In Lab Three, we have implemented ls -1 | wc -1 by using dup() and pipe(). Based on that, write a program use two pipes to implement ls -1 | grep D | wc -l. In Lab Three, we have implemented ls -1 | wc -1 by using dup() and pipe(). Based on that, write a program use two pipes to implement ls -1 | grep D | wc -l