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Diffstat (limited to 'erts/doc/src/erlang.xml')
| -rw-r--r-- | erts/doc/src/erlang.xml | 333 |
1 files changed, 259 insertions, 74 deletions
diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml index ba5f80a9c1..3fea64cef5 100644 --- a/erts/doc/src/erlang.xml +++ b/erts/doc/src/erlang.xml @@ -536,29 +536,108 @@ </desc> </func> <func> - <name name="cancel_timer" arity="1"/> + <name name="cancel_timer" arity="2"/> <fsummary>Cancel a timer</fsummary> <desc> - <p>Cancels a timer, where <c><anno>TimerRef</anno></c> was returned by - either - <seealso marker="#send_after/3">erlang:send_after/3</seealso> - or - <seealso marker="#start_timer/3">erlang:start_timer/3</seealso>. - If the timer is there to be removed, the function returns - the time in milliseconds left until the timer would have expired, - otherwise <c>false</c> (which means that <c><anno>TimerRef</anno></c> was - never a timer, that it has already been cancelled, or that it - has already delivered its message).</p> + <p> + Cancels a timer that has been created by either + <seealso marker="#start_timer/4"><c>erlang:start_timer()</c></seealso>, + or <seealso marker="#send_after/4"><c>erlang:send_after()</c></seealso>. + <c><anno>TimerRef</anno></c> identifies the timer, and + was returned by the BIF that created the timer. + </p> + <p>Currently available <c><anno>Option</anno></c>s:</p> + <taglist> + <tag><c>{async, Async}</c></tag> + <item> + <p> + Asynchronous request for cancellation. <c>Async</c> + defaults to <c>false</c> which will cause the + cancellation to be performed synchronously. When + <c>Async</c> is set to <c>true</c>, the cancel + operation will be performed asynchronously. That is, + <c>erlang:cancel_timer()</c> will send an asynchronous + request for cancellation to the timer service that + manages the timer, and then return <c>ok</c>. + </p> + </item> + <tag><c>{info, Info}</c></tag> + <item> + <p> + Request information about the <c><anno>Result</anno></c> + of the cancellation. <c>Info</c> defaults to <c>true</c> + which means that the <c><anno>Result</anno></c> will + be given. When <c>Info</c> is set to <c>false</c>, no + information about the result of the cancellation + will be given. When the operation is performed</p> + <taglist> + <tag>synchronously</tag> + <item> + <p> + If <c>Info</c> is <c>true</c>, the <c>Result</c> will + returned by <c>erlang:cancel_timer()</c>; otherwise, + <c>ok</c> will be returned. + </p> + </item> + <tag>asynchronously</tag> + <item> + <p> + If <c>Info</c> is <c>true</c>, a message on the form + <c>{cancel_timer, <anno>TimerRef</anno>, + <anno>Result</anno>}</c> will be sent to the + caller of <c>erlang:cancel_timer()</c> when the + cancellation operation has been performed; otherwise, + no message will be sent. + </p> + </item> + </taglist> + </item> + </taglist> + <p> + More <c><anno>Option</anno></c>s may be added in the future. + </p> + <p> + When the <c><anno>Result</anno></c> equals <c>false</c>, a + timer corresponding to <c><anno>TimerRef</anno></c> could not + be found. This can be either because the timer had expired, + already had been canceled, or because <c><anno>TimerRef</anno></c> + never has corresponded to a timer. If the timer has expired, + the timeout message has been sent, but it does not tell you + whether or not it has arrived at its destination yet. When the + <c><anno>Result</anno></c> is an integer, it represents the + time in milli-seconds left until the timer will expire. + </p> + <note> + <p> + The timer service that manages the timer may be co-located + with another scheduler than the scheduler that the calling + process is executing on. If this is the case, communication + with the timer service will take much longer time than if it + is located locally. If the calling process is in critical + path, and can do other things while waiting for the result + of this operation, or is not interested in the result of + the operation, you want to use the <c>{async, true}</c> + option. If using the <c>{async, false}</c> option, the calling + process will be blocked until the operation has been + performed. + </p> + </note> <p>See also - <seealso marker="#send_after/3">erlang:send_after/3</seealso>, - <seealso marker="#start_timer/3">erlang:start_timer/3</seealso>, + <seealso marker="#send_after/4"><c>erlang:send_after/4</c></seealso>, + <seealso marker="#start_timer/4"><c>erlang:start_timer/4</c></seealso>, and - <seealso marker="#read_timer/1">erlang:read_timer/1</seealso>.