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<HTML>
<HEAD>
<!-- refpage -->
<TITLE>gen_fsm</TITLE>
</HEAD>
<BODY BGCOLOR="#FFFFFF">
<CENTER>
<A HREF="http://www.erlang.se"><IMG BORDER=0 ALT="[Erlang Systems]" SRC="min_head.gif"></A>
<H1>gen_fsm</H1>
</CENTER>
<H3>MODULE</H3>
<UL>
gen_fsm</UL>
<H3>MODULE SUMMARY</H3>
<UL>
Generic Finite State Machine Behaviour</UL>
<H3>DESCRIPTION</H3>
<UL>
<P>A behaviour module for implementing a finite state machine.
A generic finite state machine process (gen_fsm) implemented
using this module will have a standard set of interface functions
and include functionality for tracing and error reporting. It will
also fit into an OTP supervision tree. Refer to <STRONG>OTP Design
Principles</STRONG> for more information.<P>A gen_fsm assumes all specific parts to be located in a callback
module exporting a pre-defined set of functions. The relationship
between the behaviour functions and the callback functions can be
illustrated as follows:<PRE>gen_fsm module Callback module
-------------- ---------------
gen_fsm:start_link -----> Module:init/1
gen_fsm:send_event -----> Module:StateName/2
gen_fsm:send_all_state_event -----> Module:handle_event/3
gen_fsm:sync_send_event -----> Module:StateName/3
gen_fsm:sync_send_all_state_event -----> Module:handle_sync_event/4
- -----> Module:handle_info/3
- -----> Module:terminate/3
- -----> Module:code_change/4
</PRE>
<P>If a callback function fails or returns a bad value, the gen_fsm
will terminate.<P>The <CODE>sys</CODE> module can be used for debugging a gen_fsm.<P>Note that a gen_fsm does not trap exit signals automatically,
this must be explicitly initiated in the callback module.<P>Unless otherwise stated, all functions in this module fail if
the specified gen_fsm does not exist or if bad arguments are given.</UL>
<H3>EXPORTS</H3>
<P><A NAME="start%3"><STRONG><CODE>start(Module, Args, Options) -> Result</CODE></STRONG></A><BR>
<A NAME="start%4"><STRONG><CODE>start(FsmName, Module, Args, Options) -> Result</CODE></STRONG></A><BR>
<A NAME="start_link%3"><STRONG><CODE>start_link(Module, Args, Options) -> Result</CODE></STRONG></A><BR>
<A NAME="start_link%4"><STRONG><CODE>start_link(FsmName, Module, Args, Options) -> Result</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>FsmName = {local,Name} | {global,Name}</CODE></STRONG><BR>
<STRONG><CODE> Name = atom()</CODE></STRONG><BR>
<STRONG><CODE>Module = atom()</CODE></STRONG><BR>
<STRONG><CODE>Args = term()</CODE></STRONG><BR>
<STRONG><CODE>Options = [Option]</CODE></STRONG><BR>
<STRONG><CODE> Option = {debug,Dbgs} | {timeout,Time}</CODE></STRONG><BR>
<STRONG><CODE>  Dbgs = [Dbg]</CODE></STRONG><BR>
<STRONG><CODE>   Dbg = trace | log | statistics</CODE></STRONG><BR>
<STRONG><CODE>    | {log_to_file,FileName}
| {install,{Func,FuncState}}</CODE></STRONG><BR>
<STRONG><CODE>Result = {ok,Pid} | ignore | {error,Error}</CODE></STRONG><BR>
<STRONG><CODE> Pid = pid()</CODE></STRONG><BR>
<STRONG><CODE> Error = {already_started,Pid} | term()</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>Creates a gen_fsm process which calls <CODE>Module:init/1</CODE> to
initialize. To ensure a synchronized start-up procedure, this
function does not return until <CODE>Module:init/1</CODE> has returned.
