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OpenSolaris 2009.06 - man page for setitimer (opensolaris section 2)

getitimer(2)				   System Calls 			     getitimer(2)

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

SYNOPSIS
       #include <sys/time.h>

       int getitimer(int which, struct itimerval *value);

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

DESCRIPTION
       The  system  provides each process with four interval timers, defined in <sys/time.h>. The
       getitimer() function stores the current value of the timer specified  by  which	into  the
       structure  pointed  to by value. The setitimer() function call sets the value of the timer
       specified by which to the value specified in the structure pointed to  by  value,  and  if
       ovalue  is not NULL, stores the previous value of the timer in the structure pointed to by
       ovalue.

       A timer value is defined by the itimerval structure (see gettimeofday(3C)) for the defini-
       tion of timeval), which includes the following members:

	 struct timeval    it_interval; 	/* timer interval */
	 struct timeval    it_value;		/* current value */

       The  it_value member indicates the time to the next timer expiration. The it_interval mem-
       ber specifies a value to be used in reloading it_value when  the  timer	expires.  Setting
       it_value  to 0 disables a timer, regardless of the value of it_interval. Setting it_inter-
       val to 0 disables a timer after its next expiration (assuming it_value is non-zero).

       Time values smaller than the resolution of the system clock are rounded up to the  resolu-
       tion  of the system clock, except for  ITIMER_REALPROF, whose values are rounded up to the
       resolution of the profiling clock. The four timers are as follows:

       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  interpreted  programs.  Each
			  time	the  ITIMER_PROF  timer expires, the SIGPROF signal is delivered.
			  Because this signal may interrupt in-progress functions, programs using
			  this timer must be prepared to restart interrupted functions.

       ITIMER_REALPROF	  Decrements  in  real time. It is designed to be used for real-time pro-
			  filing of multithreaded programs. Each time the  ITIMER_REALPROF  timer
			  expires,  one counter in a set of counters maintained by the system for
			  each lightweight process (lwp) is incremented. The counter  corresponds
			  to the state of the lwp at the time of the timer tick. All lwps execut-
			  ing in user mode when the timer expires  are	interrupted  into  system
			  mode.  When each lwp resumes execution in user mode, if any of the ele-
			  ments in its set of counters are non-zero, the SIGPROF signal is deliv-
			  ered	to the lwp. The SIGPROF signal is delivered before any other sig-
			  nal except SIGKILL. This signal  does  not  interrupt  any  in-progress
			  function.  A	siginfo structure, defined in <sys/siginfo.h>, is associ-
			  ated with the delivery of the SIGPROF signal, and includes the  follow-
			  ing members:

			    si_tstamp;	    /* high resolution timestamp */
			    si_syscall;     /* current syscall */
			    si_nsysarg;     /* number of syscall arguments */
			    si_sysarg[];     /* actual syscall arguments */
			    si_fault;	    /* last fault type */
			    si_faddr;	    /* last fault address */
			    si_mstate[];     /* ticks in each microstate */

			  The  enumeration of microstates (indices into  si_mstate) is defined in
			  <sys/msacct.h>.

RETURN VALUES
       Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is  set  to
       indicate the error.

ERRORS
       The getitimer() and setitimer() functions will fail if:

       EINVAL	 The  specified  number  of  seconds  is  greater than 100,000,000, the number of
		 microseconds is greater than or equal to 1,000,000, or  the  which  argument  is
		 unrecognized.

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO
       alarm(2), gettimeofday(3C), sleep(3C), sysconf(3C), attributes(5), standards(5)

NOTES
       The microseconds field should not be equal to or greater than one second.

       The setitimer() function is independent of the alarm() function.

       Do  not	use  setitimer(ITIMER_REAL)  with the sleep() routine. A sleep(3C) call wipes out
       knowledge of the user signal handler for SIGALRM.

       The ITIMER_PROF and ITIMER_REALPROF timers deliver the  same  signal  and  have	different
       semantics. They cannot be used together.

       The granularity of the resolution of alarm time is platform-dependent.

SunOS 5.11				    6 Jun 2001				     getitimer(2)


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