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<h1 id="firstHeading" class="firstHeading">strncat, strncat_s</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="c.html">c</a>&lrm; | <a href="c-string.html">string</a>&lrm; | <a href="c-string-byte.html">byte</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code>&lt;string.h&gt;</code></div>
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<td></td>
<td></td>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<td rowspan="142">(1)</td>
<td></td>
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<tr class="t-dcl t-until-c99">
<td>
<div><span class="mw-geshi c source-c"><span class="kw4">char</span> <span class="sy2">*</span>strncat<span class="br0">(</span> <span class="kw4">char</span> <span class="sy2">*</span>dest, <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy2">*</span>src, <a href="c-types-size_t.html"><span class="kw100">size_t</span></a> count <span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-until-c99">(C99 &#21069;)</span></td>
</tr>
<tr class="t-dcl t-since-c99">
<td>
<div><span class="mw-geshi c source-c"><span class="kw4">char</span> <span class="sy2">*</span>strncat<span class="br0">(</span> <span class="kw4">char</span> <span class="sy2">*</span><span class="kw4">restrict</span> dest, <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy2">*</span><span class="kw4">restrict</span> src, <a href="c-types-size_t.html"><span class="kw100">size_t</span></a> count <span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-c99">(C99 &#36215;)</span></td>
</tr>
</tbody>
<tbody>
<tr class="t-dcl t-since-c11">
<td>
<div><span class="mw-geshi c source-c">errno_t strncat_s<span class="br0">(</span><span class="kw4">char</span> <span class="sy2">*</span><span class="kw4">restrict</span> dest, rsize_t destsz,<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy2">*</span><span class="kw4">restrict</span> src, rsize_t count<span class="br0">)</span><span class="sy4">;</span></span></div>
</td>
<td>(2)</td>
<td><span class="t-mark-rev t-since-c11">(C11 &#36215;)</span></td>
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<div class="t-li1"><span class="t-li">1)</span> &#21518;&#38468;&#26469;&#33258; <code>src</code> &#25152;&#25351;&#21521;&#30340;&#23383;&#31526;&#25968;&#32452;&#30340;&#33267;&#22810; <code>count</code> &#20010;&#23383;&#31526;&#65292;&#21040; <code>dest</code> &#25152;&#25351;&#21521;&#30340;&#31354;&#32456;&#27490;&#23383;&#33410;&#23383;&#31526;&#20018;&#30340;&#26411;&#23614;&#65292;&#33509;&#25214;&#21040;&#31354;&#23383;&#31526;&#21017;&#20572;&#27490;&#12290;&#23383;&#31526; <span class="t-c"><span class="mw-geshi c source-c">src<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span></span></span> &#26367;&#25442;&#20301;&#20110; <code>dest</code> &#26411;&#23614;&#30340;&#31354;&#32456;&#27490;&#31526;&#12290;&#22987;&#32456;&#21518;&#38468;&#32456;&#27490;&#31354;&#23383;&#31526;&#21040;&#26411;&#23614;&#65288;&#25925;&#20989;&#25968;&#21487;&#20889;&#20837;&#30340;&#26368;&#22823;&#23383;&#33410;&#25968;&#26159; <span class="t-c"><span class="mw-geshi c source-c">count<span class="sy2">+</span><span class="nu0">1</span></span></span> &#65289;&#12290;</div>
