Manual Pages for UNIX Operating System command usage for man gethrvtime

Standard C Library Functions                        gethrtime(3C)



NAME
     gethrtime, gethrvtime - get high resolution time

SYNOPSIS
     #include 

     hrtime_t gethrtime(void);


     hrtime_t gethrvtime(void);


DESCRIPTION
     The gethrtime() function returns the current high-resolution
     real time. Time is expressed as nanoseconds since some arbi-
     trary time in the past; it is not correlated in any  way  to
     the  time  of  day,  and thus is not subject to resetting or
     drifting by way of adjtime(2) or settimeofday(3C).  The  hi-
     res  timer  is  ideally  suited  to  performance measurement
     tasks, where cheap, accurate interval timing is required.


     The  gethrvtime()  function  returns   the   current   high-
     resolution  LWP virtual time, expressed as total nanoseconds
     of execution time.


     The gethrtime() and gethrvtime() functions  both  return  an
     hrtime_t, which is a 64-bit (long long) signed integer.

EXAMPLES
     The following code fragment measures  the  average  cost  of
     getpid(2):

       hrtime_t start, end;
       int i, iters = 100;

       start = gethrtime();
       for (i = 0; i < iters; i++)
               getpid();
       end = gethrtime();

       printf("Avg getpid() time = %lld nsec\n", (end - start) / iters);


ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:







SunOS 5.11           Last change: 7 Sep 2004                    1






Standard C Library Functions                        gethrtime(3C)



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|


SEE ALSO
     proc(1),  adjtime(2),  gettimeofday(3C),   settimeofday(3C),
     attributes(5)

NOTES
     Although the units  of  hi-res  time  are  always  the  same
     (nanoseconds),  the actual resolution is hardware dependent.
     Hi-res time is guaranteed to be monotonic (it won't go back-
     ward, it won't periodically wrap) and linear (it won't occa-
     sionally speed up or slow down for adjustment, like the time
     of  day  can),  but not necessarily unique: two sufficiently
     proximate calls may return the same value.




































SunOS 5.11           Last change: 7 Sep 2004                    2