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copy [C++ Reference]
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<span class="bchead">You are here: </span><a href="../start.html" title="start">C++ Reference</a> » <a href="../string/start.html" title="string:start">C++ Strings</a> » <a href="../string/copy.html" title="string:copy">copy</a> </div>
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<h2><a name="copy" id="copy">copy</a></h2>
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<p>
Syntax:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co2">#include <string></span>
size_type copy<span class="br0">(</span> Char<span class="sy0">*</span> str<span class="sy0">,</span> size_type num<span class="sy0">,</span> size_type index <span class="sy0">=</span> 0 <span class="br0">)</span> <span class="kw4">const</span><span class="sy0">;</span></pre>
<p>
The copy() function copies num characters of the current string (starting at
index if it's specified, 0 otherwise) into str.
The return value of copy() is the number of characters copied.
For example, the following code uses copy() to extract a substring of a string
into an array of characters:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="kw4">char</span> buf<span class="br0">[</span>30<span class="br0">]</span><span class="sy0">;</span>
memset<span class="br0">(</span> buf<span class="sy0">,</span> <span class="st0">'<span class="es5">\0</span>'</span><span class="sy0">,</span> 30 <span class="br0">)</span><span class="sy0">;</span>
<span class="kw4">string</span> str <span class="sy0">=</span> <span class="st0">"Trying is the first step towards success."</span><span class="sy0">;</span>
str.<span class="me1">copy</span><span class="br0">(</span> buf<span class="sy0">,</span> 24 <span class="br0">)</span><span class="sy0">;</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> buf <span class="sy0"><<</span> endl<span class="sy0">;</span></pre>
<p>
When run, this code displays:
</p>
<pre class="c code c++" style="font-family:monospace;"> Trying is the first step</pre>
<p>
Note that before calling copy(), we first call (Standard C String and
Character) memset() to fill the destination array with copies of the NULL
character. This step is included to make sure that the resulting array of
characters is NULL-terminated.
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Related Topics: <a href="../string/substr.html" class="wikilink1" title="string:substr">substr</a>
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