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TIME(9) Kernel Developer's Manual TIME(9) NAME boottime, time_second, time_uptime -- system time variables SYNOPSIS #include <sys/time.h> extern struct timeval boottime; extern time_t time_second; extern time_t time_uptime; DESCRIPTION The boottime variable holds the estimated system boot time. This time is initially set when the system boots, either from the RTC, or from a time estimated from the system's root filesystem. When the current system time is set, stepped by ntpd(8), or a new time is read from the RTC as the sys- tem resumes, boottime is recomputed as new_time - uptime. The sysctl(8) kern.boottime returns this value. The time_second variable is the system's "wall time" clock to the second. The time_uptime variable is the number of seconds since boot. The bintime(9), getbintime(9), microtime(9), getmicrotime(9), nanotime(9), and getnanotime(9) functions can be used to get the current time more accu- rately and in an atomic manner. Similarly, the binuptime(9), getbinup- time(9), microuptime(9), getmicrouptime(9), nanouptime(9), and getnanoup- time(9) functions can be used to get the time elapse since boot more accu- rately and in an atomic manner. The boottime variable may be read and written without special precautions. It is adjusted when the phase of the system time changes. SEE ALSO clock_settime(2), ntp_adjtime(2), settimeofday(2), bintime(9), binup- time(9), getbintime(9), getbinuptime(9), getmicrotime(9), getmicroup- time(9), getnanotime(9), getnanouptime(9), microtime(9), microuptime(9), nanotime(9), nanouptime(9) Poul-Henning Kamp, "Timecounters: Efficient and precise timekeeping in SMP kernels", Proceedings of EuroBSDCon 2002, Amsterdam, /usr/share/doc/pa- pers/timecounter.ascii.gz. Marshall Kirk McKusick and George V. Neville-Neil, The Design and Implemen- tation of the FreeBSD Operating System, Addison-Wesley, 57-61,65-66, July 2004. FreeBSD ports 15.quarterly May 4, 2021 TIME(9)
NAME | SYNOPSIS | DESCRIPTION | SEE ALSO
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