-spec cancel_timer(Ref) -> RemainingTime | false
                      when Ref :: reference(), RemainingTime :: non_neg_integer().

Cancel an internal timer in a generic FSM.

Cancels an internal timer referred by Ref in the gen_fsm process that calls this function.

Ref is a reference returned from send_event_after/2 or start_timer/2.

If the timer has already timed out, but the event not yet been delivered, it is cancelled as if it had not timed out, so there is no false timer event after returning from this function.

Returns the remaining time in milliseconds until the timer would have expired if Ref referred to an active timer, otherwise false.

-spec enter_loop(Module, Options, StateName, StateData) -> no_return()
                    when
                        Module :: module(),
                        Options :: [enter_loop_opt()],
                        StateName :: atom(),
                        StateData :: term().

Enter the gen_fsm receive loop.

Equivalent to enter_loop/6 with Timeout = infinity but the started server is not registered as for start_link/3.

-spec enter_loop(Module, Options, StateName, StateData, FsmName) -> no_return()
                    when
                        Module :: module(),
                        Options :: [enter_loop_opt()],
                        StateName :: atom(),
                        StateData :: term(),
                        FsmName :: fsm_name();
                (Module, Options, StateName, StateData, Timeout) -> no_return()
                    when
                        Module :: module(),
                        Options :: enter_loop_opt(),
                        StateName :: atom(),
                        StateData :: term(),
                        Timeout :: timeout().

Enter the gen_fsm receive loop.

With argument FsmName equivalent to enter_loop/6 with Timeout = infinity.

With argument Timeout equivalent to enter_loop/6 but the started server is not registered as for start_link/3.

-spec enter_loop(Module, Options, StateName, StateData, FsmName, Timeout) -> no_return()
                    when
                        Module :: module(),
                        Options :: [enter_loop_opt()],
                        StateName :: atom(),
                        StateData :: term(),
                        FsmName :: fsm_name() | pid(),
                        Timeout :: timeout().

Enter the gen_fsm receive loop.

Makes an existing process into a gen_fsm process. Does not return, instead the calling process enters the gen_fsm receive loop and becomes a gen_fsm process. The process must have been started using one of the start functions in proc_lib. The user is responsible for any initialization of the process, including registering a name for it.

This function is useful when a more complex initialization procedure is needed than the gen_fsm behavior provides.

Module, Options, and FsmName have the same meanings as when calling start[_link]/3,4. However, the process must have been registered according to FsmName before this function is called.

StateName, StateData, and Timeout have the same meanings as in the return value of Module:init/1. The callback module Module does not need to export an init/1 function.

The function fails if the calling process was not started by a proc_lib start function, or if it is not registered according to FsmName.

-spec reply(Caller, Reply) -> Result when Caller :: from(), Reply :: term(), Result :: term().

Send a reply to a caller.

This function can be used by a gen_fsm process to explicitly send a reply to a client process that called sync_send_event/2,3 or sync_send_all_state_event/2,3 when the reply cannot be defined in the return value of Module:StateName/3 or Module:handle_sync_event/4.

Caller must be the From argument provided to the callback function. Reply is any term given back to the client as the return value of sync_send_event/2,3 or sync_send_all_state_event/2,3.

Return value Result is not further defined, and is always to be ignored.

-spec send_all_state_event(FsmRef, Event) -> ok when FsmRef :: fsm_ref(), Event :: term().

Send an event asynchronously to a generic FSM.

Sends an event asynchronously to the FsmRef of the gen_fsm process and returns ok immediately. The gen_fsm process calls Module:handle_event/3 to handle the event.

For a description of the arguments, see send_event/2.

The difference between send_event/2 and send_all_state_event/2 is which callback function is used to handle the event. This function is useful when sending events that are handled the same way in every state, as only one handle_event clause is needed to handle the event instead of one clause in each state name function.

-spec send_event(FsmRef, Event) -> ok when FsmRef :: fsm_ref(), Event :: term().

Send an event asynchronously to a generic FSM.

