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/starts.txt <<'SED_INPUT_1'
START
middle
START
end
SED_INPUT_1

sed -n '1,/^START$/p' data/starts.txt