// The signal name should start with "SIG".
func SignalNum(s string) syscall.Signal {
	signalNameMapOnce.Do(func() {
		signalNameMap = make(map[string]syscall.Signal, len(signalList))
		for _, signal := range signalList {
			signalNameMap[signal.name] = signal.num
		}
	})
	return signalNameMap[s]
}

// clen returns the index of the first NULL byte in n or len(n) if n contains no NULL byte.
func clen(n []byte) int {