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memorylost731

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linux_man_pages_library

like 1

argument.

.pp

the

.i flags

argument is a bit mask that can include the following values:

.tp

.b tfd_timer_abstime

interpret

.i new_value.it_value

as an absolute value on the timer's clock.

the timer will expire when the value of the timer's

clock reaches the value specified in

.ir new_value.it_value .

.tp

.br tfd_timer_cancel_on_set

if this flag is specified along with

.b tfd_timer_abstime

and the clock for this timer is

.br clock_realtime

or

.br clock_realtime_alarm ,

then mark this timer as cancelable if the real-time clock

undergoes a discontinuous change

.rb ( settimeofday (2),

.br clock_settime (2),

or similar).

when such changes occur, a current or future

.br read (2)

from the file descriptor will fail with the error

.br ecanceled .

.pp

if the

.i old_value

argument is not null, then the

.i itimerspec

structure that it points to is used to return the setting of the timer

that was current at the time of the call;

see the description of

.br timerfd_gettime ()

following.

.\"

.ss timerfd_gettime()

.br timerfd_gettime ()

returns, in

.ir curr_value ,

an

.ir itimerspec

structure that contains the current setting of the timer

referred to by the file descriptor

.ir fd .

.pp

the

.i it_value

field returns the amount of time

until the timer will next expire.

if both fields of this structure are zero,

then the timer is currently disarmed.

this field always contains a relative value, regardless of whether the

.br tfd_timer_abstime

flag was specified when setting the timer.

.pp

the

.i it_interval

field returns the interval of the timer.

if both fields of this structure are zero,

then the timer is set to expire just once, at the time specified by

.ir curr_value.it_value .

.ss operating on a timer file descriptor

the file descriptor returned by

.br timerfd_create ()

supports the following additional operations:

.tp

.br read (2)

if the timer has already expired one or more times since

its settings were last modified using

.br timerfd_settime (),

or since the last successful

.br read (2),

then the buffer given to

.br read (2)

returns an unsigned 8-byte integer

.ri ( uint64_t )

containing the number of expirations that have occurred.

(the returned value is in host byte order\(emthat is,

the native byte order for integers on the host machine.)

.ip

if no timer expirations have occurred at the time of the

.br read (2),

then the call either blocks until the next timer expiration,

or fails with the error

.b eagain

if the file descriptor has been made nonblocking

(via the use of the

.br fcntl (2)

.b f_setfl

operation to set the

.b o_nonblock

flag).

.ip

a