+<p> This approach depends on file descriptor inheritance across
+<code>fork(2)</code>, so it does not work in the situation
+where neither process is an ancestor of the other. Files of
+type <em>fifo</em> (named pipes) overcome this restriction. To
+establish a connection between two <em>unrelated</em> processes,
+both processes call <code>open(2)</code> to obtain a file
+descriptor which is associated with the fifo. One process passes
+the <code>O_WRONLY</code> flag to open the file for writing while
+the other passes <code>O_RDONLY</code> to open it for reading. The
+two processes may then communicate in the same way as with the
+<code>pipe(2)/fork(2)</code> approach. </p>
+