foo.erl

# (arity 0)
root@deleteme:~/foo# bin/foo rpc Foo bar
RPC to 'foo@127.0.0.1' failed: {'EXIT',
                                {undef,
                                 [{'Foo',bar,[],[]},
                                  {rpc,'-handle_call_call/6-fun-0-',5,
                                   [{file,"rpc.erl"},{line,205}]}]}}
                                   
root@deleteme:~/foo# bin/foo rpc Elixir.Foo bar                                   
yeah!
:ok

# (arity 1) -- note the erlang terms and '.' at the end... we have to pass an array of the args, which in our case is an array
What about with arguments to Elixir.Foo main? 

root@deleteme:~/foo# bin/foo rpc Elixir.Foo main "[1]"
escript: exception error: no match of right hand side value
                 {error,{0,erl_parse,["syntax error before: ",[]]}}
                 

root@deleteme:~/foo# bin/foo rpc Elixir.Foo main "[[1,2,3]]."
Your arg is 1
Your arg is 2
Your arg is 3
[ok,ok,ok]

# Finally, the escript way that doesn't require bin/foo start

root@deleteme:~/foo# bin/foo escript lib/foo-0.0.1/ebin/Elixir.Foo.beam "fo" "bar" 1 2 3
Your arg is fo
Your arg is bar
Your arg is 1
Your arg is 2
Your arg is 3