TIMER_SETTIME(2) BSD System Calls Manual TIMER_SETTIME(2)NAME
timer_settime, timer_gettime, timer_getoverrun — process timer manipula‐
tion
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <time.h>
int
timer_settime(timer_t timerid, int flags,
const struct itimerspec * restrict tim,
struct itimerspec * restrict otim);
int
timer_gettime(timer_t timerid, struct itimerspec *tim);
int
timer_getoverrun(timer_t timerid);
DESCRIPTION
The timer_settime() sets the next expiration time of the timer with ID
timerid to the it_value (see itimerspec(3)) specified in the tim argu‐
ment. If the value is 0, the timer is disarmed. If the argument otim is
not NULL the old timer settingas are returned.
If the flags argument is set to TIMER_RELTIME then the expiration time is
set to the value in nanoseconds specified in the tim argument from the
time the call to timer_settime() was made. If the flags argument is set
to TIMER_ABSTIME then the expiration time is set to be equal to the dif‐
ference between the clock associated with this timer, and the value spec‐
ified in the tim argument. If that time has already passed, then the
call succeeds, and the expiration notification occurs.
If the it_interval of the tim argument is non-zero, then the timer
reloads upon expiration.
The timer_gettime() function returns the current settings of the timer
specified by the timerid argument in the tim argument.
Only one notification event (signal) can be pending for a given timer and
process. If a timer expires while the signal is still queued for deliv‐
ery, then the overrun counter for that timer is increased. The counter
can store values up to DELAYTIMER_MAX. When the signal is finally deliv‐
ered to the process, then the timer_getoverrun() function can be used to
retrieve the overrun counter for the timer specified in the timerid argu‐
ment.
NOTES
Expiration time values are always rounded up to the resolution of the
timer, so a notification will never be sent before the requested time.
Values returned in the otim argument of timer_settime() or in the tim
argment of timer_gettime() are subject to the above rounding effect and
might not exactly match the requested values by the user.
RETURN VALUES
If successful, the timer_gettime() and timer_settime() functions return
0, and the timer_getoverrun() function returns the expiration overrun
count for the specified timer. Otherwise, the functions return -1, and
set errno to indicate the error.
ERRORS
The timer_gettime(), timer_getoverrun(), and timer_settime() functions
will fail if:
[EINVAL] The argument timerid does not correspond to a valid
timer id as returned by timer_create() or that timer
id has been deleted by timer_delete().
The timer_settime() function will fail if:
[EINVAL] A nanosecond field in the tim structure specified a
value less than zero or greater than or equal to 10e9.
SEE ALSOclock_gettime(2), timer_create(2), timer_delete(2)STANDARDS
IEEE Std 1003.1b-1993 (“POSIX.1”), IEEE Std 1003.1i-1995 (“POSIX.1”)
BSD May 17, 2010 BSD
