timers.2 (2010 09)

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timers(2) timers(2)

If the ﬂag TIMER_ABSTIME

is set in the argument ﬂags,

timer_settime() behaves as if the time

until next expiration is set equal to the difference between the absolute time speciﬁed by the it_value

member of value and the current value of the clock associated with timerid . That is, the timer will expire

when the clock reaches the value speciﬁed by the it_value member of value . If the speciﬁed time has

already passed, the function will succeed and the expiration notiﬁcation is made.

The reload value of the timer is set to the value speciﬁed by the it_interval member of value . When a

timer is armed with a non-zero it_interval , a periodic (or repetitive) timer is speciﬁed.

Time values that are between two consecutive non-negative integer multiples of the resolution of the

speciﬁed timer are rounded up to the larger multiple of the resolution. A quantization error will not

cause the timer to expire earlier than the rounded-up time value.

If the argument ovalue is not NULL, the function

timer_settime() stores, in the location referenced

by ovalue , a value representing the previous amount of time before the timer would have expired or zero

if the timer was disarmed, together with the previous timer reload value. The members of ovalue are

subject to the resolution of the timer, and are the same values that would be returned by a

timer_gettime()

call at that point in time.

timer_gettime()

The

timer_gettime()

function stores the amount of time until the speciﬁed timer, timerid ,expires

and the timer’s reload value into the space pointed to by the value argument. The it_value member of

this structure will contain the amount of time before the timer expires, or zero if the timer is disarmed.

This value is returned as the interval until timer expiration, even if the timer was armed with absolute

time. The it_interval member of value will contain the reload value last set by

timer_settime()

timer_getoverrun()

Only a single signal is delivered to the process for a given timer at any point in time. When a timer for

which a signal is still pending expires, no signal is delivered, and a timer overrun has occurred. When a

timer expiration signal is delivered to a process, the

timer_getoverrun()

function returns the timer

expiration count for the speciﬁed timer. The overrun count returned contains the number of extra timer

expirations which occurred between the time the signal was generated and when it was delivered, up to

but not including an implementation deﬁned maximum of

DELAYTIMER_MAX. If the number of such

extra expirations is greater than or equal to

DELAYTIMER_MAX

, then the overrun count is set to

DELAYTIMER_MAX. The value returned by

timer_getoverrun() applies to the most recent expira-

tion signal delivery for the timer. If no expiration signal has been delivered for the timer, the meaning of

the overrun count returned is undeﬁned.

RETURN VALUE

Upon successful completion,

timer_create()

returns zero and updates the location referenced by

timerid to a timer_t which can be passed to the per-process timer calls. Otherwise,

timer_create()

returns − 1 and sets errno to indicate the error. The value of timerid is undeﬁned if an error occurs.

Upon successful completion,

timer_delete()

returns zero. Otherwise, timer_delete() returns

−1 and sets

errno to indicate the error.

Upon successful completion,

timer_settime() returns zero and updates the location referenced by

ovalue ,ifovalue is non-NULL.

Upon successful completion,

timer_gettime() returns zero and updates the location referenced by

value ,ifovalue is non-NULL. Otherwise, timer_gettime() returns −1 and sets errno to indicate

the error.

Upon successful completion,

timer_getoverrun() returns the timer expiration overrun count as

explained above. Otherwise, timer_getoverrun() returns −1 and sets errno to indicate the error.

ERRORS

If any of the following conditions occur, the

timer_create() function returns −1 and sets errno (see

errno(2)) to the corresponding value:

[EAGAIN] The system lacks sufﬁcient signal queuing resources to honor the request.

[EAGAIN] The calling process has already created all of the timers it is allowed by this implemen-

tation.

[EINVAL] The speciﬁed clock ID is not deﬁned.

2 Hewlett-Packard Company − 2 − HP-UX 11i Version 3: September 2010