Getting gen_server/gen_fsm state for debugging

Question

Is it possible to obtain the current state of a gen_server process (presumably by sending some system message)? It could be useful when debugging.

Of cours

Answer 1

There is actually a function that returns the state directly: sys:get_state/1,2. It accepts pid or name of the process and can optionally be given a timeout.

Answer 2

Use sys:get_status/1,2 function. It's definition is:

get_status(Name,Timeout) -> 
    {status, Pid, {module, Mod}, [PDict, SysState, Parent, Dbg, Misc]}

SysState will contain state of the process. It works for all processes using OTP behaviors and other processes implementing proc_lib and sys requirements.