code: def _get_systemd_services(root):
      '''
      Use os.listdir() to get all the unit files
      '''
      ret = set()
      for path in SYSTEM_CONFIG_PATHS + (LOCAL_CONFIG_PATH,):
          # Make sure user has access to the path, and if the path is a
          # link it's likely that another entry in SYSTEM_CONFIG_PATHS
          # or LOCAL_CONFIG_PATH points to it, so we can ignore it.
          path = _root(path, root)
          if os.access(path, os.R_OK) and not os.path.islink(path):
              for fullname in os.listdir(path):
                  try:
                      unit_name, unit_type = fullname.rsplit('.', 1)
                  except ValueError:
                      continue
                  if unit_type in VALID_UNIT_TYPES:
                      ret.add(unit_name if unit_type == 'service' else fullname)
      return ref _get_systemd_services(root):
      '''
      Use os.listdir() to get all the unit files
      '''
      ret = set()
      for path in SYSTEM_CONFIG_PATHS + (LOCAL_CONFIG_PATH,):
          # Make sure user has access to the path, and if the path is a
          # link it's likely that another entry in SYSTEM_CONFIG_PATHS
          # or LOCAL_CONFIG_PATH points to it, so we can ignore it.
          path = _root(path, root)
          if os.access(path, os.R_OK) and not os.path.islink(path):
              for fullname in os.listdir(path):
                  try:
                      unit_name, unit_type = fullname.rsplit('.', 1)
                  except ValueError:
                      continue
                  if unit_type in VALID_UNIT_TYPES:
                      ret.add(unit_name if unit_type == 'service' else fullname)
      return ret
docs: Use os.listdir() to get all the unit files