Man Page Of gethrtime

Man Page Of gethrtime

题注:Man Page这里我辑录一些我在学习研究过程中关注过，应用过的，供自己参考，也希望可以见证自己的学习历程。

$ man gethrtimeStandard C Library Functions gethrtime(3C)NAME gethrtime, gethrvtime - get high resolution timeSYNOPSIS #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 arbitrary 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 hires 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. This function requires that micro state accounting be enabled with the ptime utility (see proc(1)). 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\", (end - start) / iters);ATTRIBUTES See attributes(5) for descriptions of the following attributes: ____________________________________________________________ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | |_____________________________|_____________________________| | MT-Level | MT-Safe | |_____________________________|_____________________________|SunOS 5.8 Last change: 10 Apr 1997 1Standard C Library Functions gethrtime(3C)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 backward, it won't periodically wrap) and linear (it won't occasionally 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 5.8 Last change: 10 Apr 1997 2