Question

Command substitution requires the command to use ________

(a) standard input

(b) standard output

(c) standard error

(d) all of the mentioned

I got this question in an interview for internship.

This is a very interesting question from Command Substitution and Shell Variables in division The Shell of Unix

Answer 1

The correct answer is (b) standard output

The best I can explain: The shell enables one or more command arguments to be obtained from the standard output of another command. This feature is called command substitution and it requires the command to use the standard output (stream).