193 lines
17 KiB
HTML
193 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::path::string, std::filesystem::path::wstring, std::filesystem::path::u8string, std::filesystem::path::u16string, std::filesystem::path::u32string</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_filesystem_path_string 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::filesystem::path::</span>string, <span style="font-size:0.7em; line-height:130%">std::filesystem::path::</span>wstring, <span style="font-size:0.7em; line-height:130%">std::filesystem::path::</span>u8string, <span style="font-size:0.7em; line-height:130%">std::filesystem::path::</span>u16string, <span style="font-size:0.7em; line-height:130%">std::filesystem::path::</span>u32string</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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<table class="t-dcl-begin">
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<tr class="t-dcl t-since-cxx17">
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<td>
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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> CharT, <span class="kw1">class</span> Traits <span class="sy1">=</span> <a href="cpp-string-char_traits.html"><span class="kw1267">std::<span class="me2">char_traits</span></span></a><span class="sy1"><</span>CharT<span class="sy1">></span>,<br /></span>
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<p> <span class="kw1">class</span> Alloc <span class="sy1">=</span> <a href="cpp-memory-allocator.html"><span class="kw700">std::<span class="me2">allocator</span></span></a><span class="sy1"><</span>CharT<span class="sy1">></span> <span class="sy1">></span><br />
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<a href="cpp-string-basic_string.html"><span class="kw1228">std::<span class="me2">basic_string</span></span></a><span class="sy1"><</span>CharT, Traits, Alloc<span class="sy1">></span><br /></p>
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string<span class="br0">(</span> <span class="kw4">const</span> Alloc<span class="sy3">&</span> a <span class="sy1">=</span> Alloc<span class="br0">(</span><span class="br0">)</span> <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</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>
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</tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num t-dcl-rev-notes t-since-cxx17">
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<td></td>
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<td rowspan="142">(2)</td>
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<td rowspan="142"><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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</tr>
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<tr class="t-dcl">
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> string<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-string-basic_string.html"><span class="kw1232">std::<span class="me2">wstring</span></span></a> wstring<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-string-basic_string.html"><span class="kw1234">std::<span class="me2">u16string</span></span></a> u16string<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<div><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> u32string<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><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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</tbody>
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<tbody></tbody>
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<td></td>
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<td rowspan="142">(3)</td>
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<td></td>
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</tr>
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<tr class="t-dcl t-since-cxx17 t-until-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> u8string<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><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><span class="t-mark-rev t-since-cxx17">(C++17 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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<div><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">u8string</span> u8string<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><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><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody>
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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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</table>
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<p>返回原生路径名格式的内部路径名，转换到指定的字符串类型。若存在转换，则按下列方式进行：</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> ，若转换存在，则转换是依赖系统的。这是在典型 POSIX 系统（例如 Linux ）上的情形，其中原生字符编码是 UTF-8 且 <code>string()</code> 不进行转换。</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> ，若转换存在，则是未指定的。这是在 Windows 上的情形，其中 wchar_t 为 16 位且原生编码为 UTF-16 。</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">char16_t</span></span></span> ，则原生编码是 UTF-16 而转换方法未指定。</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">char32_t</span></span></span> ，则原生编码是 UTF-32 而转换方法未指定。</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">char8_t</span></span> ，则原生编码是 UTF-8 而转换方法未指定。</li>
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</ul>
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<div class="t-li1"><span class="t-li">1)</span> 所有内存分配由 <code>a</code> 进行。</div>
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<div class="t-li1"><span class="t-li">3)</span> <code>u8string()</code> 情形的编码结果始终是 UTF-8 。</div>
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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>转换到指定字符串类型的原生路径名格式的内部路径名。</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>可能抛出实现定义的异常。</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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<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-filesystem-path-generic_string.html"><span class="t-lines"><span>generic_string</span><span>generic_wstring</span><span>generic_u8string</span><span>generic_u16string</span><span>generic_u32string</span></span></a></div>
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</div>
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</td>
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<td>返回转换到字符串的通用路径名格式<br />
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<span class="t-mark">(公开成员函数)</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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</div>
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</div>
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</body>
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</html>
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