<div class="t-li1"><span class="t-li"></span> &#33509;&#30446;&#26631;&#25968;&#32452;&#27809;&#26377;&#23545;&#20110; <code>dest</code> &#21644; <code>src</code> &#30340;&#39318; <code>count</code> &#20010;&#23383;&#31526;&#21152;&#19978;&#32456;&#27490;&#31354;&#23383;&#31526;&#30340;&#36275;&#22815;&#31354;&#38388;&#65292;&#21017;&#34892;&#20026;&#26410;&#23450;&#20041;&#12290;&#33509;&#28304;&#19982;&#30446;&#26631;&#23545;&#35937;&#37325;&#21472;&#65292;&#21017;&#34892;&#20026;&#26410;&#23450;&#20041;&#12290;&#33509; <code>dest</code> &#19981;&#26159;&#25351;&#21521;&#31354;&#32456;&#27490;&#23383;&#33410;&#23383;&#31526;&#20018;&#30340;&#25351;&#38024;&#65292;&#25110; <code>src</code> &#19981;&#26159;&#25351;&#21521;&#23383;&#31526;&#25968;&#32452;&#30340;&#25351;&#38024;&#65292;&#21017;&#34892;&#20026;&#26410;&#23450;&#20041;&#12290;</div>
<div class="t-li1"><span class="t-li">2)</span> &#21516; <span class="t-v">(1)</span> &#65292;&#38500;&#20102;&#20989;&#25968;&#21487;&#20197;&#21487;&#29992;&#26410;&#25351;&#23450;&#20540;&#30772;&#22351;&#30446;&#26631;&#25968;&#32452;&#30340;&#21097;&#20313;&#37096;&#20998;&#65288;&#20174;&#26368;&#21518;&#20889;&#20837;&#23383;&#31526;&#21040; <code>destsz</code> &#65289;&#65292;&#20197;&#21450;&#22312;&#36816;&#34892;&#26102;&#26816;&#27979;&#19979;&#21015;&#38169;&#35823;&#65292;&#24182;&#35843;&#29992;&#24403;&#21069;&#23433;&#35013;&#30340;<a href="c-error-set_constraint_handler_s.html">&#21046;&#32422;&#22788;&#29702;</a>&#20989;&#25968;&#65306;
<dl>
<dd>
<ul>
<li><code>src</code> &#25110; <code>dest</code> &#20026;&#31354;&#25351;&#38024;</li>
<li><code>destsz</code> &#25110; <code>count</code> &#20026;&#38646;&#25110;&#22823;&#20110; <span class="t-lc">RSIZE_MAX</span></li>
<li><code>dest</code> &#30340;&#39318; <code>destsz</code> &#20010;&#23383;&#33410;&#20013;&#26080;&#31354;&#23383;&#31526;</li>
<li>&#20250;&#20986;&#29616;&#25130;&#26029;&#65306; <code>count</code> &#19982; <code>src</code> &#38271;&#24230;&#30340;&#36739;&#23567;&#32773;&#65292;&#20250;&#36229;&#20986; <code>dest</code> &#30340;&#31354;&#32456;&#27490;&#31526;&#21644; <code>destsz</code> &#20043;&#38388;&#30340;&#21487;&#29992;&#31354;&#38388;&#12290;</li>
<li>&#28304;&#19982;&#30446;&#26631;&#23383;&#31526;&#20018;&#20043;&#38388;&#20250;&#20986;&#29616;&#37325;&#21472;</li>
</ul>
</dd>
</dl>
</div>
<div class="t-li1"><span class="t-li"></span> &#33509; <code>dest</code> &#25152;&#25351;&#21521;&#30340;&#23383;&#31526;&#25968;&#32452;&#22823;&#23567; &lt; <span class="t-c"><span class="mw-geshi c source-c">strnlen<span class="br0">(</span>dest,destsz<span class="br0">)</span><span class="sy2">+</span>strnlen<span class="br0">(</span>src,count<span class="br0">)</span><span class="sy2">+</span><span class="nu0">1</span></span></span> &lt; <code>destsz</code> &#21017;&#34892;&#20026;&#26410;&#23450;&#20041;&#65307;&#25442;&#35328;&#20043;&#65292; <code>destsz</code> &#30340;&#38169;&#35823;&#20540;&#19981;&#26292;&#38706;&#34892;&#23558;&#21457;&#29983;&#30340;&#32531;&#20914;&#21306;&#28322;&#20986;&#12290;&#33509; <code>src</code> &#25152;&#25351;&#21521;&#30340;&#23383;&#31526;&#25968;&#32452;&#22823;&#23567; &lt; <span class="t-c"><span class="mw-geshi c source-c">strnlen<span class="br0">(</span>src,count<span class="br0">)</span></span></span> &lt; <code>destsz</code> &#65307;&#25442;&#35328;&#20043;&#65292; <code>count</code> &#30340;&#38169;&#35823;&#20540;&#19981;&#26292;&#38706;&#34892;&#23558;&#21457;&#29983;&#30340;&#32531;&#20914;&#21306;&#28322;&#20986;&#12290;
<dl>
<dd></dd>
