Description

   The setitimer function sets the timer specified by which to the
   value specified by value, returning the previous value of the
   timer if ovalue is nonzero.

   A timer value is defined by the itimerval structure:

          struct itimerval {
                  struct  timeval it_interval;
                  struct  timeval it_value;
          };

   The value of the itimerval structure members are: as follows

   itimerval Member
   Value              Meaning

   it_interval = 0    Disables a timer after its next expiration
                      (assumes it_value is nonzero).
   it_interval =      Specifies a value used in reloading it_value
   nonzero            when the timer expires.
   it_value = 0       Disables a timer.
   it_value =         Indicates the time to the next timer
   nonzero            expiration.

   Time values smaller than the resolution of the system clock are
   rounded up to this resolution.

   The getitimer function provides one interval timer, defined in
   the <time.h> header file as ITIMER_REAL. This timer decrements in
   real time. When the timer expires, it delivers a SIGALARM signal.

                                  NOTE

      The interaction between setitimer and any of alarm, sleep,
      or usleep is unspecified.