* On Monday 2005-11-07 at 21:40:49 +0100, Benno Schulenberg wrote: > So maybe the > following is a better text for 'info grep usage': > > 13. Why is this back-reference failing? > > echo "ba" | egrep '(a)\1|b\1' > > This gives no output, because the first alternate '(a)\1' does > not match, as there is no "aa" in the input, so the '\1' in the > second alternate has nothing to refer back to, meaning it will > never match anything. (The second alternate in this example > can only match if the first alternate has matched -- making > the second one superfluous.)
I like it.
