repeat the last single shell command

[Luca Ferrari]

Hi,
this should be trivial, but I'm not able to find an easy and simple
way of running again the last single shell command (M-!). I know I can
use the shell ring to get back the last command, like M-P so that I
have to:

M-! M-p RET

but I guess there is a smarter way. And I don't want to open a full
shell, this is supposed to let me test quickly a shell script.

Thanks,
Luca