<dd>&#21516;&#25152;&#26377;&#36793;&#30028;&#26816;&#26597;&#20989;&#25968;&#65292; <code>strncat_s</code> &#20165;&#33509;&#23454;&#29616;&#23450;&#20041;&#20102; <span class="t-c"><span class="mw-geshi c source-c">__STDC_LIB_EXT1__</span></span> &#65292;&#19988;&#29992;&#25143;&#22312;&#21253;&#21547; <code>string.h</code> &#21069;&#23450;&#20041; <span class="t-c"><span class="mw-geshi c source-c">__STDC_WANT_LIB_EXT1__</span></span> &#20026;&#25972;&#25968;&#24120;&#37327; <span class="t-c"><span class="mw-geshi c source-c"><span class="nu0">1</span></span></span> &#25165;&#20445;&#35777;&#21487;&#29992;&#12290;</dd>
</dl>
</div>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
<table class="t-par-begin">
<tr class="t-par">
<td>dest</td>
<td>-</td>
<td>&#25351;&#21521;&#35201;&#21518;&#38468;&#21040;&#30340;&#31354;&#32456;&#27490;&#23383;&#33410;&#23383;&#31526;&#20018;&#30340;&#25351;&#38024;</td>
</tr>
<tr class="t-par">
<td>src</td>
<td>-</td>
<td>&#25351;&#21521;&#20316;&#20026;&#22797;&#21046;&#26469;&#28304;&#30340;&#23383;&#31526;&#25968;&#32452;&#30340;&#25351;&#38024;</td>
</tr>
<tr class="t-par">
<td>count</td>
<td>-</td>
<td>&#35201;&#22797;&#21046;&#30340;&#26368;&#22823;&#23383;&#31526;&#25968;</td>
</tr>
<tr class="t-par">
<td>destsz</td>
<td>-</td>
<td>&#30446;&#26631;&#32531;&#20914;&#21306;&#30340;&#22823;&#23567;</td>
</tr>
</table>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<div class="t-li1"><span class="t-li">1)</span> &#36820;&#22238; <code>dest</code> &#30340;&#21103;&#26412;&#12290;</div>
<div class="t-li1"><span class="t-li">2)</span> &#25104;&#21151;&#26102;&#36820;&#22238;&#38646;&#12290;&#38169;&#35823;&#26102;&#36820;&#22238;&#38750;&#38646;&#12290;&#38169;&#35823;&#26102;&#65292;&#20134;&#20889;&#20837;&#38646;&#21040; <span class="t-c"><span class="mw-geshi c source-c">dest<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span></span></span> &#65288;&#38500;&#38750; <code>dest</code> &#20026;&#31354;&#25351;&#38024;&#65292;&#25110; <code>destsz</code> &#20026;&#38646;&#25110;&#22823;&#20110; <span class="t-lc">RSIZE_MAX</span> &#65289;&#12290;</div>
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">&#27880;&#35299;</span></h3>
<p>&#22240;&#20026; <code>strncat</code> &#38656;&#35201;&#22312;&#27599;&#27425;&#35843;&#29992;&#26102;&#25214;&#21040; <code>dest</code> &#30340;&#32467;&#23614;&#65292;&#25925;&#29992; <code>strncat</code> &#23558;&#22810;&#20010;&#23383;&#31526;&#20018;&#36830;&#25509;&#25104;&#19968;&#20307;&#26159;&#20302;&#25928;&#30340;&#12290;</p>
<p>&#23613;&#31649;&#25130;&#26029;&#20197;&#36866;&#24212;&#30446;&#26631;&#32531;&#20914;&#21306;&#26159;&#23433;&#20840;&#39118;&#38505;&#65292;&#20174;&#32780;&#26159; <code>strncat_s</code> &#30340;&#36816;&#34892;&#26102;&#21046;&#32422;&#36829;&#35268;&#65292;&#36824;&#26159;&#21487;&#20197;&#36890;&#36807;&#25351;&#23450; <code>count</code> &#31561;&#20110;&#30446;&#26631;&#25968;&#32452;&#22823;&#23567;&#20943;&#19968;&#33719;&#21462;&#25130;&#26029;&#34892;&#20026;&#65306;&#36825;&#23558;&#19968;&#22914;&#24448;&#24120;&#22320;&#22797;&#21046;&#39318; <code>count</code> &#20010;&#23383;&#33410;&#24182;&#21518;&#38468;&#31354;&#32456;&#27490;&#31526;&#65306; <span class="t-c"><span class="mw-geshi c source-c">strncat_s<span class="br0">(</span>dst, <span class="kw4">sizeof</span> dst, src, <span class="br0">(</span><span class="kw4">sizeof</span> dst<span class="br0">)</span><span class="sy2">-</span>strnlen_s<span class="br0">(</span>dst, <span class="kw4">sizeof</span> dst<span class="br0">)</span><span class="sy2">-</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span></span></span> &#12290;</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
