Eh can mean many different things, depending on the context and the speaker... It can mean :
Eh = what did you say?
Eh? = what do you think
Eh!! = WOW!!
EH? = what do you mean?
Eh?? = your joking!!!??
EH!! = Hello..you off in the distance!!!
Eh..cmon eh? = asking them to let you pay for it next time.
Eh...uhuh = yes sure!
but in a sentance its meaning depends on the situation...
Speaker 1: Did you see that guy over there?
Speaker 2: eh?
Speaker 1: The guy with the red hat.
Speaker 2: Ya... what about him?
Speaker 1: He pushed that old lady in line.
Speaker 2: How rude eh.
Speaker 1: ya.