timer(3erl)						     Erlang Module Definition						       timer(3erl)

NAME

       timer - Timer Functions

DESCRIPTION

       This  module  provides useful functions related to time. Unless otherwise stated, time is always measured in milliseconds . All timer func-
       tions return immediately, regardless of work carried out by another process.

       Successful evaluations of the timer functions yield return values containing a timer reference, denoted TRef below. By using cancel/1 , the
       returned reference can be used to cancel any requested action. A TRef is an Erlang term, the contents of which must not be altered.

       The timeouts are not exact, but should be at least as long as requested.

EXPORTS

       start() -> ok

	      Starts  the  timer  server.  Normally, the server does not need to be started explicitly. It is started dynamically if it is needed.
	      This is useful during development, but in a target system the server should be started explicitly. Use configuration parameters  for
	      kernel for this.

       apply_after(Time, Module, Function, Arguments) -> {ok, Tref} | {error, Reason}

	      Types  Time = integer() in Milliseconds
		     Module = Function = atom()
		     Arguments = [term()]

	      Evaluates apply(M, F, A) after Time amount of time has elapsed. Returns {ok, TRef} , or {error, Reason} .

       send_after(Time, Pid, Message) -> {ok, TRef} | {error,Reason}
       send_after(Time, Message) -> {ok, TRef} | {error,Reason}

	      Types  Time = integer() in Milliseconds
		     Pid = pid() | atom()
		     Message = term()
		     Result = {ok, TRef} | {error, Reason}

		send_after/3 :
		  Evaluates  Pid  !  Message  after Time amount of time has elapsed. ( Pid can also be an atom of a registered name.) Returns {ok,
		  TRef} , or {error, Reason} .

		send_after/2 :
		  Same as send_after(Time, self(), Message) .

       exit_after(Time, Pid, Reason1) -> {ok, TRef} | {error,Reason2}
       exit_after(Time, Reason1) -> {ok, TRef} | {error,Reason2}
       kill_after(Time, Pid)-> {ok, TRef} | {error,Reason2}
       kill_after(Time) -> {ok, TRef} | {error,Reason2}

	      Types  Time = integer() in milliseconds
		     Pid = pid() | atom()
		     Reason1 = Reason2 = term()

		exit_after/3 :
		  Send an exit signal with reason Reason1 to Pid Pid . Returns {ok, TRef} , or {error, Reason2} .

		exit_after/2 :
		  Same as exit_after(Time, self(), Reason1) .

		kill_after/2 :
		  Same as exit_after(Time, Pid, kill) .

		kill_after/1 :
		  Same as exit_after(Time, self(), kill) .

       apply_interval(Time, Module, Function, Arguments) -> {ok, TRef} | {error, Reason}

	      Types  Time = integer() in milliseconds
		     Module = Function = atom()
		     Arguments = [term()]

	      Evaluates apply(Module, Function, Arguments) repeatedly at intervals of Time . Returns {ok, TRef} , or {error, Reason} .

       send_interval(Time, Pid, Message) -> {ok, TRef} | {error, Reason}
       send_interval(Time, Message) -> {ok, TRef} | {error, Reason}

	      Types  Time = integer() in milliseconds
		     Pid = pid() | atom()
		     Message = term()
		     Reason = term()

		send_interval/3 :
		  Evaluates Pid ! Message repeatedly after Time amount of time has elapsed. ( Pid can also be  an  atom  of  a	registered  name.)
		  Returns {ok, TRef} or {error, Reason} .

		send_interval/2 :
		  Same as send_interval(Time, self(), Message) .

       cancel(TRef) -> {ok, cancel} | {error, Reason}

	      Cancels  a  previously  requested timeout. TRef is a unique timer reference returned by the timer function in question. Returns {ok,
	      cancel} , or {error, Reason} when TRef is not a timer reference.

       sleep(Time) -> ok

	      Types  Time = integer() in milliseconds or the atom infinity

	      Suspends the process calling this function for Time amount of milliseconds and then returns ok , or suspend the process  forever	if
	      Time is the atom infinity . Naturally, this function does not return immediately.

       tc(Module, Function, Arguments) -> {Time, Value}
       tc(Fun, Arguments) -> {Time, Value}

	      Types  Module = Function = atom()
		     Fun = fun()
		     Arguments = [term()]
		     Time = integer() in microseconds
		     Value = term()

		tc/3 :
		  Evaluates  apply(Module,  Function, Arguments) and measures the elapsed real time as reported by now/0 . Returns {Time, Value} ,
		  where Time is the elapsed real time in microseconds , and Value is what is returned from the apply.

		tc/2 :
		  Evaluates apply(Fun, Arguments) . Otherwise works like tc/3 .

       now_diff(T2, T1) -> Tdiff

	      Types  T1 = T2 = {MegaSecs, Secs, MicroSecs}
		     Tdiff = MegaSecs = Secs = MicroSecs = integer()

	      Calculates the time difference Tdiff = T2 - T1 in microseconds , where T1  and  T2  probably  are  timestamp  tuples  returned  from
	      erlang:now/0 .

       seconds(Seconds) -> Milliseconds

	      Returns the number of milliseconds in Seconds .

       minutes(Minutes) -> Milliseconds

	      Return the number of milliseconds in Minutes .

       hours(Hours) -> Milliseconds

	      Returns the number of milliseconds in Hours .

       hms(Hours, Minutes, Seconds) -> Milliseconds

	      Returns the number of milliseconds in Hours + Minutes + Seconds .

EXAMPLES

       This example illustrates how to print out "Hello World!" in 5 seconds:

	     1> timer:apply_after(5000, io, format, ["~nHello World!~n", []]).
	     {ok,TRef}
	     Hello World!

       The  following  coding  example	illustrates a process which performs a certain action and if this action is not completed within a certain
       limit, then the process is killed.

	     Pid = spawn(mod, fun, [foo, bar]),
	     %% If pid is not finished in 10 seconds, kill him
	     {ok, R} = timer:kill_after(timer:seconds(10), Pid),
	     ...
	     %% We change our mind...
	     timer:cancel(R),
	     ...

WARNING

       A timer can always be removed by calling cancel/1 .

       An interval timer, i.e. a timer created by evaluating any of the functions apply_interval/4 , send_interval/3 , and  send_interval/2  ,	is
       linked to the process towards which the timer performs its task.

       A  one-shot  timer,  i.e.  a  timer created by evaluating any of the functions apply_after/4 , send_after/3 , send_after/2 , exit_after/3 ,
       exit_after/2 , kill_after/2 , and kill_after/1 is not linked to any process. Hence, such a timer is removed only when it reaches its  time-
       out, or if it is explicitly removed by a call to cancel/1 .

Ericsson AB							   stdlib 1.17.3						       timer(3erl)