<div class="t-example">
<div class="t-example-live-link"></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="c source-c">
<pre class="de1"><span class="co2">#define __STDC_WANT_LIB_EXT1__ 1</span>
<span class="co2">#include &lt;string.h&gt; </span>
<span class="co2">#include &lt;stdio.h&gt;</span>
<span class="co2">#include &lt;stdlib.h&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
<span class="br0">{</span>
<span class="kw4">char</span> str<span class="br0">[</span><span class="nu0">50</span><span class="br0">]</span> <span class="sy1">=</span> <span class="st0">&quot;Hello &quot;</span><span class="sy4">;</span>
<span class="kw4">char</span> str2<span class="br0">[</span><span class="nu0">50</span><span class="br0">]</span> <span class="sy1">=</span> <span class="st0">&quot;World!&quot;</span><span class="sy4">;</span>
<a href="c-string-byte-strcat.html"><span class="kw555">strcat</span></a><span class="br0">(</span>str, str2<span class="br0">)</span><span class="sy4">;</span>
strncat<span class="br0">(</span>str, <span class="st0">&quot; Goodbye World!&quot;</span>, <span class="nu0">3</span><span class="br0">)</span><span class="sy4">;</span>
<a href="c-io-puts.html"><span class="kw835">puts</span></a><span class="br0">(</span>str<span class="br0">)</span><span class="sy4">;</span>
<span class="co2">#ifdef __STDC_LIB_EXT1__</span>
set_constraint_handler_s<span class="br0">(</span>ignore_handler_s<span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">char</span> s1<span class="br0">[</span><span class="nu0">100</span><span class="br0">]</span> <span class="sy1">=</span> <span class="st0">&quot;good&quot;</span><span class="sy4">;</span>
<span class="kw4">char</span> s5<span class="br0">[</span><span class="nu0">1000</span><span class="br0">]</span> <span class="sy1">=</span> <span class="st0">&quot;bye&quot;</span><span class="sy4">;</span>
<span class="kw4">int</span> r1 <span class="sy1">=</span> strncat_s<span class="br0">(</span>s1, <span class="nu0">100</span>, s5, <span class="nu0">1000</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// r1 &#20026; 0 &#65292; s1 &#20445;&#26377; &quot;goodbye\0&quot;</span>
<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">&quot;s1 = %s, r1 = %d<span class="es1">\n</span>&quot;</span>, s1, r1<span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">char</span> s2<span class="br0">[</span><span class="nu0">6</span><span class="br0">]</span> <span class="sy1">=</span> <span class="st0">&quot;hello&quot;</span><span class="sy4">;</span>
<span class="kw4">int</span> r2 <span class="sy1">=</span> strncat_s<span class="br0">(</span>s2, <span class="nu0">6</span>, <span class="st0">&quot;&quot;</span>, <span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// r2 &#20026; 0 &#65292; s2 &#20445;&#26377; &quot;hello\0&quot;</span>
<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">&quot;s2 = %s, r2 = %d<span class="es1">\n</span>&quot;</span>, s2, r2<span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">char</span> s3<span class="br0">[</span><span class="nu0">6</span><span class="br0">]</span> <span class="sy1">=</span> <span class="st0">&quot;hello&quot;</span><span class="sy4">;</span>
