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)