fmt.Fprintf(&exitReStr, "%s([0-9]+)$", exitStr)
	exitRe := regexp.MustCompile(exitReStr.String())

	return &exitCodeFilter{w: w, exitRe: exitRe}, exitStr
}

func (f *exitCodeFilter) Write(data []byte) (int, error) {
	n := len(data)
	f.buf.Write(data)
	// Flush to w until a potential match of exitRe
	b := f.buf.Bytes()
	match := f.exitRe.FindIndex(b)
	if match == nil {
		// Flush all of the buffer.