168 lines
8.0 KiB
HTML
168 lines
8.0 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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<head><meta http-equiv="x-ua-compatible" content="ie=edge">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<title>atoi, atol, atoll</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_string_byte_atoi 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">atoi, atol, atoll</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-string.html">string</a>‎ | <a href="c-string-byte.html">byte</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><stdlib.h></code></div>
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<td></td>
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<td></td>
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<div><span class="mw-geshi c source-c"><span class="kw4">int</span> atoi<span class="br0">(</span> <span class="kw4">const</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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<div><span class="mw-geshi c source-c"><span class="kw4">long</span> atol<span class="br0">(</span> <span class="kw4">const</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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<div><span class="mw-geshi c source-c"><span class="kw4">long</span> <span class="kw4">long</span> atoll<span class="br0">(</span> <span class="kw4">const</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 class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-c99">(C99 起)</span></td>
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<td></td>
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<td></td>
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<td></td>
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<p>转译 <code>str</code> 所指的字节字符串中的整数值。</p>
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<p>舍弃任何空白符，直至找到首个非空白符，然后接收尽可能多的字符以组成合法的整数表示，并转换之为整数值。合法的整数值含下列部分：</p>
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<ul>
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<li><span class="t-mark">(可选)</span> 正或负号</li>
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<li>数位</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>str</td>
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<td>-</td>
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<td>指向要转译的空终止字符串的指针</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>成功时为对应 <code>str</code> 内容的整数值。若转换的值落在对应的返回类型范围外，则返回值未定义。若无法进行转换，则返回 <span class="t-c"><span class="mw-geshi c source-c">​<span class="nu0">0</span>​</span></span> 。</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="c source-c">
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<pre class="de1"><span class="co2">#include <stdio.h></span>
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<span class="co2">#include <stdlib.h></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
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<span class="br0">{</span>
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<a href="c-io-fprintf.html"><span class="kw848">printf</span></a><span class="br0">(</span><span class="st0">"%i<span class="es1">\n</span>"</span>, atoi<span class="br0">(</span><span class="st0">" -123junk"</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="c-io-fprintf.html"><span class="kw848">printf</span></a><span class="br0">(</span><span class="st0">"%i<span class="es1">\n</span>"</span>, atoi<span class="br0">(</span><span class="st0">"0"</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="c-io-fprintf.html"><span class="kw848">printf</span></a><span class="br0">(</span><span class="st0">"%i<span class="es1">\n</span>"</span>, atoi<span class="br0">(</span><span class="st0">"junk"</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 无可进行的转换</span>
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<a href="c-io-fprintf.html"><span class="kw848">printf</span></a><span class="br0">(</span><span class="st0">"%i<span class="es1">\n</span>"</span>, atoi<span class="br0">(</span><span class="st0">"2147483648"</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// UB ：在 int 范围外</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">-123
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0
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0
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-2147483648</pre></div>
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</div>
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</div>
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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>7.22.1.2 The atoi, atol, and atoll functions (p: 341)</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>7.20.1.2 The atoi, atol, and atoll functions (p: 307)</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>4.10.1.2 The atoi function</li>
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</ul>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li>4.10.1.3 The atol 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-string-byte-strtol.html"><span class="t-lines"><span>strtol</span><span>strtoll</span></span></a></div>
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<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div>
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</div>
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</td>
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<td>将字节字符串转换成整数值<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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<div class="t-dsc-member-div">
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<div><a href="c-string-byte-strtoul.html"><span class="t-lines"><span>strtoul</span> <span>strtoull</span></span></a></div>
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<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div>
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</div>
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</td>
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<td>将字节字符串转换成无符号整数值<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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