<P>A gen_fsm started using <CODE>start_link</CODE> is linked to
the calling process, this function must be used if the gen_fsm is
included in a supervision tree. A gen_fsm started using
<CODE>start</CODE> is not linked to the calling process.<P>If <CODE>FsmName={local,Name}</CODE>, the gen_fsm is registered
locally as <CODE>Name</CODE> using <CODE>register/2</CODE>.
If <CODE>FsmName={global,Name}</CODE>, the gen_fsm is registered
globally as <CODE>Name</CODE> using <CODE>global:register_name/2</CODE>.
If no name is provided, the gen_fsm is not registered.<P><CODE>Module</CODE> is the name of the callback module.<P><CODE>Args</CODE> is an arbitrary term which is passed as the argument
to <CODE>Module:init/1</CODE>.<P>If the option <CODE>{timeout,Time}</CODE> is present, the gen_fsm
is allowed to spend <CODE>Time</CODE> milliseconds initializing
or it will be terminated and the start function will return
<CODE>{error,timeout}</CODE>.<P>If the option <CODE>{debug,Dbgs}</CODE> is present, the corresponding
<CODE>sys</CODE> function will be called for each item in <CODE>Dbgs</CODE>.
Refer to <CODE>sys(3)</CODE> for more information.<P>If the gen_fsm is successfully created and initialized
the function returns <CODE>{ok,Pid}</CODE>, where <CODE>Pid</CODE> is
the pid of the gen_fsm. If there already exists a process with
the specified <CODE>FsmName</CODE>, the function returns
<CODE>{error,{already_started,Pid}}</CODE> where <CODE>Pid</CODE> is the pid
of that process.<P>If <CODE>Module:init/1</CODE> fails with <CODE>Reason</CODE>, the function
returns <CODE>{error,Reason}</CODE>. If <CODE>Module:init/1</CODE> returns
<CODE>{stop,Reason}</CODE> or <CODE>ignore</CODE>, the process is terminated
and the function returns <CODE>{error,Reason}</CODE> or <CODE>ignore</CODE>,
respectively.</UL>
<P><A NAME="send_event%2"><STRONG><CODE>send_event(FsmRef, Event) -> ok</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>FsmRef = Name | {Name,Node} | {global,Name} | pid()</CODE></STRONG><BR>
<STRONG><CODE> Name = Node = atom()</CODE></STRONG><BR>
<STRONG><CODE>Event = term()</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>Sends an event asynchronously to the gen_fsm <CODE>FsmRef</CODE>
and returns <CODE>ok</CODE> immediately. The gen_fsm will call
<CODE>Module:StateName/2</CODE> to handle the event, where
<CODE>StateName</CODE> is the name of the current state of the gen_fsm.
<P><CODE>FsmRef</CODE> can be:<P><UL>
<LI>the pid,</LI><BR>
<LI><CODE>Name</CODE>, if the gen_fsm is locally registered,</LI><BR>
<LI><CODE>{Name,Node}</CODE>, if the gen_fsm is locally registered at
another node, or</LI><BR>
<LI><CODE>{global,Name}</CODE>, if the gen_fsm is globally registered.