</p> - <p>Note: Cancelling a timer does not guarantee that the message - has not already been delivered to the message queue.</p> + <seealso marker="#read_timer/2"><c>erlang:read_timer/2</c></seealso>.</p> + </desc> + </func> + <func> + <name name="cancel_timer" arity="1"/> + <fsummary>Cancel a timer</fsummary> + <desc> + <p>Cancels a timer. The same as calling + <seealso marker="#cancel_timer/2"><c>erlang:cancel_timer(TimerRef, + [])</c></seealso>.</p> </desc> </func> - <func> <name name="check_old_code" arity="1"/> <fsummary>Check if a module has old code</fsummary> @@ -4505,23 +4584,77 @@ os_prompt% </pre> </desc> </func> <func> - <name name="read_timer" arity="1"/> - <fsummary>Number of milliseconds remaining for a timer</fsummary> - <desc> - <p><c><anno>TimerRef</anno></c> is a timer reference returned by - <seealso marker="#send_after/3">erlang:send_after/3</seealso> - or - <seealso marker="#start_timer/3">erlang:start_timer/3</seealso>. - If the timer is active, the function returns the time in - milliseconds left until the timer will expire, otherwise - <c>false</c> (which means that <c><anno>TimerRef</anno></c> was never a - timer, that it has been cancelled, or that it has already - delivered its message).</p> + <name name="read_timer" arity="2"/> + <fsummary>Read the state of a timer</fsummary> + <desc> + <p> + Read the state of a timer that has been created by either + <seealso marker="#start_timer/4"><c>erlang:start_timer()</c></seealso>, + or <seealso marker="#send_after/4"><c>erlang:send_after()</c></seealso>. + <c><anno>TimerRef</anno></c> identifies the timer, and + was returned by the BIF that created the timer. + </p> + <p>Currently available <c><anno>Option</anno>s</c>:</p> + <taglist> + <tag><c>{async, Async}</c></tag> + <item> + <p> + Asynchronous request for state information. <c>Async</c> + defaults to <c>false</c> which will cause the operation + to be performed synchronously. In this case, the <c>Result</c> + will be returned by <c>erlang:read_timer()</c>. When + <c>Async</c> is set to <c>true</c>, <c>erlang:read_timer()</c> + will send an asynchronous request for the state information + to the timer service that manages the timer, and then return + <c>ok</c>. A message on the format <c>{read_timer, + <anno>TimerRef</anno>, <anno>Result</anno>}</c> will be + sent to the caller of <c>erlang:read_timer()</c> when the + operation has been processed. + </p> + </item> + </taglist> + <p> + More <c><anno>Option</anno></c>s may be added in the future. + </p> + <p> + When the <c><anno>Result</anno></c> equals <c>false</c>, a + timer corresponding to <c><anno>TimerRef</anno></c> could not + be found. This can be either because the timer had expired, + had been canceled, or because <c><anno>TimerRef</anno></c> + never has corresponded to a timer. If the timer has expired, + the timeout message has been sent, but it does not tell you + whether or not it has arrived at its destination yet. When the + <c><anno>Result</anno></c> is an integer, it represents the + time in milli-seconds left until the timer will expire. + </p> + <note> + <p> + The timer service that manages the timer may be co-located + with another scheduler than the scheduler that the calling + process is executing on. If this is the case, communication + with the timer service will take much longer time than if it + is located locally. If the calling process is in critical + path, and can do other things while waiting for the result + of this operation you want to use the <c>{async, true}</c> + option. If using the <c>{async, false}</c> option, the calling + process will be blocked until the operation has been + performed. + </p> + </note> <p>See also - <seealso marker="#send_after/3">erlang:send_after/3</seealso>, - <seealso marker="#start_timer/3">erlang:start_timer/3</seealso>, + <seealso marker="#send_after/4"><c>erlang:send_after/4</c></seealso>, + <seealso marker="#start_timer/4"><c>erlang:start_timer/4</c></seealso>, and - <seealso marker="#cancel_timer/1">erlang:cancel_timer/1</seealso>.