@vehomzzz's answer uses find and xargs when the questions says explicitly grep and sed only.
@EmployedRussian and @BrooksMoses tried to say it was a dup of awk and sed, but it's not - again, the question explicitly says grep and sedonly.
So here is my solution, assuming you are using Bash as your shell:
OLDIFS=$IFS
IFS=$'\n'
for f in `grep -rl a.example.com .` # Use -irl instead of -rl for case insensitive search
do
sed -i 's/a\.example\.com/b.example.com/g' $f # Use /gi instead of /g for case insensitive search
done
IFS=$OLDIFS
If you are using a different shell, such as Unix SHell, let me know and I will try to find a syntax adjustment.
P.S.: Here's a one-liner:
OLDIFS=$IFS;IFS=$'\n';for f in `grep -rl a.example.com .`;do sed -i 's/a\.example\.com/b.example.com/g' $f;done;IFS=$OLDIFS