me=$0
say() { echo >&2 "($me) $1";      }
has() { which $1 >/dev/null 2>&1; return $?; }
check() {
	var=$1
	test "${!var}" == "" || return 0
	say "we were not able to detect a default value for the configuration variable \$$var. please set this variable to $2 and try again."
	exit 1
}