</p> + <seealso marker="#cancel_timer/2"><c>erlang:cancel_timer/2</c></seealso>.</p> + </desc> + </func> + <func> + <name name="read_timer" arity="1"/> + <fsummary>Read the state of a timer</fsummary> + <desc> + <p>Read the state of a timer. The same as calling + <seealso marker="#read_timer/2"><c>erlang:read_timer(TimerRef, + [])</c></seealso>.</p> </desc> </func> <func> @@ -4670,31 +4803,26 @@ true</pre> </desc> </func> <func> + <name name="send_after" arity="4"/> + <fsummary>Start a timer</fsummary> + <desc> + <p> + Starts a timer. When the timer expires, the message + <c><anno>Msg</anno></c> will be sent to the process + identified by <c><anno>Dest</anno></c>. Appart from + the format of the message sent to + <c><anno>Dest</anno></c> when the timer expires + <c>erlang:send_after/4</c> works exactly as + <seealso marker="#start_timer/4"><c>erlang:start_timer/4</c></seealso>.</p> + </desc> + </func> + <func> <name name="send_after" arity="3"/> - <type_desc variable="Time">0 <= Time <= 4294967295</type_desc> <fsummary>Start a timer</fsummary> <desc> - <p>Starts a timer which will send the message <c>Msg</c> - to <c><anno>Dest</anno></c> after <c><anno>Time</anno></c> milliseconds.</p> - <p>If <c><anno>Dest</anno></c> is a <c>pid()</c> it has to be a <c>pid()</c> of a local process, dead or alive.</p> - <p>The <c><anno>Time</anno></c> value can, in the current implementation, not be greater than 4294967295.</p> - <p>If <c><anno>Dest</anno></c> is an <c>atom()</c>, it is supposed to be the name of - a registered process. The process referred to by the name is - looked up at the time of delivery. No error is given if - the name does not refer to a process.</p> - - <p>If <c><anno>Dest</anno></c> is a <c>pid()</c>, the timer will be automatically - canceled if the process referred to by the <c>pid()</c> is not alive, - or when the process exits. This feature was introduced in - erts version 5.4.11. Note that timers will not be - automatically canceled when <c><anno>Dest</anno></c> is an <c>atom</c>.</p> - <p>See also - <seealso marker="#start_timer/3">erlang:start_timer/3</seealso>, - <seealso marker="#cancel_timer/1">erlang:cancel_timer/1</seealso>, - and - <seealso marker="#read_timer/1">erlang:read_timer/1</seealso>.</p> - <p>Failure: <c>badarg</c> if the arguments does not satisfy - the requirements specified above.</p> + <p>Starts a timer. The same as calling + <seealso marker="#send_after/4"><c>erlang:send_after(<anno>Time</anno>, + <anno>Dest</anno>, <anno>Msg</anno>, [])</c></seealso>.</p> </desc> </func> <func> @@ -5100,34 +5228,81 @@ true</pre> </desc> </func> <func> - <name name="start_timer" arity="3"/> - <type_desc variable="Time">0 <= Time <= 4294967295</type_desc> + <name name="start_timer" arity="4"/> <fsummary>Start a timer</fsummary> <desc> - <p>Starts a timer which will send the message - <c>{timeout, <anno>TimerRef</anno>, <anno>Msg</anno>}</c> to <c><anno>Dest</anno></c> - after <c><anno>Time</anno></c> milliseconds.</p> - <p>If <c><anno>Dest</anno></c> is a <c>pid()</c> it has to be a <c>pid()</c> of a local process, dead or alive.</p> - <p>The <c><anno>Time</anno></c> value can, in the current implementation, not be greater than 4294967295.</p> - <p>If <c><anno>Dest</anno></c> is an <c>atom()</c>, it is supposed to be the name of - a registered process. The process referred to by the name is - looked up at the time of delivery. No error is given if - the name does not refer to a process.</p> - <p>If <c><anno>Dest</anno></c> is a <c>pid()</c>, the timer will be automatically - canceled if the process referred to by the <c>pid()</c> is not alive, - or when the process exits. This feature was introduced in - erts version 5.4.11. Note that timers will not be - automatically canceled when <c><anno>Dest</anno></c> is an <c>atom()</c>.