run command and return the str format stdout

        Args:
            cmd: string
        Returns:
            str: what the command's echo

def readCmd(cls, cmd):
        """run command and return the str format stdout

        Args:
            cmd: string
        Returns:
            str: what the command's echo
        """
        args = shlex.split(cmd)
        proc = subprocess.Popen(args, stdout=subprocess.PIPE)
        (proc_stdout, proc_stderr) = proc.communicate(input=None)  # proc_stdin
        return proc_stdout.decode()