We just saw that common Unix utilities are often designed as filters, giving them the ability to read from their standard input and write to their standard output. This concept is elegantly extended to seamlessly combine together multiple utilities, using an IPC mechanism called a pipe.
Also, we recall that the Unix philosophy embraces the do one task only design. What if we have one program that does task A and another that does task B and we want to combine them? Ah, that's exactly what pipes do! Refer to the following code:
prg_does_taskA | prg_does_taskB
A pipe essentially is redirection performed twice: the output of the left-hand program becomes the input to the right-hand program. Of course, this implies that ...
