Question

In a pipeline, the command on the left of | must use standard output and one on the right must use standard input.

(a) True

(b) False

This question was addressed to me by my college director while I was bunking the class.

Asked question is from Redirection and Pipes in division The Shell of Unix

Answer 1

Right answer is (a) True

To elaborate: There is a restriction which is applied while using a pipeline. In a pipeline, the command on the left of | must use standard output (stream)  and one on the right must use standard input (stream). Otherwise, an error will be generated or the output will be erroneous.