title: C string append
body: <p>I want to append two strings. I used the following command:</p>
  
  <pre><code>new_str = strcat(str1, str2);
  </code></pre>
  
  <p>This command changes the value of <code>str1</code>. I want <code>new_str</code> to be the concatanation of <code>str1</code> and <code>str2</code> and at the same time <code>str1</code> is not to be changed.</p>