title: unistd : no such file or directory
body: <p>I have the following <code>test.cpp</code> file :</p>
  
  <pre><code>#include &lt;unistd&gt;
  
  int   main()
  {
      return 0;
  }
  </code></pre>
  
  <p>I just want to compile this but I still have the following :</p>
  
  <pre><code>$ g++ test.cpp
  test.cpp:1:18: fatal error: unistd: No such file or directory
   #include &lt;unistd&gt;
                    ^
  compilation terminated.
  </code></pre>
  
  <p>I found <code>unistd.h</code> at <code>/usr/include/unistd.h</code>. and my <code>$LD_LIBRARY_PATH</code> environment variable was empty so I set it at <code>/usr/include</code> (with <code>export LD_LIBRARY_PATH=/usr/include</code>) but the problem remains.
  What could I do?</p>