250 lines
20 KiB
HTML
250 lines
20 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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<title>strtol, strtoll</title>
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<link rel="stylesheet" href="site_modules.css" />
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_string_byte_strtol 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">strtol, strtoll</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>
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<td></td>
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<td></td>
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</tr>
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</tbody>
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<tbody class="t-dcl-rev">
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<tr class="t-dcl t-until-c99">
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<td>
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<div><span class="mw-geshi c source-c"><span class="kw4">long</span> strtol<span class="br0">(</span> <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy2">*</span>str, <span class="kw4">char</span> <span class="sy2">**</span>str_end, <span class="kw4">int</span> base <span class="br0">)</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-until-c99">(C99 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-c99">
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<td>
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<div><span class="mw-geshi c source-c"><span class="kw4">long</span> strtol<span class="br0">(</span> <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy2">*</span><span class="kw4">restrict</span> str, <span class="kw4">char</span> <span class="sy2">**</span><span class="kw4">restrict</span> str_end, <span class="kw4">int</span> base <span class="br0">)</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-c99">(C99 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 t-since-c99">
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<td>
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<div><span class="mw-geshi c source-c"><span class="kw4">long</span> <span class="kw4">long</span> strtoll<span class="br0">(</span> <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy2">*</span><span class="kw4">restrict</span> str, <span class="kw4">char</span> <span class="sy2">**</span><span class="kw4">restrict</span> str_end, <span class="kw4">int</span> base <span class="br0">)</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-c99">(C99 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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</tr>
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</tbody>
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</table>
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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>舍弃所有空白符（以调用 <code>isspace()</code> 鉴别），直到找到首个非空白符，然后取尽可能多的字符组成<i>底 n</i> （其中 n=base ）的整数表示，并将它们转换成一个整数值。合法的整数值由下列部分组成：</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><span class="t-mark">(可选)</span>指示八进制底的前缀（ <code><b>0</b></code> ）（仅当底为 <span class="t-c"><span class="mw-geshi c source-c"><span class="nu0">8</span></span></span> 或 <span class="t-c"><span class="mw-geshi c source-c">​<span class="nu0">0</span>​</span></span> 时应用）</li>
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<li><span class="t-mark">(可选)</span>指示十六进制底的前缀（ <code><b>0x</b></code> 或 <code><b>0X</b></code> ）（仅当底为 <span class="t-c"><span class="mw-geshi c source-c"><span class="nu0">16</span></span></span> 或 <span class="t-c"><span class="mw-geshi c source-c">​<span class="nu0">0</span>​</span></span> 时应用）</li>
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<li>一个数字序列</li>
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</ul>
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<p>底的合法集是 {0,2,3,...,36} 。合法数字集对于底 2 整数是 <code>{0,1</code>}，对于底3整数是 <code>{0,1,2</code>} ，以此类推。对于大于 <code>10</code> 的底，合法数字包含字母字符，从对于底 11 整数的 <code>Aa</code> 到对于底36整数的 <code>Zz</code> 。忽略字符大小写。</p>
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<p>当前安装的 C <a href="c-locale-setlocale.html">本地环境</a>可能接受另外的数字格式。</p>
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<p>若 base 为 <span class="t-c"><span class="mw-geshi c source-c">​<span class="nu0">0</span>​</span></span> ，则自动检测数值进制：若前缀为 <code><b>0</b></code> ，则底为八进制，若前缀为 <code><b>0x</b></code> 或 <code><b>0X</b></code> ，则底为十六进制，否则底为十进制。</p>
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<p>若符号是输入序列的一部分，则对从数字序列计算得来的数字值取反，如同用结果类型的<a href="c-language-operator_arithmetic.html#.E4.B8.80.E5.85.83.E7.AE.97.E6.9C.AF">一元减</a>。</p>
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<p>函数设置 <code>str_end</code> 所指向的指针指向最后被转译字符的后一字符。若 <code>str_end</code> 为空指针，则忽略它。</p>
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<p>若 <code>str</code> 为空或无期待的形式，则不进行转换，并（若 <code>str_end</code> 不是空指针）将 <code>str</code> 的值存储于 <code>str_end</code> 所指的对象。</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>str</td>
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<td>-</td>
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<td>指向要被转译的空终止字符串的指针</td>
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</tr>
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<tr class="t-par">
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<td>str_end</td>
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<td>-</td>
