Diff output from two programs without temporary files

Question

Say I have too programs a and b that I can run with ./a and ./b.

Is it possible to diff their outputs without first w

Answer 1

One option would be to use named pipes (FIFOs):

mkfifo a_fifo b_fifo
./a > a_fifo &
./b > b_fifo &
diff a_fifo b_fifo

... but John Kugelman's solution is much cleaner.