getitimer(3C)                                                 getitimer(3C)

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

SYNOPSIS
     #include <sys/time.h>

     int getitimer(int which, struct itimerval *value);

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

DESCRIPTION
     The system provides each process with three interval timers, defined
     in sys/time.h. The getitimer() call stores the current value of the
     timer specified by which into the structure pointed to by value. The
     setitimer() call sets the value of the timer specified by which to the
     value specified in the structure pointed to by value, and if ovalue is
     not NULL, stores the previous value of the timer in the structure
     pointed to by ovalue.

     A timer value is defined by the itimerval structure (see
     gettimeofday(3C) for the definition of timeval), which includes the
     following members:

          struct timeval   itinterval;    /* timer interval */
          struct timeval   itvalue;       /* current value */

     If itvalue is non-zero, it indicates the time to the next timer
     expiration. If itinterval is non-zero, it specifies a value to be
     used in reloading itvalue when the timer expires. Setting itvalue to
     zero disables a timer, regardless of the value of itinterval. Setting
     itinterval to zero disables a timer after its next expiration (assum-
     ing itvalue is non-zero).

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

     The three timers are:

     ITIMERREAL    Decrements in real time. A SIGALRM signal is delivered
                    when this timer expires.

     ITIMERVIRTUAL Decrements in process virtual time (user mode). It runs
                    only when the process is executing. A SIGVTALRM signal
                    is delivered when it expires.










Page 1                       Reliant UNIX 5.44                Printed 11/98

getitimer(3C)                                                 getitimer(3C)

     ITIMERPROF    Decrements both in process virtual time and when the
                    system is running on behalf of the process (user and
                    system mode). It is designed to be used by interpreters
                    in statistically profiling the execution of interpreted
                    programs. Each time the ITIMERPROF 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.

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

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

     Under the following conditions, the functions getitimer() and
     setitimer() fail and set errno to:

     EINVAL   The specified number of seconds is greater than 100,000,000,
              the number of microseconds is greater than or equal to
              1,000,000, or the which parameter is unrecognized.

NOTES
     The microseconds field should not be equal to or greater than one
     second.

     setitimer() is independent of the alarm system call.

     Do not use setitimer() with the sleep routine. A sleep following a
     setitimer() wipes out knowledge of the user signal handler.

SEE ALSO
     alarm(2), usleep(3), gettimeofday(3C), sleep(3C), sleep(3C-ucb), sig-
     nal(5), systime(5), time(5).

















Page 2                       Reliant UNIX 5.44                Printed 11/98