如何进行双管通气

$ candump can0

$ candump can0 | grep <whatever>

  $ candump can0 | grep 1A8           
  can0  1A8   [8]  3C 53 C5 FF 0D C3 3A 01
  can0  1A8   [8]  3C 53 C5 FF 0D C3 3A 01

如果我尝试grep它两次:

candump can0 | grep 1A8 | grep 1A8

它什么也不返回。。。

Ps:可以用这个解决( candump can0,<whatever>,7ff | grep <whatever>

编辑:为了清楚起见,如果我重复两次同样的事情,它仍然不起作用