165 lines
10 KiB
HTML
165 lines
10 KiB
HTML
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<title>gets, gets_s</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_io_gets skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading">gets, gets_s</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="c.html">c</a>‎ | <a href="c-io.html">io</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><stdio.h></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-until-c11">
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<div><span class="mw-geshi c source-c"><span class="kw4">char</span> <span class="sy2">*</span>gets<span class="br0">(</span> <span class="kw4">char</span> <span class="sy2">*</span>str <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-until-c11">(C11 中移除)</span></td>
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<tr class="t-dcl t-since-c11">
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<div><span class="mw-geshi c source-c"><span class="kw4">char</span> <span class="sy2">*</span>gets_s<span class="br0">(</span> <span class="kw4">char</span> <span class="sy2">*</span>str, rsize_t n <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-c11">(C11 起)</span></td>
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<td></td>
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<div class="t-li1"><span class="t-li">1)</span> 从 <span class="t-lc"><a href="c-io.html">stdin</a></span> 读入 <code>str</code> 所指向的字符数组，直到发现换行符或出现文件尾。在读入数组的最后一个字符后立即写入空字符。换行符被舍弃，但不会存储于缓冲区中。</div>
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<div class="t-li1"><span class="t-li">2)</span> 从 <span class="t-lc"><a href="c-io.html">stdin</a></span> 读取字符直到发现换行符或出现文件尾。至多写入 <span class="t-c"><span class="mw-geshi c source-c">n<span class="sy2">-</span><span class="nu0">1</span></span></span> 个字符到 <code>str</code> 所指向的数组，并始终写入空终止字符（除非 <code>str</code> 是空指针）。若发现换行符，则忽略它并且不将它计入写入缓冲区的字符数。
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<dl>
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<dd>在运行时检测下列错误并调用当前安装的<a href="c-error-set_constraint_handler_s.html">制约处理</a>函数：
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<ul>
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<li><code>n</code> 为零</li>
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<li><code>n</code> 大于 <span class="t-c"><span class="mw-geshi c source-c">RSIZE_MAX</span></span></li>
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<li><code>str</code> 是空指针</li>
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<li>在存储 <span class="t-c"><span class="mw-geshi c source-c">n<span class="sy2">-</span><span class="nu0">1</span></span></span> 个字符到缓冲区后没有遇到换行符或文件尾。}}</li>
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</ul>
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</dd>
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<dd>任何情况下，<code>gets_s</code> 首先结束读取并忽略来自 <span class="t-lc"><a href="c-io.html">stdin</a></span> 的字符，直到换行符、文件尾条件，或在调用制约处理前的读取错误。</dd>
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<dd>同所有边界检查函数， <code>gets_s</code> 仅若实现定义 <span class="t-c"><span class="mw-geshi c source-c">__STDC_LIB_EXT1__</span></span> 且用户在包含 <code>stdio.h</code> 前定义 <span class="t-c"><span class="mw-geshi c source-c">__STDC_WANT_LIB_EXT1__</span></span> 为整数常量 1 才保证可用。</dd>
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</dl>
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</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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<table class="t-par-begin">
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<tr class="t-par">
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<td>str</td>
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<td>-</td>
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<td>要被写入的字符串</td>
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</tr>
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<tr class="t-par">
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<td>n</td>
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<td>-</td>
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<td>char数组的最大长度</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>成功时为 <code>str</code> ，失败时为空指针。</p>
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<p>若文件尾条件导致了失败，则附加设置 <span class="t-lc"><a href="c-io.html">stdin</a></span> 的<i>文件尾</i>指示器（见 <span class="t-lc"><a href="c-io-feof.html">feof()</a></span> ）。若其他某些原因导致了失败，则设置 <span class="t-lc"><a href="c-io.html">stdin</a></span> 的<i>错误</i>指示器（见 <span class="t-lc"><a href="c-io-ferror.html">ferror()</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><code>gets()</code> 函数不进行边界检查，从而此函数对缓冲区溢出攻击极度脆弱。无法安全使用它（除非程序运行的环境限定能出现在 <code>stdin</code> 上的内容）。因此，此函数在 C99 的第三次勘误中被弃用，而在 C11 标准发布时被移除。推荐的替代品是 <span class="t-lc"><a href="c-io-fgets.html">fgets()</a></span> 和 <code>gets_s()</code> 。</p>
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<p><b>绝对不要用 <code>gets()</code> 。</b></p>
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<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">引用</span></h3>
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<div class="t-ref-std-11">
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<ul>
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<li>C11 标准（ISO/IEC 9899:2011）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>K.3.5.4.1 The gets_s function (p: 602-603)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c99">
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<ul>
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<li>C99 标准（ISO/IEC 9899:1999）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>7.19.7.7 The gets function (p: 298)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c89">
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<ul>
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<li>C89/C90 标准（ISO/IEC 9899:1990）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>4.9.7.7 The gets function</li>
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</ul>
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</dd>
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</dl>
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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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<div class="t-dsc-member-div">
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<div><a href="c-io-fscanf.html"><span class="t-lines"><span>scanf</span><span>fscanf</span><span>sscanf</span><span>scanf_s</span><span>fscanf_s</span><span>sscanf_s</span></span></a></div>
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<div><span class="t-lines"><span></span><span></span><span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div>
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</div>
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</td>
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<td>从<span class="t-lc"><a href="c-io.html">stdin</a></span>、文件流或缓冲区读取格式化输入<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="c-io-fgets.html"><span class="t-lines"><span>fgets</span></span></a></div>
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</div>
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</td>
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<td>从文件流获取一个字符串<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="c-io-fputs.html"><span class="t-lines"><span>fputs</span></span></a></div>
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</div>
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</td>
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<td>将一个字符串写入文件流<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="c-experimental-dynamic-getline.html"><span class="t-lines"><span>getline</span><span>getwline</span><span>getdelim</span><span>getwdelim</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-dynamic-tr t-mark-ts">(动态内存 TR)</span></span></span></div>
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</div>
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</td>
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<td>从流读入至动态改变大小的缓冲区，直到分隔符/行尾<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>
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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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