</LI><BR>
</UL>
<P><CODE>Event</CODE> is an arbitrary term which is passed as one of
the arguments to <CODE>Module:StateName/2</CODE>.</UL>
<P><A NAME="send_all_state_event%2"><STRONG><CODE>send_all_state_event(FsmRef, Event) -> ok</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>FsmRef = Name | {Name,Node} | {global,Name} | pid()</CODE></STRONG><BR>
<STRONG><CODE> Name = Node = atom()</CODE></STRONG><BR>
<STRONG><CODE>Event = term()</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>Sends an event asynchronously to the gen_fsm <CODE>FsmRef</CODE>
and returns <CODE>ok</CODE> immediately. The gen_fsm will call
<CODE>Module:handle_event/3</CODE> to handle the event.<P>See <CODE>send_event/2</CODE> for a description of the arguments.<P>The difference between <CODE>send_event</CODE> and
<CODE>send_all_state_event</CODE> 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
<CODE>handle_event</CODE> clause is needed to handle the event instead
of one clause in each state name function.</UL>
<P><A NAME="sync_send_event%2"><STRONG><CODE>sync_send_event(FsmRef, Event) -> Reply</CODE></STRONG></A><BR>
<A NAME="sync_send_event%3"><STRONG><CODE>sync_send_event(FsmRef, Event, Timeout) -> Reply</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>FsmRef = Name | {Name,Node} | {global,Name} | pid()</CODE></STRONG><BR>
<STRONG><CODE> Name = Node = atom()</CODE></STRONG><BR>
<STRONG><CODE>Event = term()</CODE></STRONG><BR>
<STRONG><CODE>Timeout = int()>0 | infinity</CODE></STRONG><BR>
<STRONG><CODE>Reply = term()</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>Sends an event to the gen_fsm <CODE>FsmRef</CODE> and waits until a
reply arrives or a timeout occurs. The gen_fsm will call
<CODE>Module:StateName/3</CODE> to handle the event, where
<CODE>StateName</CODE> is the name of the current state of the gen_fsm.
<P>See <CODE>send_event/2</CODE> for a description of <CODE>FsmRef</CODE> and
<CODE>Event</CODE>.<P><CODE>Timeout</CODE> is an integer greater than zero which specifies
how many milliseconds to wait for a reply, or the atom
<CODE>infinity</CODE> to wait indefinitely. Default value is 5000.
If no reply is received within the specified time, the function
call fails.<P>The return value <CODE>Reply</CODE> is defined in the return value of
<CODE>Module:StateName/3</CODE>.<P>In the case where the gen_fsm terminates during the handling of
the event and the caller is linked to the gen_fsm and trapping
exits, the exit message is removed from the caller's receive
queue before the function call fails.<BR>
This behaviour is retained for backwards compatibility only and may
change in the future. Note that if the gen_fsm crashes in between
calls, a linked process must take care of the exit message anyway.
<BR>
Warning: Under certain circumstances
(e.g. <CODE>FsmRef = {Name,Node}</CODE>, and <CODE>Node</CODE> goes down)
the exit message cannot be removed.</UL>
<P><A NAME="sync_send_all_state_event%2"><STRONG><CODE>sync_send_all_state_event(FsmRef, Event) -> Reply</CODE></STRONG></A><BR>
<A NAME="sync_send_all_state_event%3"><STRONG><CODE>sync_send_all_state_event(FsmRef, Event, Timeout) -> Reply</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>FsmRef = Name | {Name,Node} | {global,Name} | pid()</CODE></STRONG><BR>
<STRONG><CODE> Name = Node = atom()</CODE></STRONG><BR>
<STRONG><CODE>Event = term()</CODE></STRONG><BR>
<STRONG><CODE>Timeout = int()>0 | infinity</CODE></STRONG><BR>
<STRONG><CODE>Reply = term()</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>Sends an event to the gen_fsm <CODE>FsmRef</CODE> and waits until a
reply arrives or a timeout occurs. The gen_fsm will call
<CODE>Module:handle_event/3</CODE> to handle the event.<P>See <CODE>send_event/2</CODE> for a description of <CODE>FsmRef</CODE> and
<CODE>Event</CODE>. See <CODE>sync_send_event/3</CODE> for a description of
<CODE>Timeout</CODE> and <CODE>Reply</CODE>.<P>See <CODE>send_all_state_event/2</CODE> for a discussion about
the difference between <CODE>sync_send_event</CODE> and
<CODE>sync_send_all_state_event</CODE>.</UL>
<P><A NAME="reply%2"><STRONG><CODE>reply(Caller, Reply) -> true</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>Caller - see below</CODE></STRONG><BR>
