What happens to a canister if i don't have enough tokens to pay?

[d2k]

you asked two questions and you might want to seperate them - on the second one check

Getting a user's identity

V0.5.0 added principalId to the standard library allowing you to work with a shared function’s {caller} object, here’s an example retrieving an external caller’s id: import PrincipalId "mo:stdlib/principalId"; import Hash "mo:stdlib/hash"; import Prim "mo:prim"; type Id = Hash.Hash; actor { func getUserId(user: Principal) : Id { return PrincipalId.hash(user); }; public shared x func main() { Prim.debugPrint(debug_show( getUserId(x.caller) )); }; };

and there are some other posts addressing this. So you can control access to the canisters.

On the what happens if you run out of token in a canister - this is a quite interesting one where I have no answer for…