title: Read a string line by line using c++
body: <p>I have a <code>std::string</code> with multiple lines and I need to read it line by line.
  Please show me how to do it with a small example.</p>
  
  <p>Ex: I have a string <code>string h;</code></p>
  
  <p>h will be:</p>
  
  <pre><code>Hello there.
  How are you today?
  I am fine, thank you.
  </code></pre>
  
  <p>I need to extract <code>Hello there.</code>, <code>How are you today?</code>, and <code>I am fine, thank you.</code> somehow.</p>