<STRONG><CODE>Reply = term()</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>This function can be used by a gen_fsm to explicitly send a reply
to a client process that called <CODE>sync_send_event</CODE> or
<CODE>sync_send_all_state_event</CODE>, when the reply cannot be defined
in the return value of <CODE>Module:State/3</CODE> or
<CODE>Module:handle_sync_event/4</CODE>.<P><CODE>Caller</CODE> must be the <CODE>From</CODE> argument provided to
the callback function. <CODE>Reply</CODE> is an arbitrary term, which
will be given back to the client as the return value of
<CODE>sync_send_event</CODE> or <CODE>sync_send_all_state_event</CODE>.</UL>
<H3>CALLBACK FUNCTIONS</H3>
<UL>
<P>The following functions should be exported from a <CODE>gen_fsm</CODE>
callback module.<P>In the description, the expression <STRONG>state name</STRONG> is used to
denote a state of the state machine. <STRONG>state data</STRONG> is used to
denote the internal state of the Erlang process which implements
the state machine.<P> </UL>
<H3>EXPORTS</H3>
<P><A NAME="Module:init%1"><STRONG><CODE>Module:init(Args) -> Result</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>Args = term()</CODE></STRONG><BR>
<STRONG><CODE>Return = {ok,StateName,StateData}
| {ok,StateName,StateData,Timeout}</CODE></STRONG><BR>
<STRONG><CODE> | {stop,Reason} | ignore</CODE></STRONG><BR>
<STRONG><CODE> StateName = atom()</CODE></STRONG><BR>
<STRONG><CODE> StateData = term()</CODE></STRONG><BR>
<STRONG><CODE> Timeout = int()>0 | infinity</CODE></STRONG><BR>
<STRONG><CODE> Reason = term()</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>Whenever a gen_fsm is started using <CODE>gen_fsm:start/3,4</CODE> or
<CODE>gen_fsm:start_link/3,4</CODE>, this function is called by the new
process to initialize.<P><CODE>Args</CODE> is the <CODE>Args</CODE> argument provided to the start
function.<P>If initialization is successful, the function should return
<CODE>{ok,StateName,StateData}</CODE> or
<CODE>{ok,StateName,StateData,Timout}</CODE>, where <CODE>StateName</CODE>
is the initial state name and <CODE>StateData</CODE> the initial
state data of the gen_fsm.<P>If an integer timout value is provided, a timout will occur
unless an event or a message is received within <CODE>Timeout</CODE>
milliseconds. A timout is represented by the atom <CODE>timeout</CODE>
and should be handled by the <CODE>Module:StateName/2</CODE> callback
functions. The atom <CODE>inifinity</CODE> can be used to wait
indefinitely, this is the default value.<P>If something goes wrong during the initialization the function
should return <CODE>{stop,Reason}</CODE>, where <CODE>Reason</CODE> is any
term, or <CODE>ignore</CODE>.</UL>
<P><A NAME="Module:StateName%2"><STRONG><CODE>Module:StateName(Event, StateData) -> Result</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>Event = timeout | term()</CODE></STRONG><BR>
<STRONG><CODE>StateData = term()</CODE></STRONG><BR>
<STRONG><CODE>Result = {next_state,NextStateName,NewStateData} |
{next_state,NextStateName,NewStateData,Timeout}</CODE></STRONG><BR>
<STRONG><CODE>  | {stop,Reason,NewStateData}</CODE></STRONG><BR>
<STRONG><CODE> NextStateName = atom()</CODE></STRONG><BR>
<STRONG><CODE> NewStateData = term()</CODE></STRONG><BR>
<STRONG><CODE> Timeout = int()>0 | infinity</CODE></STRONG><BR>
<STRONG><CODE> Reason = term()</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>There should be one instance of this function for each possible
state name. Whenever a gen_fsm receives an event sent using
<CODE>gen_fsm:send_event/2</CODE>, the instance of this function with
the same name as the current state name <CODE>StateName</CODE> is called
to handle the event. It is also called if a timeout occurs.<P><CODE>Event</CODE> is either the atom <CODE>timeout</CODE>, if a timeout has
occured, or the <CODE>Event</CODE> argument provided to
<CODE>send_event</CODE>.<P><CODE>StateData</CODE> is the state data of the gen_fsm.<P>If the function returns
<CODE>{next_state,NextStateName,NewStateData}</CODE> or
<CODE>{next_state,NextStateName,NewStateData,Timeout}</CODE>,
the gen_fsm will continue executing with the current state name
set to <CODE>NextStateName</CODE> and with the possibly updated state
data <CODE>NewStateData</CODE>.
