Copyright (c) 1994 Christopher G. Demetriou
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This product includes software developed by Christopher G. Demetriou
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$FreeBSD$
.Dd September 17, 2004 .Dt TIME 9 .Os .Sh NAME .Nm boottime , .Nm time_second , .Nm time_uptime .Nd system time variables .Sh SYNOPSIS n sys/time.h
p .Vt extern struct timeval boottime ; .Vt extern time_t time_second ; .Vt extern time_t time_uptime ; .Sh DESCRIPTION The .Va boottime variable holds the system boot time.
p The .Va time_second variable is the system's .Dq wall time clock to the second.
p The .Va time_uptime variable is the number of seconds since boot.
p
The
.Xr bintime 9 ,
.Xr getbintime 9 ,
.Xr microtime 9 ,
.Xr getmicrotime 9 ,
.Xr nanotime 9 ,
and
.Xr getnanotime 9
functions can be used to get the current time more accurately and in an
atomic manner.
Similarly, the
.Xr binuptime 9 ,
.Xr getbinuptime 9 ,
.Xr microuptime 9 ,
.Xr getmicrouptime 9 ,
.Xr nanouptime 9 ,
and
.Xr getnanouptime 9
functions can be used to get the time elapse since boot more accurately
and in an atomic manner.
The
.Va boottime
variable may be read and written without special precautions.
.Sh SEE ALSO
.Xr clock_settime 2 ,
.Xr ntp_adjtime 2 ,
.Xr settimeofday 2 ,
.Xr bintime 9 ,
.Xr binuptime 9 ,
.Xr getbintime 9 ,
.Xr getbinuptime 9 ,
.Xr getmicrotime 9 ,
.Xr getmicrouptime 9 ,
.Xr getnanotime 9 ,
.Xr getnanouptime 9 ,
.Xr microtime 9 ,
.Xr microuptime 9 ,
.Xr nanotime 9 ,
.Xr nanouptime 9
.Rs
.%A "Poul-Henning Kamp"
.%T "Timecounters: Efficient and precise timekeeping in SMP kernels"
.%J "Proceedings of EuroBSDCon 2002, Amsterdam"
.%O /usr/share/doc/papers/timecounter.ascii.gz
.Re
.Rs
.%A "Marshall Kirk McKusick"
.%A "George V. Neville-Neil"
.%B "The Design and Implementation of the FreeBSD Operating System"
.%D "July 2004"
.%I "Addison-Wesley"
.%P "57-61,65-66"
.Re