return nil, err
	}

	oldState := State{state{termios: *termios}}

	// This attempts to replicate the behaviour documented for cfmakeraw in
	// the termios(3) manpage.
	termios.Iflag &^= unix.IGNBRK | unix.BRKINT | unix.PARMRK | unix.ISTRIP | unix.INLCR | unix.IGNCR | unix.ICRNL | unix.IXON
	termios.Oflag &^= unix.OPOST
	termios.Lflag &^= unix.ECHO | unix.ECHONL | unix.ICANON | unix.ISIG | unix.IEXTEN

		$2 ~ /^I(SIG|CANON|CRNL|EXTEN|MAXBEL|STRIP|UTF8)$/ ||
		$2 ~ /^IGN/ ||
		$2 ~ /^IX(ON|ANY|OFF)$/ ||
		$2 ~ /^IN(LCR|PCK)$/ ||
		$2 ~ /(^FLU?SH)|(FLU?SH$)/ ||
		$2 ~ /^C(LOCAL|READ)$/ ||
		$2 == "BRKINT" ||
		$2 == "HUPCL" ||
		$2 == "PENDIN" ||
		$2 == "TOSTOP" ||
		$2 ~ /^PAR/ ||
		$2 ~ /^SIG[^_]/ ||
		$2 ~ /^O[CNPFP][A-Z]+[^_][A-Z]+$/ ||
		$2 ~ /^IN_/ ||
		$2 ~ /^LOCK_(SH|EX|NB|UN)$/ ||