See <CODE>Module:init/1</CODE> for a description of <CODE>Timeout</CODE>.<P>If the function returns <CODE>{stop,Reason,NewStateData}</CODE>,
the gen_fsm will call <CODE>Module:terminate(Reason,NewStateData)</CODE>
and terminate.</UL>
<P><A NAME="Module:handle_event%3"><STRONG><CODE>Module:handle_event(Event, StateName, StateData) -> Result</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>Event = term()</CODE></STRONG><BR>
<STRONG><CODE>StateName = atom()</CODE></STRONG><BR>
<STRONG><CODE>StateData = term()</CODE></STRONG><BR>
<STRONG><CODE>Result = {next_state,NextStateName,NewStateData} |
{next_state,NextStateName,NewStateData,Timeout}</CODE></STRONG><BR>
<STRONG><CODE>  | {stop,Reason,NewStateData}</CODE></STRONG><BR>
<STRONG><CODE> NextStateName = atom()</CODE></STRONG><BR>
<STRONG><CODE> NewStateData = term()</CODE></STRONG><BR>
<STRONG><CODE> Timeout = int()>0 | infinity</CODE></STRONG><BR>
<STRONG><CODE> Reason = term()</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>Whenever a gen_fsm receives an event sent using
<CODE>gen_fsm:send_all_state_event/2</CODE>, this function is called
to handle the event.<P><CODE>StateName</CODE> is the current state name of the gen_fsm.<P>See <CODE>Module:StateName/2</CODE> for a description of the other
arguments and possible return values.</UL>
<P><A NAME="Module:StateName%3"><STRONG><CODE>Module:StateName(Event, From, StateData) -> Result</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>Event = term()</CODE></STRONG><BR>
<STRONG><CODE>From = {pid(),Tag}</CODE></STRONG><BR>
<STRONG><CODE>StateData = term()</CODE></STRONG><BR>
<STRONG><CODE>Result = {reply,Reply,NextStateName,NewStateData} |
{reply,Reply,NextStateName,NewStateData,Timeout}</CODE></STRONG><BR>
<STRONG><CODE>  | {next_state,NextStateName,NewStateData} |
{next_state,NextStateName,NewStateData,Timeout}</CODE></STRONG><BR>
<STRONG><CODE>  | {stop,Reason,Reply,NewStateData} |
{stop,Reason,NewStateData}</CODE></STRONG><BR>
<STRONG><CODE> Reply = term()</CODE></STRONG><BR>
<STRONG><CODE> NextStateName = atom()</CODE></STRONG><BR>
<STRONG><CODE> NewStateData = term()</CODE></STRONG><BR>
<STRONG><CODE> Timeout = int()>0 | infinity</CODE></STRONG><BR>
<STRONG><CODE> Reason = normal | term()</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>There should be one instance of this function for each possible
state name. Whenever a gen_fsm receives an event sent using
<CODE>gen_fsm:sync_send_event/2,3</CODE>, the instance of this function
with the same name as the current state name <CODE>StateName</CODE> is
called to handle the event.<P><CODE>Event</CODE> is the <CODE>Event</CODE> argument provided to
<CODE>sync_send_event</CODE>.<P><CODE>From</CODE> is a tuple <CODE>{Pid,Tag}</CODE> where <CODE>Pid</CODE> is
the pid of the process which called <CODE>sync_send_event</CODE> and
<CODE>Tag</CODE> is a unique tag.<P><CODE>StateData</CODE> is the state data of the gen_fsm.<P>If the function returns
<CODE>{reply,Reply,NextStateName,NewStateData}</CODE> or
<CODE>{reply,Reply,NextStateName,NewStateData,Timeout}</CODE>,
<CODE>Reply</CODE> will be given back to <CODE>From</CODE> as the return value
of <CODE>sync_send_event</CODE>. The gen_fsm then continues executing
with the current state name set to <CODE>NextStateName</CODE> and with
the possibly updated state data <CODE>NewStateData</CODE>.
