GETITIMER(2)              NetBSD System Calls Manual              GETITIMER(2)

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

LIBRARY
     Standard C Library (libc, -lc)

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 system provides each process with three interval timers, defined in
     <sys/time.h>.  The getitimer() call returns the current value for the
     timer specified in which in the structure at value.  The setitimer() call
     sets a timer to the specified value, returning the previous value of the
     timer if ovalue is not NULL.

     A timer value is defined by the itimerval structure:

           struct itimerval {
                   struct  timeval it_interval;    /* timer interval */
                   struct  timeval it_value;       /* current value */
           };

     If it_value is non-zero, it indicates the time to the next timer expira-
     tion.  If it_interval is non-zero, it specifies a value to be used in
     reloading it_value when the timer expires.  Setting it_value to 0 dis-
     ables a timer.  Setting it_interval to 0 causes a timer to be disabled
     after its next expiration (assuming it_value is non-zero).

     The which parameter specifies the type of the timer:

           ITIMER_REAL        timer decrements in real time.  This timer is
                              affected by adjtime(2) and settimeofday(2).  A
                              SIGALRM signal is delivered when this timer
                              expires.

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

           ITIMER_PROF        timer 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 signal is
                              delivered.  Because this signal may interrupt
                              in-progress system calls, programs using this
                              timer must be prepared to restart interrupted
                              system calls.

           ITIMER_MONOTONIC   timer decrements in monotonic time.  This timer
                              is not affected by adjtime(2) and
                              settimeofday(2).  A SIGALRM signal is delivered
                              when this timer expires.
     Note that:

              Time values smaller than the resolution of the system clock are
               rounded up to this resolution (typically 10 milliseconds).

              The interaction between setitimer() and alarm(3) or sleep(3) is
               unspecified by the specification.

RETURN VALUES
     If the calls succeed, a value of 0 is returned.  If an error occurs, the
     value -1 is returned, and a more precise error code is placed in the
     global variable errno.

ERRORS
     Both functions may fail if:

     [EFAULT]           The value parameter specified a bad address.

     [EINVAL]           The which parameter was not a known timer type, or the
                        value parameter specified a time that was too large to
                        be handled.

SEE ALSO
     gettimeofday(2), select(2), sigaction(2), itimerval(3), timeradd(3)

STANDARDS
     The functions conform to IEEE Std 1003.1-2001 (``POSIX.1'').  The later
     IEEE Std 1003.1-2008 (``POSIX.1'') revision however marked both as obso-
     lescent, recommending the use of timer_gettime(2) and timer_settime(2)
     instead.

HISTORY
     The getitimer() function call appeared in 4.2BSD.  The ITIMER_MONOTONIC
     functionality appeared in NetBSD 6.0.

NetBSD 7.0                     October 27, 2011                     NetBSD 7.0

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