[apple/xnu.git] / osfmk / man / clock_alarm.html

<h2>clock_alarm</h2>\r<hr>\r<p>\r<strong>Function</strong> - Set off an alarm.\r<h3>SYNOPSIS</h3>\r<pre>\r<strong>kern_return_t   clock_alarm</strong>\r                <strong>(clock_t</strong>                             <var>clock_name</var>,\r                 <strong>alarm_type_t</strong>                        <var>alarm_type</var>,\r                 <strong>tvalspec_t</strong>                          <var>alarm_time</var>,\r                 <strong>mach_port_t</strong>                   <var>alarm_reply_port</var><strong>);</strong>\r</pre>\r<h3>PARAMETERS</h3>\r<dl>\r<p>\r<dt> <var>clock_name</var> \r<dd>\r[in clock-name send right]\rThe name (or control) port for the clock.\r<p>\r<dt> <var>alarm_type</var> \r<dd>\r[in scalar]\rHow to interpret the <var>alarm_time</var> value:\r<dl>\r<p>\r<dt> <strong>TIME_RELATIVE</strong>\r<dd>\rInterpret the alarm time as relative to the current time.\r<p>\r<dt> <strong>TIME_ABSOLUTE</strong>\r<dd>\rInterpret the alarm time as an absolute time.\r</dl>\r<p>\r<dt> <var>alarm_time</var> \r<dd>\r[in structure]\rThe time when the alarm is to be sent.\r<p>\r<dt> <var>alarm_reply_port</var> \r<dd>\r[in alarm receive (to be converted to send-once) right]\rA port into \rwhich the alarm message is to be sent.\r</dl>\r<h3>DESCRIPTION</h3>\r<p>\rThe <strong>clock_alarm</strong> function requests that a clock send\ran alarm message to a \rspecified port at a given future time.  The alarm message is specified by the \r<strong>clock_alarm_reply</strong> server interface.\r<h3>NOTES</h3>\r<p>\rIf the specified alarm time is in the past, the alarm message\ris sent immediately \rand time-stamped with the current time.  Otherwise, the alarm is queued and\rdelivered at the specified alarm time and time-stamped at that time.\r<p>\rThe alarm will be serviced at the service time nearest the specified\ralarm time \ras governed by the current clock alarm resolution.\r<p>\rNot all clocks implement this service, but the REALTIME clock must.  If the \rclock does not provide this service, this call is ignored.\r<h3>RETURN VALUES</h3>\r<p>\rOnly generic errors apply.\r<h3>RELATED INFORMATION</h3>\r<p>\rFunctions:\r<a href="host_get_clock_service.html"><strong>host_get_clock_service</strong></a>,\r<a href="clock_get_attributes.html"><strong>clock_get_attributes</strong></a>,\r<a href="clock_get_time.html"><strong>clock_get_time</strong></a>,\r<a href="clock_sleep.html"><strong>clock_sleep</strong></a>,\r<a href="clock_alarm_reply.html"><strong>clock_alarm_reply</strong></a>.\r<p>\rData Structures:\r<a href="tvalspec.html"><strong>tvalspec</strong></a>.\r