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.  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.
     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]           A 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.

NetBSD 5.0                        May 2, 2011                       NetBSD 5.0