1 .\" $NetBSD: time.9,v 1.1 1995/11/25 21:24:53 perry Exp $
3 .\" Copyright (c) 1994 Christopher G. Demetriou
4 .\" All rights reserved.
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16 .\" This product includes software developed by Christopher G. Demetriou
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41 .Nd system time variables
45 .Vt extern struct timeval boottime ;
46 .Vt extern time_t time_second ;
47 .Vt extern time_t time_uptime ;
51 variable holds the estimated system boot time.
52 This time is initially set when the system boots, either from the RTC, or from a
53 time estimated from the system's root filesystem.
54 When the current system time is set, stepped by
56 or a new time is read from the RTC as the system resumes,
58 is recomputed as new_time - uptime.
66 variable is the system's
72 variable is the number of seconds since boot.
82 functions can be used to get the current time more accurately and in an
88 .Xr getmicrouptime 9 ,
92 functions can be used to get the time elapse since boot more accurately
93 and in an atomic manner.
96 variable may be read and written without special precautions.
97 It is adjusted when the phase of the system time changes.
107 .Xr getmicrouptime 9 ,
109 .Xr getnanouptime 9 ,
115 .%A "Poul-Henning Kamp"
116 .%T "Timecounters: Efficient and precise timekeeping in SMP kernels"
117 .%J "Proceedings of EuroBSDCon 2002, Amsterdam"
118 .%O /usr/share/doc/papers/timecounter.ascii.gz
121 .%A "Marshall Kirk McKusick"
122 .%A "George V. Neville-Neil"
123 .%B "The Design and Implementation of the FreeBSD Operating System"