code: def exec_output(cls, command, shell=True, encoding='utf-8'):
          
          proc = Popen(command, shell=shell, stdout=PIPE)
          stdout, _stderr = proc.communicate()
          if proc.returncode == 0:
              return stdout.decode(encoding)
  
          return ''
docs: Return execution output
  
          :param encoding: charset used to decode the stdout
          :type encoding: str
  
          :return: the return of the command
          :rtype: unicode string