See <CODE>Module:init/1</CODE> for a description of <CODE>Timeout</CODE>.<P>If the function returns
<CODE>{next_state,NextStateName,NewStateData}</CODE> or
<CODE>{next_state,NextStateName,NewStateData,Timeout}</CODE>,
the gen_fsm will continue executing in <CODE>NextStateName</CODE> with
<CODE>NewStateData</CODE>. Any reply to <CODE>From</CODE> must be given
explicitly using <CODE>gen_fsm:reply/2</CODE>.<P>If the function returns <CODE>{stop,Reason,Reply,NewStateData}</CODE>,
<CODE>Reply</CODE> will be given back to <CODE>From</CODE>. If the function
returns <CODE>{stop,Reason,NewStateData}</CODE>, any reply to <CODE>From</CODE>
must be given explicitly using <CODE>gen_fsm:reply/2</CODE>. The gen_fsm
will then call <CODE>Module:terminate(Reason,NewStateData)</CODE> and
terminate.</UL>
<P><A NAME="Module:handle_sync_event%4"><STRONG><CODE>Module:handle_sync_event(Event, From, StateName, StateData)
-> Result
</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>Event = term()</CODE></STRONG><BR>
<STRONG><CODE>From = {pid(),Tag}</CODE></STRONG><BR>
<STRONG><CODE>StateName = atom()</CODE></STRONG><BR>
<STRONG><CODE>StateData = term()</CODE></STRONG><BR>
<STRONG><CODE>Result = {reply,Reply,NextStateName,NewStateData} |
{reply,Reply,NextStateName,NewStateData,Timeout}</CODE></STRONG><BR>
<STRONG><CODE>  | {next_state,NextStateName,NewStateData} |
{next_state,NextStateName,NewStateData,Timeout}</CODE></STRONG><BR>
<STRONG><CODE>  | {stop,Reason,Reply,NewStateData} |
{stop,Reason,NewStateData}</CODE></STRONG><BR>
<STRONG><CODE> Reply = term()</CODE></STRONG><BR>
<STRONG><CODE> NextStateName = atom()</CODE></STRONG><BR>
<STRONG><CODE> NewStateData = term()</CODE></STRONG><BR>
<STRONG><CODE> Timeout = int()>0 | infinity</CODE></STRONG><BR>
<STRONG><CODE> Reason = term()</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>Whenever a gen_fsm receives an event sent using
<CODE>gen_fsm:sync_send_all_state_event/2,3</CODE>, this function is
called to handle the event.<P><CODE>StateName</CODE> is the current state name of the gen_fsm.<P>See <CODE>Module:StateName/3</CODE> for a description of the other
arguments and possible return values.</UL>
<P><A NAME="Module:handle_info%3"><STRONG><CODE>Module:handle_info(Info, StateName, StateData) -> Result</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>Info = term()</CODE></STRONG><BR>
<STRONG><CODE>StateName = atom()</CODE></STRONG><BR>
<STRONG><CODE>StateData = term()</CODE></STRONG><BR>
<STRONG><CODE>Result = {next_state,NextStateName,NewStateData} |
{next_state,NextStateName,NewStateData,Timeout}</CODE></STRONG><BR>
<STRONG><CODE>  | {stop,Reason,NewStateData}</CODE></STRONG><BR>
<STRONG><CODE> NextStateName = atom()</CODE></STRONG><BR>
<STRONG><CODE> NewStateData = term()</CODE></STRONG><BR>
<STRONG><CODE> Timeout = int()>0 | infinity</CODE></STRONG><BR>
<STRONG><CODE> Reason = normal | term()</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>This function is called by a gen_fsm when it receives any other
message than a synchronous or asynchronous event (or a system
message).<P><CODE>Info</CODE> is the received message.<P>See <CODE>Module:StateName/2</CODE> for a description of the other
