Elaborate on how a shell creates a pipe.

Author: janpgit

proc.tex

@@ -969,11 +969,15 @@
 need to check if \verb#pd[0] == 0#.
 \item It is better to create a pipe from a child to its parent as typically the
 process writing the pipe finishes first, then the consumer reads the rest of the
-data, processes it, and then finally exits.  Remember, the shell waits for the
+data, processes it, and then finally exits.  In general, the shell waits for the
 program it started, i.e. the parent, and it does not care at all about children
 the running program spawned during its life.  If the pipe was created the other
 way around, the shell could print the prompt after the parent finished while the
-data from the child might still be flowing to the console.
+data from the child might still be flowing to the console.  However, nowadays
+the shell waits for all processes in the pipeline.  For example, the following
+will take 10 seconds before you get the prompt even though \texttt{cat(1)} might
+exit right away if \texttt{sleep(1)} closed its standard error before putting
+itself to sleep: \texttt{date | sleep 10 | cat}.
 \item For example, the original \emph{Bourne shell} constructed a pipeline the
 way that the last process created a child as its producer, that producer itself
 created its child as its producer, and this continued until the whole pipeline