Sends Event to the FsmRef of the gen_fsm process and returns ok immediately. The gen_fsm process calls Module:StateName/2 to handle the event, where StateName is the name of the current state of the gen_fsm process.

FsmRef can be any of the following:

• The pid/0
• Name, if the gen_fsm process is locally registered
• {Name, Node}, if the gen_fsm process is locally registered at another node
• {global, GlobalName}, if the gen_fsm process is globally registered
• {via, Module, ViaName}, if the gen_fsm process is registered through an alternative process registry

Event is any term that is passed as one of the arguments to Module:StateName/2.

-spec send_event_after(Time, Event) -> Ref
                          when Time :: non_neg_integer(), Event :: term(), Ref :: reference().

Send a delayed event internally in a generic FSM.

Sends a delayed event internally in the gen_fsm process that calls this function after Time milliseconds. Returns immediately a reference that can be used to cancel the delayed send using cancel_timer/1.

The gen_fsm process calls Module:StateName/2 to handle the event, where 'StateName' is the name of the current state of the gen_fsm process at the time the delayed event is delivered.

Event is any term that is passed as one of the arguments to Module:StateName/2.

-spec start(Module, Args, Options) -> Result
               when
                   Module :: module(),
                   Args :: term(),
                   Options :: [start_opt()],
                   Result :: {ok, Pid} | ignore | {error, Reason},
                   Pid :: pid(),
                   Reason :: term().

Create a standalone gen_fsm process, not registered.

Equivalent to start(Name, Mod, Args, Options) without registering a Name.

For a description of arguments and return values, see start_link/3,4.

-spec start(FsmName, Module, Args, Options) -> Result
               when
                   FsmName :: fsm_name(),
                   Module :: module(),
                   Args :: term(),
                   Options :: [start_opt()],
                   Result :: {ok, Pid} | ignore | {error, Reason},
                   Pid :: pid(),
                   Reason :: {already_started, Pid} | term().

Create a standalone gen_fsm process.

The created process is not part of a supervision tree and thus has no supervisor.

For a description of arguments and return values, see start_link/3,4.

-spec start_link(Module, Args, Options) -> Result
                    when
                        Module :: module(),
                        Args :: term(),
                        Options :: [start_opt()],
                        Result :: {ok, Pid} | ignore | {error, Reason},
                        Pid :: pid(),
                        Reason :: term().

Create a gen_fsm process in a supervision tree, not registered.

Equivalent to start_link(Name, Mod, Args, Options) without registering a Name.

-spec start_link(FsmName, Module, Args, Options) -> Result
                    when
                        FsmName :: fsm_name(),
                        Module :: module(),
                        Args :: term(),
                        Options :: [start_opt()],
                        Result :: {ok, Pid} | ignore | {error, Reason},
                        Pid :: pid(),
                        Reason :: {already_started, Pid} | term().

Create a gen_fsm process in a supervision tree.

The process is created as part of a supervision tree. The function is to be called, directly or indirectly, by the supervisor. For example, it ensures that the gen_fsm process is linked to the supervisor.

The gen_fsm process calls Module:init/1 to initialize. To ensure a synchronized startup procedure, start_link/3,4 does not return until Module:init/1 has returned.

• If FsmName = {local, Name}, the gen_fsm process is registered locally as Name using register/2.

• If FsmName = {global, GlobalName}, the gen_fsm process is registered globally as GlobalName using global:register_name/2.

• If FsmName = {via, Module, ViaName}, the gen_fsm process registers with the registry represented by Module. The Module callback is to export the functions register_name/2, unregister_name/1, whereis_name/1, and send/2, which are to behave like the corresponding functions in global. Thus, {via, global, GlobalName} is a valid reference.

Module is the name of the callback module.

Args is any term that is passed as the argument to Module:init/1.

If option {timeout, Time} is present, the gen_fsm process is allowed to spend Time milliseconds initializing or it terminates and the start function returns {error, timeout}.

If option {debug, Dbgs} is present, the corresponding sys function is called for each item in Dbgs; see sys(3).

If option {spawn_opt, SOpts} is present, SOpts is passed as option list to the spawn_opt BIF that is used to spawn the gen_fsm process; see spawn_opt/2.

