it does[0] you are redirecting stdout of both of the subprocesses (the things in brackets) to the stdin of the diff command (I think it creates two different in

it does[0] you are redirecting stdout of both of the subprocesses (the things in brackets) to the stdin of the diff command (I think it creates two different input streams, that diff knows how to compare). [0] http://tldp.org/LDP/abs/html/process-sub.html http://tldp.org/LDP/abs/html/process-sub.html