[lug] bash scripting question

[Chip Atkinson]

Greetings,

I'm trying to remember how to use the output of two commands without using
temp files.  Say for example that I wanted to grep two different files and
then diff the output of the greps.  
With temp files it would be

grep abc file1 > /tmp/f1
grep abc file2 > /tmp/f2
diff /tmp/f1 /tmp/f2

I know I've seen it done before but I don't know even the google terms.

Thanks in advance.
Chip