arguments and possible return values.</UL>
<P><A NAME="Module:terminate%3"><STRONG><CODE>Module:terminate(Reason, StateName, StateData)</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>Reason = normal | shutdown | term()</CODE></STRONG><BR>
<STRONG><CODE>StateName = atom()</CODE></STRONG><BR>
<STRONG><CODE>StateData = term()</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>This function is called by a gen_fsm when it is about to
terminate. It should be the opposite of <CODE>Module:init/1</CODE> and
do any necessary cleaning up. When it returns, the gen_fsm
terminates with <CODE>Reason</CODE>. The return value is ignored.<P><CODE>Reason</CODE> is a term denoting the stop reason, <CODE>StateName</CODE>
is the current state name, and <CODE>StateData</CODE> is the state data
of the gen_fsm.<P><CODE>Reason</CODE> depends on why the gen_fsm is terminating. If it is
because another callback function has returned a stop tuple
<CODE>{stop,..}</CODE>, <CODE>Reason</CODE> will have the value specified in
that tuple. If it is due to a failure, <CODE>Reason</CODE> is the error
reason.<P>If the gen_fsm is part of a supervision tree and is ordered
by its superviser to terminate, this function will be called with
<CODE>Reason=shutdown</CODE> if the following conditions apply:<P><UL>
<LI>the gen_fsm has been set to trap exit signals, and</LI><BR>
<LI>the shutdown strategy as defined in the supervisor's child
specification is an integer timeout value, not
<CODE>brutal_kill</CODE>.
</LI><BR>
</UL>
<P>Otherwise, the gen_fsm will be immediately terminated.<P>Note that for any other reason than <CODE>normal</CODE> or
<CODE>shutdown</CODE>, the gen_fsm is assumed to terminate due to an
error and an error report is issued using
<CODE>error_logger:format/2</CODE>.</UL>
<P><A NAME="Module:code_change%4"><STRONG><CODE>Module:code_change(OldVsn, StateName, StateData, Extra) ->
{ok, NextStateName, NewStateData}</CODE></STRONG></A><BR>
<P><UL>Types:
<UL>
<STRONG><CODE>OldVsn = undefined | term()</CODE></STRONG><BR>
<STRONG><CODE>StateName = NextStateName = atom()</CODE></STRONG><BR>
<STRONG><CODE>StateData = NewStateData = term()</CODE></STRONG><BR>
<STRONG><CODE>Extra = term()</CODE></STRONG><BR>
</UL>
</UL>
<UL>
<P>This function is called by a gen_fsm when it should update its
state data due to a code replacement, i.e. when the instruction
<CODE>{update,Module,Change,PrePurge,PostPurge,Modules}</CODE> where
<CODE>Change={advanced,Extra}</CODE> has been given to the release
handler. See <STRONG>SASL User's Guide</STRONG> for more information.<P><CODE>OldVsn</CODE> is the <CODE>vsn</CODE> attribute of the old version of
the callback module <CODE>Module</CODE>, or <CODE>undefined</CODE> if no
such attribute is defined.<P><CODE>StateName</CODE> is the current state name and <CODE>StateData</CODE>
the state data of the gen_fsm.<P><CODE>Extra</CODE> is the same as in the <CODE>{advanced,Extra}</CODE> part
of the update instruction.<P>The function should return the new current state name and updated
state data.</UL>
<H3>SEE ALSO</H3>
<UL>
<P>supervisor(3), sys(3)</UL>
<H3>AUTHORS</H3>
<UL>
Gunilla Hugosson - support@erlang.ericsson.se<BR>
</UL>
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