Note

Using spawn option monitor is not allowed, it causes the function to fail with reason badarg.

If the gen_fsm process is successfully created and initialized, the function returns {ok, Pid}, where Pid is the pid of the gen_fsm process. If a process with the specified FsmName exists already, the function returns {error, {already_started, Pid}}, where Pid is the pid of that process.

If Module:init/1 fails with Reason, the function returns {error, Reason}. If Module:init/1 returns {stop, Reason} or ignore, the process is terminated and the function returns {error, Reason} or ignore, respectively.

-spec start_timer(Time, Msg) -> Ref when Time :: non_neg_integer(), Msg :: term(), Ref :: reference().

Send a time-out event internally in a generic FSM.

Sends a time-out event internally in the gen_fsm process that calls this function after Time milliseconds. Returns immediately a reference that can be used to cancel the timer using cancel_timer/1.

The gen_fsm process calls Module:StateName/2 to handle the event, where 'StateName' is the name of the current state of the gen_fsm process at the time the time-out message is delivered.

Msg is any term that is passed in the time-out message, {timeout, Ref, Msg}, as one of the arguments to Module:StateName/2.

-spec stop(FsmRef) -> ok when FsmRef :: fsm_ref().

Equivalent to stop(FsmRef, normal, infinity).

-spec stop(FsmRef, Reason, Timeout) -> ok
              when FsmRef :: fsm_ref(), Reason :: term(), Timeout :: timeout().

Synchronously stop a generic FSM.

Orders a generic finite state machine to exit with the specified Reason and waits for it to terminate. The gen_fsm process calls Module:terminate/3 before exiting.

The function returns ok if the generic finite state machine terminates with the expected reason. Any other reason than normal, shutdown, or {shutdown, Term} causes an error report to be issued using error_logger:format/2.

Timeout is an integer greater than zero that specifies how many milliseconds to wait for the generic FSM to terminate, or the atom infinity to wait indefinitely. If the generic finite state machine has not terminated within the specified time, a timeout exception is raised.

If the process does not exist, a noproc exception is raised.

-spec sync_send_all_state_event(FsmRef, Event) -> Reply
                                   when FsmRef :: fsm_ref(), Event :: term, Reply :: term().

Equivalent to sync_send_all_state_event(FsmRef, Event, 5000).

-spec sync_send_all_state_event(FsmRef, Event, Timeout) -> Reply
                                   when
                                       FsmRef :: fsm_ref(),
                                       Event :: term(),
                                       Timeout :: timeout(),
                                       Reply :: term().

Send an event synchronously to a generic FSM.

Sends an event to the FsmRef of the gen_fsm process and waits until a reply arrives or a time-out occurs. The gen_fsm process calls Module:handle_sync_event/4 to handle the event.

For a description of FsmRef and Event, see send_event/2. For a description of Timeout and Reply, see sync_send_event/3.

For a discussion about the difference between sync_send_event and sync_send_all_state_event, see send_all_state_event/2.

-spec sync_send_event(FsmRef, Event) -> Reply when FsmRef :: fsm_ref(), Event :: term(), Reply :: term().

Equivalent to sync_send_event(FsmRef, Event, 5000).

-spec sync_send_event(FsmRef, Event, Timeout) -> Reply
                         when
                             FsmRef :: fsm_ref(), Event :: term(), Timeout :: timeout(), Reply :: term().

Send an event synchronously to a generic FSM.

Sends an event to the FsmRef of the gen_fsm process and waits until a reply arrives or a time-out occurs. The gen_fsm process calls Module:StateName/3 to handle the event, where 'StateName' is the name of the current state of the gen_fsm process.

For a description of FsmRef and Event, see send_event/2.

Timeout is an integer greater than zero that specifies how many milliseconds to wait for a reply, or the atom infinity to wait indefinitely. If no reply is received within the specified time, the function call fails.

Return value Reply is defined in the return value of Module:StateName/3

Note

The ancient behavior of sometimes consuming the server exit message if the server died during the call while linked to the client was removed in Erlang 5.6/OTP R12B.