117 lines
10 KiB
HTML
117 lines
10 KiB
HTML
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<title>std::filesystem::space</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_filesystem_space 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::</span>space</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></td>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-filesystem-space_info.html"><span class="kw2207">std::<span class="me2">filesystem</span><span class="sy4">::</span><span class="me2">space_info</span></span></a> space<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> p<span class="br0">)</span><span class="sy4">;</span><br /></span>
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<p><a href="cpp-filesystem-space_info.html"><span class="kw2207">std::<span class="me2">filesystem</span><span class="sy4">::</span><span class="me2">space_info</span></span></a> space<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> p,<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="kw1">noexcept</span><span class="sy4">;</span></div>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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<p>确定路径名 <code>p</code> 定位于其上的文件系统信息，如同用 POSIX <a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/statvfs.html">statvfs</a></p>
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<p>植入并返回一个 <a href="cpp-filesystem-space_info.html">space_info</a> 类型的对象，从 POSIX <code>struct statvfs</code> 的如下成员设置：</p>
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<ul>
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<li><code>space_info.capacity</code> 如同被设为 <code>f_blocks*f_frsize</code></li>
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<li><code>space_info.free</code> 被设为 <code>f_bfree*f_frsize</code></li>
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<li><code>space_info.available</code> 被设为 <code>f_bavail*f_frsize</code></li>
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<li>任何不能确定的成员被设为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">static_cast</span><span class="sy1"><</span>uintmax_t<span class="sy1">></span><span class="br0">(</span><span class="sy2">-</span><span class="nu0">1</span><span class="br0">)</span></span></span></li>
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</ul>
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<p>不抛出重载在错误时设所有成员为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">static_cast</span><span class="sy1"><</span>uintmax_t<span class="sy1">></span><span class="br0">(</span><span class="sy2">-</span><span class="nu0">1</span><span class="br0">)</span></span></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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<table class="t-par-begin">
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<tr class="t-par">
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<td>p</td>
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<td>-</td>
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<td>要检验的路径</td>
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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>不抛出重载的报告错误的输出参数</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>文件系统信息（ <a href="cpp-filesystem-space_info.html">space_info</a> 对象）</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>p</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>space_info.available 可以小于或等于 space_info.free</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">space_info</span> devi <span class="sy1">=</span> fs<span class="sy4">::</span><span class="me2">space</span><span class="br0">(</span><span class="st0">"/dev/null"</span><span class="br0">)</span><span class="sy4">;</span>
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fs<span class="sy4">::</span><span class="me2">space_info</span> tmpi <span class="sy1">=</span> fs<span class="sy4">::</span><span class="me2">space</span><span class="br0">(</span><span class="st0">"/tmp"</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="sy1"><<</span> <span class="st0">". Capacity Free Available<span class="es1">\n</span>"</span>
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<span class="sy1"><<</span> <span class="st0">"/dev: "</span> <span class="sy1"><<</span> devi.<span class="me1">capacity</span> <span class="sy1"><<</span> <span class="st0">" "</span>
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<span class="sy1"><<</span> devi.<span class="me1">free</span> <span class="sy1"><<</span> <span class="st0">" "</span> <span class="sy1"><<</span> devi.<span class="me1">available</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">"/tmp: "</span> <span class="sy1"><<</span> tmpi.<span class="me1">capacity</span> <span class="sy1"><<</span> <span class="st0">" "</span>
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<span class="sy1"><<</span> tmpi.<span class="me1">free</span> <span class="sy1"><<</span> <span class="st0">" "</span> <span class="sy1"><<</span> tmpi.<span class="me1">available</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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</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">. Capacity Free Available
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/dev: 4175114240 4175110144 4175110144
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/tmp: 420651237376 411962273792 390570749952</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-filesystem-space_info.html"><span class="t-lines"><span>space_info</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>关于文件系统上空闲及可用空间的信息<br />
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<span class="t-mark">(类)</span></td>
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</div>
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<div class="visualClear"></div>
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