getitimer, setitimer

Purpose

     Gets and sets value of internal timer.

Library

     Berkeley Library (libbsd.a)

Syntax

     #include <bsd/sys/time.h>

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

     The getitimer subroutine returns the current value of the
     timer specified in which.   The setitimer subroutine sets
     the timer in which to  the specified value, returning the
     previous value of the timer if ovalue is not 0.

     The  itimerval structure  describes the  timer value,  as
     defined in  the bsd/sys/time.h  header file, and  it con-
     tains the following members:

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

     Setting  it_interval to  0  disables the  timer after  it
     expires.  An  it_interval other than 0  specifies a value
     used to reload it_value when the timer expires.

     The it_value  disables the timer immediately  when set to
     0.  An  it_value other than  0 indicates the time  of the
     next timer expiration.

     Time  values smaller  than the  resolution of  the system
     clock  are rounded  up  to its  resolution,  1/60th of  a
     second.

     The ITIMER_REAL  timer decrements in real  time.  When it
     expires,  the system  delivers a  SIGALRM signal.   Timer
     values ITIMER_VIRTUAL and ITIMER_PROF are not supported.

     Return Value

     Upon  successful completion,  a value  of 0  is returned.
     Otherwise, a value of -1 is returned, and errno is set to
     indicate the error.

     Diagnostics

     The  getitimer or  setitimer subroutine  fails if  one or
     more of the following is true:

     EFAULT     The value or ovalue parameter &pointsout..

     EINVAL     The value parameter specifies a time too large
                to handle.

     EINVAL     The  which  parameter   specifies  an  illegal
                value.

     Related Information

     In this book:  "gettimeofday" and "sigvec."