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All Rights Reserved. .\" Copyright (c) 2008, Sun Microsystems, Inc. All Rights Reserved. .\" .TH TIMER_CREATE 3C "Oct 04, 2021" .SH NAME timer_create \- create a timer .SH SYNOPSIS .nf #include #include \fBint\fR \fBtimer_create\fR(\fBclockid_t\fR \fIclock_id\fR, \fBstruct sigevent *restrict\fR \fIevp\fR, \fBtimer_t *restrict\fR \fItimerid\fR); .fi .SH DESCRIPTION The \fBtimer_create()\fR function creates a timer using the specified clock, \fIclock_id\fR, as the timing base. The \fBtimer_create()\fR function returns, in the location referenced by \fItimerid\fR, a timer \fBID\fR of type \fBtimer_t\fR used to identify the timer in timer requests. This timer \fBID\fR will be unique within the calling process until the timer is deleted. The particular clock, \fIclock_id\fR, is defined in <\fBtime.h\fR>. The timer whose \fBID\fR is returned will be in a disarmed state upon return from \fBtimer_create()\fR, and can be started using \fBtimer_settime\fR(3C). .LP The \fIevp\fR argument, if non-null, points to a \fBsigevent\fR structure. This structure, allocated by the application, defines the asynchronous notification that will occur when the timer expires (see \fBsignal.h\fR(3HEAD) for event notification details). If the \fIevp\fR argument is \fINULL\fR, the effect is as if the \fIevp\fR argument pointed to a \fBsigevent\fR structure with the \fBsigev_notify\fR member having the value \fBSIGEV_SIGNAL\fR, the \fBsigev_signo\fR having the value \fBSIGALRM\fR, and the \fBsigev_value\fR member having the value of the timer \fBID\fR. .LP The system defines a set of clocks that can be used as timing bases for per-process timers. The following values for \fIclock_id\fR are supported: .sp .ne 2 .na \fB\fBCLOCK_REALTIME\fR\fR .ad .RS 18n wall clock .RE .sp .ne 2 .na \fB\fBCLOCK_HIGHRES\fR\fR .ad .RS 18n non-adjustable, high-resolution clock .RE .sp .LP For timers created with a \fIclock_id\fR of \fBCLOCK_HIGHRES\fR, the system will attempt to use an optimal hardware source. This may include, but is not limited to, per-CPU timer sources. The actual hardware source used is transparent to the user and may change over the lifetime of the timer. For example, if the caller that created the timer were to change its processor binding or its processor set, the system may elect to drive the timer with a hardware source that better reflects the new binding. Timers based on a \fIclock_id\fR of \fBCLOCK_HIGHRES\fR are ideally suited for interval timers that have minimal jitter tolerance. .LP Timers are not inherited by a child process across a \fBfork\fR(2) and are disarmed and deleted by a call to one of the \fBexec\fR functions (see \fBexec\fR(2)). .SH RETURN VALUES Upon successful completion, \fBtimer_create()\fR returns \fB0\fR and updates the location referenced by \fItimerid\fR to a \fBtimer_t\fR, which can be passed to the per-process timer calls. If an error occurs, the function returns \fB\(mi1\fR and sets \fBerrno\fR to indicate the error. The value of \fItimerid\fR is undefined if an error occurs. .SH ERRORS The \fBtimer_create()\fR function will fail if: .sp .ne 2 .na \fB\fBEAGAIN\fR\fR .ad .RS 10n The system lacks sufficient signal queuing resources to honor the request, or the calling process has already created all of the timers it is allowed by the system. .RE .sp .ne 2 .na \fB\fBEINVAL\fR\fR .ad .RS 10n The specified clock \fBID\fR, \fIclock_id\fR, is not defined. .RE .SH ATTRIBUTES See \fBattributes\fR(7) for descriptions of the following attributes: .sp .sp .TS box; l | l l | l . ATTRIBUTE TYPE ATTRIBUTE VALUE _ Interface Stability Committed _ MT-Level MT-Safe with exceptions _ Standard See \fBstandards\fR(7). .TE .SH SEE ALSO .BR exec (2), .BR fork (2), .BR time (2), .BR clock_settime (3C), .BR signal (3C), .BR timer_delete (3C), .BR timer_settime (3C), .BR signal.h (3HEAD), .BR attributes (7), .BR standards (7)