title: strcat paste second string at beginning of first string
body: <p>i use <code>strcat()</code> to connect two strings like:  </p>
  
  <pre><code>    #include &lt;string.h&gt;
      #include &lt;stdio.h&gt;
  
      int main(int argc, char *args[])
      {
         char *str1; // "456"
         char *str2; // "123"
  
         strcat(str1,str2);
         printf("%s",str1);
      }
  </code></pre>
  
  <p>i get:  </p>
  
  <pre><code>456123  
  </code></pre>
  
  <p>but i need the second string on beginning of first string like: </p>
  
  <pre><code>123456
  </code></pre>
  
  <p>how can i do it ?</p>