timer_create(3) Library Functions Manual timer_create(3)
NAME
timer_create - Allocates a per-process timer
LIBRARY
Realtime Library (librt.so, librt.a)
SYNOPSIS
#include <signal.h> #include <time.h>
int timer_create ( clockid_t clock_id, struct sigevent *evp, timer_t *timerid );
PARAMETERS
clock_id The type of clock on which the timer is based. The CLOCK_REALTIME clock is supported.
*evp A pointer to a sigevent structure, which defines the signal sent to the process on timer expiration.
*timerid A pointer to the timer ID returned by the call to the timer_create function.
DESCRIPTION
The timer_create function allocates a per-process timer using the specified clock as the timing base. The timer_create function returns
timer_id, which identifies the timer in timer requests. The timer ID is unique within the calling process until the timer is deleted. The
timer is unarmed when first returned from a call to timer_create. To arm the timer, use the timer_settime function.
The evp argument, if non-NULL, points to a sigevent structure, which defines the asynchronous notification that occurs when the timer
expires. If the sigev_notify member of evp is SIGEV_SIGNAL, the structure must contain the signal number and data value to send to the
process when the timer expires. If the sigev_notify member is SIGEV_NONE, no notification is sent.
SIGALRM is the default signal for CLOCK_REALTIME if the evp argument is NULL.
The maximum number of timers supported per process (TIMER_MAX) is defined in the <sys/rt_limits.h> header file, which is indirectly
included through <time.h>.
Timers are not inherited across fork calls. An exec call disarms and deletes a timer.
RETURN VALUES
Upon successful completion, a value of 0 (zero) is returned. The timer_create function also returns, in timerid, a pointer to the timer ID
that has been created.
An unsuccessful call returns -1, and errno is set to indicate the error type.
ERRORS
The timer_create function fails under the following conditions:
[EAGAIN] The system lacks sufficient signal queuing resources to honor the request.
The calling process has already created all of the timers it is allowed.
[EINVAL] The specified clock ID is not defined.
RELATED INFORMATION
Functions: clock_getres(3), clock_gettime(3), clock_settime(3), timer_delete(3), timer_gettime(3), timer_settime(3)
Guide to Realtime Programming delim off
timer_create(3)
