at first blush, my guess is that you escaped the question mark \? in what was supposed to be an ERE:
Originally Posted By: Virtual1
echo "nathan" | sed "s/na[t]\?han/_/g"

e.g., does this do what you want?

echo "nathan" |sed -E "s/na[t]?han/_/g"

Last edited by Hal Itosis; 09/30/11 06:20 PM.