Demo for process_flag

demo.erl

-module(demo). 
-compile(export_all). 

start(Bool, M) ->
	A = spawn(fun()->a()end),
	B = spawn(fun()->b(A,Bool)end),
	C = spawn(fun()->c(B,M)end),
	sleep(1000),
	status(b,B),
	status(c,C). 

a() ->
	process_flag(trap_exit,true),
	wait(a). 

b(A,Bool) ->
	process_flag(trap_exit,Bool),
	link(A),
	wait(b). 

c(B,M) ->
	link(B),
	case M of
		{die,Reason}->
			exit(Reason);
		{divide,N}->
			_=1/N,
			wait(c);
		normal->
			true
	end. 

wait(Prog) ->
	receive
		Any ->
			io:format("Process ~p received ~p~n",[Prog,Any]),
			wait(Prog)
	end. 

sleep(T) ->
	receive
	after T->true
	end. 

status(Name,Pid) ->
	case erlang:is_process_alive(Pid) of
		true ->
			io:format("Process ~p (~p) is alive~n",[Name,Pid]);
		false ->
			io:format("Process ~p (~p) is dead~n",[Name,Pid])
	end.