set -euo pipefail
export LC_ALL=C
sed_work=$(mktemp -d "${TMPDIR:-/tmp}/sed-example.XXXXXX")
trap 'rm -rf -- "$sed_work"' EXIT
cd "$sed_work"
mkdir -p data
cat > data/names.txt <<'SED_INPUT_1'
alice:17
bob:204
SED_INPUT_1

sed -En 's/^([a-z]+):([0-9]+)$/\1=\2; owner=\1/p' data/names.txt