 class="code">open_out_gen mode perm filename</code> opens the named file for writing,
   as described above. The extra argument <code class="code">mode</code>
   specify the opening mode. The extra argument <code class="code">perm</code> specifies
   the file permissions, in case the file must be created.
   <a href="Pervasives.html#VALopen_out"><code class="code">open_out</code></a> and <a href="Pervasives.html#VALopen_out_bin"><code class="code">open_out_bin</code></a> are special
   cases of this functi