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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head>  <meta name="generator" content=  "HTML Tidy for Linux/x86 (vers 1 September 2005), see www.w3.org">  <title>C++ String Streams</title>  <link href="../cppreference.css" rel="stylesheet" type="text/css"></head><body><table>  <tr>  <td>  <div class="body-content">  <div class="header-box">    <a href="../index.html">cppreference.com</a> &gt; <a href=    "index.html">C++ String Streams</a>  </div>  <div class="name-format">    String Stream Constructors  </div>  <div class="syntax-name-format">    Syntax:  </div>  <pre class="syntax-box">  #include &lt;sstream&gt;  stringstream()  stringstream( openmode mode )  stringstream( string s, openmode mode )  ostringstream()  ostringstream( openmode mode )  ostringstream( string s, openmode mode )  istringstream()  istringstream( openmode mode )  istringstream( string s, openmode mode )</pre>  <p>The stringstream, ostringstream, and istringstream objects are  used for input and output to a string.  They behave in a manner  similar to fstream, ofstream and ifstream objects.</p>  <p>The optional <em>mode</em> parameter defines how the file is to  be opened, according to the <a href="../io_flags.html#mode_flags">io  stream mode flags</a>.<p>  <p>An ostringstream object can be used to write to a string.  This  is similar to the C <a  href="../stdio/sprintf.html">sprintf()</a>  function.  For example:</p>  <pre class="example-code">  ostringstream s1;  int i = 22;  s1 &lt;&lt; "Hello " &lt;&lt; i &lt;&lt; endl;  string s2 = s1.str();  cout &lt;&lt; s2;</pre>  <p>An istringstream object can be used to read from a string.  This  is similar to the C <a  href="../stdio/sscanf.html">sscanf()</a>  function.  For example:</p>  <pre class="example-code">  istringstream stream1;  string string1 = "25";  stream1.str(string1);  int i;  stream1 &gt;&gt; i;  cout &lt;&lt; i &lt;&lt; endl;  // displays 25</pre>  <p>You can also specify the input string in the istringstream  constructor as in this example:</p>  <pre class="example-code">  string string1 = "25";  istringstream stream1(string1);  int i;  stream1 &gt;&gt; i;  cout &lt;&lt; i &lt;&lt; endl;  // displays 25</pre>  <p>A stringstream object can be used for both input and output to a  string like an fstream object.</p>  <div class="related-name-format">    Related topics:  </div>  <div class="related-content">    <a href="../cppio/index.html">C++ I/O Streams</a><br>  </div>  </div>  </td>    </tr>  </table></body></html><hr>  <div class="name-format">    String Stream Operators  </div>  <div class="syntax-name-format">    Syntax:  </div>  <pre class="syntax-box">  #include &lt;sstream&gt;  operator&lt;&lt;  operator&gt;&gt;</pre>  <p>Like <a href="../cppio/index.html">C++  I/O Streams</a>, the simplest way to use string streams is to take  advantage of the overloaded &lt;&lt; and &gt;&gt; operators.</p>  <p>The &lt;&lt; operator inserts data into the stream.  For  example:</p>  <pre class="example-code">  stream1 << "hello" << i;</pre>  <p>This example inserts the string "hello" and the variable <i>i</i>  into <i>stream1</i>.  In contrast, the &gt;&gt; operator extracts  data out of a string stream:</p>  <pre class="example-code">  stream1 >> i;</pre>  <p>This code reads a value from <i>stream1</i> and assigns the  variable <i>i</i> that value.</p>  <div class="related-name-format">    Related topics:  </div>  <div class="related-content">    <a href="../cppio/index.html">C++ I/O Streams</a><br>  </div>  </div>  </td>    </tr>  </table></body></html><hr>  <div class="name-format">    rdbuf  </div>  <div class="syntax-name-format">    Syntax:  </div>  <pre class="syntax-box">  #include &lt;sstream&gt;  stringbuf* rdbuf();</pre>  <p>The <em>rdbuf()</em> function returns a pointer to the string  buffer for the current string stream.</p>  <div class="related-name-format">    Related topics:  </div>  <div class="related-content">    <a href="str.html">str()</a><br>    <a href="../cppio/index.html">C++ I/O Streams</a><br>  </div>  </div>  </td>    </tr>  </table></body></html><hr>  <div class="name-format">    str  </div>  <div class="syntax-name-format">    Syntax:  </div>  <pre class="syntax-box">  #include &lt;sstream&gt;  void str( string s );  string str();</pre>  <p>The function <em>str()</em> can be used in two ways.  First, it can  be used to get a copy of the string that is being manipulated by the  current stream string.  This is most useful with output strings.  For example:</p>  <pre class="example-code">  ostringstream stream1;  stream1 &lt;&lt; "Testing!" &lt;&lt; endl;  cout &lt;&lt; stream1.str();</pre>  <p>Second, <em>str()</em> can be used to copy a string into the  stream.  This is most useful with input strings.  For example:</p>  <pre class="example-code">  istringstream stream1;  string string1 = "25";  stream1.str(string1);</pre>  <p><em>str()</em>, along with <em>clear()</em>, is also handy when  you need to clear the stream so that it can be reused:</p>  <pre class="example-code">  istringstream stream1;  float num;  // use it once  string string1 = "25 1 3.235\n1111111\n222222";  stream1.str(string1);  while( stream1 &gt;&gt; num ) cout &lt;&lt; "num: " &lt;&lt; num &lt;&lt; endl;  // displays numbers, one per line  // use the same string stream again with clear() and str()  string string2 = "1 2 3 4 5  6 7 8 9 10";  stream1.clear();  stream1.str(string2);  while( stream1 &gt;&gt; num ) cout &lt;&lt; "num: " &lt;&lt; num &lt;&lt; endl;  // displays numbers, one per line</pre>  <div class="related-name-format">    Related topics:  </div>  <div class="related-content">    <a href="rdbuf.html">rdbuf()</a><br>    <a href="../cppio/index.html">C++ I/O Streams</a><br>  </div>  </div>  </td>    </tr>  </table></body></html><hr></body></html>
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