How to get PID afterwards if I forgot to assign the PID to a variable when I started the process

If in iex, i just did GenServer.start_link(MyModule, []) and forgot to assign the returned PID to a variable. How do I get that PID later in order to interact with that process?


From inside the process you can call self

If you’re in IEx, you can use the v command to get values from the history.

Typing v or v(-1) will get you the last value, v(-2) the value before that, and v(5) the value from line iex(5)>.


When calling start_link it returns a PID as you can see below;

iex> GenServer.start_link(MyModule, [])
{:ok, #PID<0.450.0>}

but when you’re not able to recover that into a variable there’s a way to transform the list/‘string’ format of that pid back into a real pid in the following way:

iex> pid = :erlang.list_to_pid('<0.450.0>')

iex> Process.alive? pid

So, now you have multiple ways to recover that PID ! :smile:


Or just pid(0, 450, 0)


is there a way to go into the process without the PID?

@benwilson512 @rjk @christopheradams all of your solutions are valid answers, thank you very much. Unfortunately I can only mark 1 answer as the solution.

In, the server parameter can be:

server :: pid | name | {atom, node}

pid - obviously won’t help you, but you can register the genserver by name globally:
You can e.g. use {:global, server_name_atom} where server_name_atom is the name you used when calling Genserver.start_link/3

with the last parameter (options) being [{:name, {:global, server_name_atom}}]

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