<span class="kw4">int</span> r3 <span class="sy1">=</span> strncat_s<span class="br0">(</span>s3, <span class="nu0">6</span>, <span class="st0">&quot;X&quot;</span>, <span class="nu0">2</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// r3 &#38750;&#38646;&#65292; s3 &#20445;&#26377; &quot;\0&quot;</span>
<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">&quot;s3 = %s, r3 = %d<span class="es1">\n</span>&quot;</span>, s3, r3<span class="br0">)</span><span class="sy4">;</span>
<span class="co1">// the strncat_s truncation idiom:</span>
<span class="kw4">char</span> s4<span class="br0">[</span><span class="nu0">7</span><span class="br0">]</span> <span class="sy1">=</span> <span class="st0">&quot;abc&quot;</span><span class="sy4">;</span>
<span class="kw4">int</span> r4 <span class="sy1">=</span> strncat_s<span class="br0">(</span>s4, <span class="nu0">7</span>, <span class="st0">&quot;defghijklmn&quot;</span>, <span class="nu0">3</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// r &#20026; 0 &#65292; s4 &#20445;&#26377; &quot;abcdef\0&quot;</span>
<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">&quot;s4 = %s, r4 = %d<span class="es1">\n</span>&quot;</span>, s4, r4<span class="br0">)</span><span class="sy4">;</span>
<span class="co2">#endif</span>
<span class="br0">}</span></pre></div>
</div>
<p>&#21487;&#33021;&#30340;&#36755;&#20986;&#65306;</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="text source-text">
<pre class="de1">Hello World! Go
s1 = goodbye, r1 = 0
s2 = hello, r2 = 0
s3 = , r3 = 22
s4 = abcdef, r4 = 0</pre></div>
</div>
</div>
<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">&#24341;&#29992;</span></h3>
<div class="t-ref-std-11">
<ul>
<li>C11 &#26631;&#20934;&#65288;ISO/IEC 9899:2011&#65289;&#65306;</li>
</ul>
<dl>
<dd>
<ul>
<li>7.24.3.2 The strncat function (p: 364-365)</li>
</ul>
</dd>
</dl>
<dl>
<dd>
<ul>
<li>K.3.7.2.2 The strncat_s function (p: 618-620)</li>
</ul>
</dd>
</dl>
<div class="t-ref-std-c99">
<ul>
<li>C99 &#26631;&#20934;&#65288;ISO/IEC 9899:1999&#65289;&#65306;</li>
</ul>
<dl>
<dd>
<ul>
<li>7.21.3.2 The strncat function (p: 327-328)</li>
</ul>
</dd>
</dl>
<div class="t-ref-std-c89">
<ul>
<li>C89/C90 &#26631;&#20934;&#65288;ISO/IEC 9899:1990&#65289;&#65306;</li>
</ul>
<dl>
<dd>
<ul>
<li>4.11.3.2 The strncat function</li>
</ul>
</dd>
</dl>
</div>
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
<table class="t-dsc-begin">
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="c-string-byte-strcat.html"><span class="t-lines"><span>strcat</span><span>strcat_s</span></span></a></div>
<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div>
</div>
</td>
<td>&#36830;&#25509;&#20004;&#20010;&#23383;&#31526;&#20018;<br />
<span class="t-mark">(&#20989;&#25968;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="c-string-byte-strcpy.html"><span class="t-lines"><span>strcpy</span><span>strcpy_s</span></span></a></div>
<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div>
</div>
</td>
<td>&#22797;&#21046;&#19968;&#20010;&#23383;&#31526;&#20018;&#32473;&#21478;&#19968;&#20010;<br />
<span class="t-mark">(&#20989;&#25968;)</span></td>
</tr>
</table>
</div>
</div>
</div>
<div class="visualClear"></div>
</div>
</div>
</div>
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