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GETITIMER(P)		   POSIX Programmer's Manual		  GETITIMER(P)

NAME
       getitimer, setitimer - get and set value of interval timer

SYNOPSIS
       #include <sys/time.h>

       int getitimer(int which, struct itimerval *value);
       int setitimer(int which, const struct itimerval *restrict value,
	      struct itimerval *restrict ovalue);

DESCRIPTION
       The  getitimer()	 function  shall  store the current value of the timer
       specified by  which  into  the  structure  pointed  to  by  value.  The
       setitimer()  function  shall  set  the  timer specified by which to the
       value specified in the structure pointed to by value, and if ovalue  is
       not a null pointer, store the previous value of the timer in the struc‐
       ture pointed to by ovalue.

       A timer value is defined	 by  the  itimerval  structure,	 specified  in
       <sys/time.h>.  If  it_value  is non-zero, it shall indicate the time to
       the next timer expiration. If it_interval is non-zero, it shall specify
       a  value	 to be used in reloading it_value when the timer expires. Set‐
       ting it_value to 0 shall disable a timer, regardless of	the  value  of
       it_interval.  Setting  it_interval to 0 shall disable a timer after its
       next expiration (assuming it_value is non-zero).

       Implementations may place limitations on the granularity of timer  val‐
       ues.  For  each interval timer, if the requested timer value requires a
       finer granularity than the implementation supports,  the	 actual	 timer
       value shall be rounded up to the next supported value.

       An  XSI-conforming  implementation  provides each process with at least
       three interval timers, which are indicated by the which argument:

       ITIMER_REAL
	      Decrements in real time. A SIGALRM signal is delivered when this
	      timer expires.

       ITIMER_VIRTUAL
	      Decrements  in  process  virtual	time.  It  runs	 only when the
	      process is executing. A SIGVTALRM signal is  delivered  when  it
	      expires.

       ITIMER_PROF
	      Decrements  both	in process virtual time and when the system is
	      running on behalf of the process. It is designed to be  used  by
	      interpreters  in statistically profiling the execution of inter‐
	      preted programs. Each time the ITIMER_PROF  timer	 expires,  the
	      SIGPROF signal is delivered.

       The  interaction	 between  setitimer()  and any of alarm(), sleep(), or
       usleep() is unspecified.

RETURN VALUE
       Upon successful completion, getitimer() or setitimer() shall return  0;
       otherwise, -1 shall be returned and errno set to indicate the error.

ERRORS
       The setitimer() function shall fail if:

       EINVAL The value argument is not in canonical form. (In canonical form,
	      the number of microseconds is a non-negative integer  less  than
	      1000000 and the number of seconds is a non-negative integer.)

       The getitimer() and setitimer() functions may fail if:

       EINVAL The which argument is not recognized.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       alarm() , sleep() , timer_getoverrun() , ualarm() , usleep() , the Base
       Definitions volume of IEEE Std 1003.1-2001, <signal.h>, <sys/time.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),	The  Open  Group  Base
       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard
       is  the	referee document. The original Standard can be obtained online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group		     2003			  GETITIMER(P)
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