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Linux 2.6 - man page for setitimer (linux section 3posix)

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

       getitimer, setitimer - get and set value of interval timer

       #include <sys/time.h>

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

       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 spec-
       ified  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 structure  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. Setting 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 values. For each  inter-
       val  timer, if the requested timer value requires a finer granularity than the implementa-
       tion 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:

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

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

	      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 interpreted 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 unspeci-

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

       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.





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

       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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003				     GETITIMER(P)

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