timer_create
- create a per-process timer (REALTIME)
LIBRARY
Lb librt
SYNOPSIS
#include <time.h> int
Fo timer_create
Fa clockid_t clockid struct sigevent *restrict evp
Fa timer_t *restrict timerid
Fc
DESCRIPTION
The
timer_create ();
system call creates a per-process timer using the specified clock,
Fa clock_id ,
as the timing base.
The
timer_create ();
system call returns, in the location referenced by
Fa timerid ,
a timer ID of type
Vt timer_t
used to identify the timer in timer requests.
This timer ID is unique within the calling process until the timer is deleted.
The particular clock,
Fa clock_id ,
is defined in
In time.h .
The timer whose ID is returned is in a disarmed state upon return from
timer_create (.);
The
Fa evp
argument, if
non- NULL
points to a
Vt sigevent
structure.
This structure,
allocated by the application, defines the asynchronous notification to occur
when the timer expires.
If the
Fa evp
argument is
NULL
the effect is as if the
Fa evp
argument pointed to a
Vt sigevent
structure with the
sigev_notify
member having the value
SIGEV_SIGNAL
the
sigev_signo
having a default signal number, and the
sigev_value
member having
the value of the timer ID.
The implementations supports a
Fa clock_id
of
CLOCK_REALTIME
or
CLOCK_MONOTONIC
If
Fa evp->sigev_sigev_notify
is
SIGEV_THREAD
and
Fa sev->sigev_notify_attributes
is not
NULL
if the attribute pointed to by
Fa sev->sigev_notify_attributes
has
a thread stack address specified by a call to
pthread_attr_setstack ();
or
pthread_attr_setstackaddr (,);
the results are unspecified if the signal is generated more than once.
RETURN VALUES
If the call succeeds,
timer_create ();
returns zero and updates the location referenced by
Fa timerid
to a
Vt timer_t ,
which can be passed to the per-process timer calls.
If an error
occurs, the system call returns a value of -1
and the global variable
errno
is set to indicate the
error.
The value of
Fa timerid
is undefined if an error occurs.
ERRORS
The
timer_create ();
system call
will fail if:
Bq Er EAGAIN
The calling process has already created all of the timers it is allowed by
this implementation.
Bq Er EINVAL
The specified clock ID is not supported.
Bq Er EFAULT
Any arguments point outside the allocated address space or there is a
memory protection fault.
