title: what is the meaning of ##family
body: <p>I am looking at the folloing socket api code in sockaddr.h where it has a define as</p>
  
  <pre><code>#define  __SOCKADDR_COMMON(sa_prefix) \   
  sa_family_t sa_prefix##family
  </code></pre>
  
  <p>How does this #define works ?</p>