</p> + <p> + Starts a timer. When the timer expires, the message + <c>{timeout, <anno>TimerRef</anno>, <anno>Msg</anno>}</c> + will be sent to the process identified by + <c><anno>Dest</anno></c>. + </p> + <p>Currently available <c><anno>Option</anno></c>s:</p> + <taglist> + <tag><c>{abs, Abs}</c></tag> + <item> + <p> + Absolute <c><anno>Time</anno></c> value. <c>Abs</c> + defaults to <c>false</c> which means that the + <c><anno>Time</anno></c> value will be interpreted + as a time in milli-seconds relative current + <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang + monotonic time</seealso>. When <c>Abs</c> is set to + <c>true</c>, the <c><anno>Time</anno></c> value will + be interpreted as an absolute Erlang monotonic time of + milli-seconds + <seealso marker="#type_time_unit">time unit</seealso>. + </p> + </item> + </taglist> + <p> + More <c><anno>Option</anno></c>s may be added in the future. + </p> + <p> + The absolute point in time that the timer is set to expire on + has to be in the interval + <c>[</c><seealso marker="#system_info_start_time"><c>erlang:system_info(start_time)</c></seealso><c>, + </c><seealso marker="#system_info_end_time"><c>erlang:system_info(end_time)</c></seealso><c>]</c>. + Further, if a relative time is specified, the <c><anno>Time</anno></c> value + is not allowed to be negative. + </p> + <p> + If <c><anno>Dest</anno></c> is a <c>pid()</c>, it has to + be a <c>pid()</c> of a process created on the current + runtime system instance. This process may or may not + have terminated. If <c><anno>Dest</anno></c> is an + <c>atom()</c>, it will be interpreted as the name of a + locally registered process. The process referred to by the + name is looked up at the time of timer expiration. No error + is given if the name does not refer to a process. + </p> + <p> + If <c><anno>Dest</anno></c> is a <c>pid()</c>, the timer will + be automatically canceled if the process referred to by the + <c>pid()</c> is not alive, or when the process exits. This + feature was introduced in erts version 5.4.11. Note that + timers will not be automatically canceled when + <c><anno>Dest</anno></c> is an <c>atom()</c>. + </p> <p>See also - <seealso marker="#send_after/3">erlang:send_after/3</seealso>, - <seealso marker="#cancel_timer/1">erlang:cancel_timer/1</seealso>, + <seealso marker="#send_after/4"><c>erlang:send_after/4</c></seealso>, + <seealso marker="#cancel_timer/2"><c>erlang:cancel_timer/2</c></seealso>, and - <seealso marker="#read_timer/1">erlang:read_timer/1</seealso>.</p> + <seealso marker="#read_timer/2"><c>erlang:read_timer/2</c></seealso>.</p> <p>Failure: <c>badarg</c> if the arguments does not satisfy the requirements specified above.</p> </desc> </func> <func> + <name name="start_timer" arity="3"/> + <fsummary>Start a timer</fsummary> + <desc> + <p>Starts a timer. The same as calling + <seealso marker="#start_timer/4"><c>erlang:start_timer(<anno>Time</anno>, + <anno>Dest</anno>, <anno>Msg</anno>, [])</c></seealso>.</p> + </desc> + </func> + <func> <name name="statistics" arity="1" clause_i="1"/> <fsummary>Information about context switches</fsummary> <desc> @@ -6236,6 +6411,14 @@ ok (i.e. <c>system_info(dynamic_trace)</c> returns <c>dtrace</c> or <c>systemtap</c>).</p> </item> + <tag><marker id="system_info_end_time"/><c>end_time</c></tag> + <item><p>The last <seealso marker="#monotonic_time/0">Erlang monotonic + time</seealso> in <c>native</c> + <seealso marker="#type_time_unit">time unit</seealso> that + can be represented internally in the current Erlang runtime system + instance. The time between the + <seealso marker="#system_info_start_time">start time</seealso> and + the end time is at least a quarter of a millennium.</p></item> <tag><c>elib_malloc</c></tag> <item> <p>This option will be removed in a future release. @@ -6680,7 +6863,9 @@ ok <item><p>The <seealso marker="#monotonic_time/0">Erlang monotonic time</seealso> in <c>native</c> <seealso marker="#type_time_unit">time unit</seealso> at the - time when current Erlang runtime system instance started.</p></item> + time when current Erlang runtime system instance started. See also + <seealso marker="#system_info_end_time"><c>erlang:system_info(end_time)</c></seealso>. + </p></item> <tag><c>system_version</c></tag> <item> <p>Returns a string containing version number and |