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<td>指向指向字符指针的指针。</td>
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</tr>
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<tr class="t-par">
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<td>base</td>
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<td>-</td>
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<td>被转译整数值的<i>底</i></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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<ul>
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<li>若成功，则返回对应 <code>str</code> 内容的整数值。</li>
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<li>若被转换值落在对应返回类型的范围外，则发生值域错误（设 <span class="t-lc"><a href="c-error-errno.html">errno</a></span> 为 <span class="t-lc"><a href="c-error-errno_macros.html">ERANGE</a></span> ）并返回 <span class="t-lc"><a href="c-types-limits.html">LONG_MAX</a></span> 、 <span class="t-lc"><a href="c-types-limits.html">LONG_MIN</a></span> 、 <span class="t-lc"><a href="c-types-limits.html">LLONG_MAX</a></span> 或 <span class="t-lc"><a href="c-types-limits.html">LLONG_MIN</a></span> 。</li>
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<li>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> 。</li>
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</ul>
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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 <errno.h></span>
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<span class="co2">#include <limits.h></span>
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<span class="co2">#include <stdbool.h></span>
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<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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<span class="co1">// 带错误处理的剖析</span>
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<span class="kw4">const</span> <span class="kw4">char</span> <span class="sy2">*</span>p <span class="sy1">=</span> <span class="st0">"10 200000000000000000000000000000 30 -40 junk"</span><span class="sy4">;</span>
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<a href="c-io-fprintf.html"><span class="kw849">printf</span></a><span class="br0">(</span><span class="st0">"Parsing '%s':<span class="es1">\n</span>"</span>, p<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">for</span> <span class="br0">(</span><span class="sy4">;;</span><span class="br0">)</span>
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<span class="br0">{</span>
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<span class="co1">// 库函数调用能设置 errno 为任何非零值，无关乎是否有错误，</span>
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<span class="co1">// 故为检查 strtol 设置的错误，需要清除它</span>
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<span class="kw2">errno</span> <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span>
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<span class="kw4">char</span> <span class="sy2">*</span>end<span class="sy4">;</span>
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<span class="kw4">const</span> <span class="kw4">long</span> i <span class="sy1">=</span> strtol<span class="br0">(</span>p, <span class="sy3">&</span>end, <span class="nu0">10</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">if</span> <span class="br0">(</span>p <span class="sy1">==</span> end<span class="br0">)</span>
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<span class="kw1">break</span><span class="sy4">;</span>
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<span class="kw4">const</span> bool range_error <span class="sy1">=</span> <span class="kw2">errno</span> <span class="sy1">==</span> <a href="c-error-errno_macros.html"><span class="kw478">ERANGE</span></a><span class="sy4">;</span>
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<a href="c-io-fprintf.html"><span class="kw849">printf</span></a><span class="br0">(</span><span class="st0">"Extracted '%.*s', strtol returned %ld."</span>, <span class="br0">(</span><span class="kw4">int</span><span class="br0">)</span><span class="br0">(</span>end<span class="sy2">-</span>p<span class="br0">)</span>, p, i<span class="br0">)</span><span class="sy4">;</span>
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p <span class="sy1">=</span> end<span class="sy4">;</span>
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<span class="kw1">if</span> <span class="br0">(</span>range_error<span class="br0">)</span>
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<a href="c-io-fprintf.html"><span class="kw849">printf</span></a><span class="br0">(</span><span class="st0">" Range error occurred."</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="c-io-putchar.html"><span class="kw833">putchar</span></a><span class="br0">(</span><span class="st0">'<span class="es1">\n</span>'</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<a href="c-io-fprintf.html"><span class="kw849">printf</span></a><span class="br0">(</span><span class="st0">"Unextracted leftover: '%s'<span class="es1">\n</span><span class="es1">\n</span>"</span>, p<span class="br0">)</span><span class="sy4">;</span>
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<span class="co1">// 不带错误处理的剖析</span>
