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 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.  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 values. 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 inter-
	      preters in statistically profiling the execution of interpreted programs. Each time the ITIMER_PROF timer expires, the SIGPROF  sig-
	      nal 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 Technol-
       ogy -- 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)