根据非标准扩展工作</span>
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<span class="co1">// LWG2676 后使用新的 fstream 构造函数</span>
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<span class="co1">// 原生字符串表示可用于 OS API</span>
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<span class="kw1">if</span> <span class="br0">(</span><a href="cpp-io-c.html"><span class="kw1877">std::<span class="me2">FILE</span></span></a><span class="sy2">*</span> f <span class="sy1">=</span>
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<span class="co2">#ifdef _MSC_VER</span>
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_wfopen<span class="br0">(</span>p.<span class="me1">c_str</span><span class="br0">(</span><span class="br0">)</span>, L<span class="st0">"r"</span><span class="br0">)</span>
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<span class="co2">#else</span>
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<a href="cpp-io-c-fopen.html"><span class="kw1813">std::<span class="me2">fopen</span></span></a><span class="br0">(</span>p.<span class="me1">c_str</span><span class="br0">(</span><span class="br0">)</span>, <span class="st0">"r"</span><span class="br0">)</span>
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<span class="co2">#endif</span>
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<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw4">int</span> ch<span class="sy4">;</span>
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<span class="kw1">while</span><span class="br0">(</span><span class="br0">(</span>ch<span class="sy1">=</span>fgetc<span class="br0">(</span>f<span class="br0">)</span><span class="br0">)</span><span class="sy3">!</span><span class="sy1">=</span> <a href="cpp-io-c.html"><span class="kw1882">EOF</span></a><span class="br0">)</span> putchar<span class="br0">(</span>ch<span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-c-fclose.html"><span class="kw1816">std::<span class="me2">fclose</span></span></a><span class="br0">(</span>f<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="co1">// 多字节与宽字节表示可用于输出</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"<span class="es1">\n</span>File name in narrow multibyte encoding: "</span> <span class="sy1"><<</span> p.<span class="me1">string</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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<a href="cpp-io-cerr.html"><span class="kw1761">std::<span class="me2">wcerr</span></span></a> <span class="sy1"><<</span> <span class="st0">"File name in wide encoding: "</span> <span class="sy1"><<</span> p.<span class="me1">wstring</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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fs<span class="sy4">::</span><span class="me2">remove</span><span class="br0">(</span>p<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>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">File contents
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File name in narrow multibyte encoding: 要らない.txt
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File name in wide encoding: 要らない.txt</pre></div>
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</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-filesystem-path.html"><span class="t-lines"><span>path</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>表示路径<br />
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<span class="t-mark">(类)</span></td>
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</tr>
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</table>
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</div>
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<div class="visualClear"></div>
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</div>
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