#!/bin/sh
set -eu

usage() {
	cat <<-'EOF'
		Usage:
		  pre PREFIX < STDIN
	EOF
}


PREFIX="${1:-}"
eval "$(assert-arg -- "$PREFIX" 'PREFIX')"

# FIXME: using "while" so we avoid GNU sed's buffering
while read -r line; do
	printf '%s: %s\n' "$PREFIX" "$line"
done