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<a href="c-io-fprintf.html"><span class="kw849">printf</span></a><span class="br0">(</span><span class="st0">"<span class="es1">\"</span>1010<span class="es1">\"</span> in binary --> %ld<span class="es1">\n</span>"</span>, strtol<span class="br0">(</span><span class="st0">"1010"</span>, <a href="c-types-NULL.html"><span class="kw103">NULL</span></a>, <span class="nu0">2</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="kw849">printf</span></a><span class="br0">(</span><span class="st0">"<span class="es1">\"</span>12<span class="es1">\"</span> in octal --> %ld<span class="es1">\n</span>"</span>, strtol<span class="br0">(</span><span class="st0">"12"</span>, <a href="c-types-NULL.html"><span class="kw103">NULL</span></a>, <span class="nu0">8</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="kw849">printf</span></a><span class="br0">(</span><span class="st0">"<span class="es1">\"</span>A<span class="es1">\"</span> in hex --> %ld<span class="es1">\n</span>"</span>, strtol<span class="br0">(</span><span class="st0">"A"</span>, <a href="c-types-NULL.html"><span class="kw103">NULL</span></a>, <span class="nu0">16</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="kw849">printf</span></a><span class="br0">(</span><span class="st0">"<span class="es1">\"</span>junk<span class="es1">\"</span> in base-36 --> %ld<span class="es1">\n</span>"</span>, strtol<span class="br0">(</span><span class="st0">"junk"</span>, <a href="c-types-NULL.html"><span class="kw103">NULL</span></a>, <span class="nu0">36</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="kw849">printf</span></a><span class="br0">(</span><span class="st0">"<span class="es1">\"</span>012<span class="es1">\"</span> in auto-detected base --> %ld<span class="es1">\n</span>"</span>, strtol<span class="br0">(</span><span class="st0">"012"</span>, <a href="c-types-NULL.html"><span class="kw103">NULL</span></a>, <span class="nu0">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="kw849">printf</span></a><span class="br0">(</span><span class="st0">"<span class="es1">\"</span>0xA<span class="es1">\"</span> in auto-detected base --> %ld<span class="es1">\n</span>"</span>, strtol<span class="br0">(</span><span class="st0">"0xA"</span>, <a href="c-types-NULL.html"><span class="kw103">NULL</span></a>, <span class="nu0">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="kw849">printf</span></a><span class="br0">(</span><span class="st0">"<span class="es1">\"</span>junk<span class="es1">\"</span> in auto-detected base --> %ld<span class="es1">\n</span>"</span>, strtol<span class="br0">(</span><span class="st0">"junk"</span>, <a href="c-types-NULL.html"><span class="kw103">NULL</span></a>, <span class="nu0">0</span><span class="br0">)</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">Parsing '10 200000000000000000000000000000 30 -40 junk':
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Extracted '10', strtol returned 10.
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Extracted ' 200000000000000000000000000000', strtol returned 9223372036854775807. Range error occurred.
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Extracted ' 30', strtol returned 30.
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Extracted ' -40', strtol returned -40.
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Unextracted leftover: ' junk'
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"1010" in binary --> 10
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"12" in octal --> 10
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"A" in hex --> 10
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"junk" in base-36 --> 926192
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"012" in auto-detected base --> 10
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"0xA" in auto-detected base --> 10
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"junk" in auto-detected base --> 0</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>7.22.1.4 The strtol, strtoll, strtoul, and strtoull functions (p: 344-345)</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>7.20.1.4 The strtol, strtoll, strtoul, and strtoull functions (p: 310-311)</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>4.10.1.5 The strtol 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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<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-string-byte-atoi.html"><span class="t-lines"><span>atoi</span><span>atol</span><span>atoll</span></span></a></div>
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<div><span class="t-lines"><span></span><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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<td>
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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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<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-string-wide-wcstol.html"><span class="t-lines"><span>wcstol</span><span>wcstoll</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-c95">(C95)</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>将宽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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<td>
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<div class="t-dsc-member-div">
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<div><a href="c-string-wide-wcstoul.html"><span class="t-lines"><span>wcstoul</span><span>wcstoull</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-c95">(C95)</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>将宽字符串转换成无符号整数值<br />
|
|
<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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