152 lines
14 KiB
HTML
152 lines
14 KiB
HTML
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<title>std::filesystem::create_symlink, std::filesystem::create_directory_symlink</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::filesystem::</span>create_symlink, <span style="font-size:0.7em; line-height:130%">std::filesystem::</span>create_directory_symlink</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></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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<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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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span> create_symlink<span class="br0">(</span> <span class="kw4">const</span> <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><span class="sy3">&</span> target,<br /></span>
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<p> <span class="kw4">const</span> <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><span class="sy3">&</span> link <span class="br0">)</span><span class="sy4">;</span><br />
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<span class="kw4">void</span> create_symlink<span class="br0">(</span> <span class="kw4">const</span> <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><span class="sy3">&</span> target,<br />
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<span class="kw4">const</span> <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><span class="sy3">&</span> link,<br /></p>
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<a href="cpp-error-error_code.html"><span class="kw877">std::<span class="me2">error_code</span></span></a><span class="sy3">&</span> ec <span class="br0">)</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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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span> create_directory_symlink<span class="br0">(</span> <span class="kw4">const</span> <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><span class="sy3">&</span> target,<br /></span>
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<p> <span class="kw4">const</span> <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><span class="sy3">&</span> link <span class="br0">)</span><span class="sy4">;</span><br />
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<span class="kw4">void</span> create_directory_symlink<span class="br0">(</span> <span class="kw4">const</span> <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><span class="sy3">&</span> target,<br />
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<span class="kw4">const</span> <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><span class="sy3">&</span> link,<br /></p>
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<a href="cpp-error-error_code.html"><span class="kw877">std::<span class="me2">error_code</span></span></a><span class="sy3">&</span> ec <span class="br0">)</span><span class="sy4">;</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></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>创建符号链接 <code>link</code> ，其目标设为 <code>target</code> ，如同用 POSIX <a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/symlink.html">symlink()</a> ：路径名 <code>target</code> 可以非法或不存在。</p>
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<p>一些操作系统要求符号链接的创建鉴别该链接是否到目录。可移植的代码应用 <span class="t-v">(2)</span> 创建目录符号链接，而非 <span class="t-v">(1)</span> ，即使 POSIX 系统不作区别。</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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<tr class="t-par">
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<td>target</td>
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<td>-</td>
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<td>指定符号链接所至的路径，不必存在</td>
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</tr>
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<tr class="t-par">
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<td>link</td>
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<td>-</td>
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<td>新符号链接的路径</td>
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</tr>
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<tr class="t-par">
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<td>ec</td>
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<td>-</td>
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<td>不抛出重载中报告错误的输出参数</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>（无）</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>不接受 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-error-error_code.html"><span class="kw877">std::<span class="me2">error_code</span></span></a><span class="sy3">&</span></span></span> 参数的重载在底层 OS API 错误时抛出 <a href="cpp-filesystem-filesystem_error.html"><tt>filesystem_error</tt></a> ，以第一 path 参数 <code>target</code>，第二 path 参数 <code>link</code> 和作为错误码参数的 OS 错误码构造。若 OS API 调用失败，则接受 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-error-error_code.html"><span class="kw877">std::<span class="me2">error_code</span></span></a><span class="sy3">&</span></span></span> 参数的重载设置该参数为 OS API 错误码，而若不出现错误则执行 <span class="t-c"><span class="mw-geshi cpp source-cpp">ec.<span class="me1">clear</span><span class="br0">(</span><span class="br0">)</span></span></span> 。若内存分配失败，则任何不标记为 <code>noexcept</code> 的重载可能抛出 <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.E6.84.8F">注意</span></h3>
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<p>一些操作系统完全不支持符号链接，或对常规文件支持。</p>
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<p>某些文件系统不支持符号链接，无关乎操作系统，例如用于某些内存卡和闪存驱动器的 FAT 系统。</p>
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<p>类似硬链接，符号链接允许一个文件拥有多个逻辑名。硬链接的存在保证文件的存在，即使原始文件名被移除。符号链接无这种保障；实际上， <code>target</code> 参数所指名的文件不必在链接创建时存在。符号链接能跨越文件系统边界。</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 <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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fs<span class="sy4">::</span><span class="me2">create_directories</span><span class="br0">(</span><span class="st0">"sandbox/subdir"</span><span class="br0">)</span><span class="sy4">;</span>
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fs<span class="sy4">::</span><span class="me2">create_symlink</span><span class="br0">(</span><span class="st0">"target"</span>, <span class="st0">"sandbox/sym1"</span><span class="br0">)</span><span class="sy4">;</span>
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fs<span class="sy4">::</span><span class="me2">create_directory_symlink</span><span class="br0">(</span><span class="st0">"subdir"</span>, <span class="st0">"sandbox/sym2"</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">for</span><span class="br0">(</span><span class="kw4">auto</span> it <span class="sy1">=</span> fs<span class="sy4">::</span><span class="me2">directory_iterator</span><span class="br0">(</span><span class="st0">"sandbox"</span><span class="br0">)</span><span class="sy4">;</span> it <span class="sy3">!</span><span class="sy1">=</span> fs<span class="sy4">::</span><span class="me2">directory_iterator</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="sy2">++</span>it<span class="br0">)</span>
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<span class="kw1">if</span><span class="br0">(</span>is_symlink<span class="br0">(</span>it<span class="sy2">-</span><span class="sy1">></span>symlink_status<span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="br0">)</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="sy2">*</span>it <span class="sy1"><<</span> <span class="st0">"->"</span> <span class="sy1"><<</span> read_symlink<span class="br0">(</span><span class="sy2">*</span>it<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_all</span><span class="br0">(</span><span class="st0">"sandbox"</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">"sandbox/sym1"->"target"
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"sandbox/sym2"->"subdir"</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-status.html"><span class="t-lines"><span>status</span><span>symlink_status</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><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>确定文件属性<br />
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确定文件属性，检查符号链接目标<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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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-read_symlink.html"><span class="t-lines"><span>read_symlink</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>获得符号链接的目标<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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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-create_hard_link.html"><span class="t-lines"><span>create_hard_link</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>创建一个硬链接<br />
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<span class="t-mark">(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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</body>
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