FreeBSD 7.0 manual page repository

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boottime, time_second, time_uptime - system time variables

 

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 system boot time.
 
      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 accurately and in an atomic manner.  Similarly, the
      binuptime(9), getbinuptime(9), microuptime(9), getmicrouptime(9),
      nanouptime(9), and getnanouptime(9) functions can be used to get the time
      elapse since boot more accurately and in an atomic manner.  The boottime
      variable may be read and written without special precautions.
      clock_settime(2), ntp_adjtime(2), settimeofday(2), bintime(9),
      binuptime(9), getbintime(9), getbinuptime(9), getmicrotime(9),
      getmicrouptime(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/papers/timecounter.ascii.gz.
 
      Marshall Kirk McKusick and George V. Neville-Neil, The Design and
      Implementation of the FreeBSD Operating System, Addison-Wesley,
      57-61,65-66, July 2004.
 

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Based on BSD UNIX
FreeBSD is an advanced operating system for x86 compatible (including Pentium and Athlon), amd64 compatible (including Opteron, Athlon64, and EM64T), UltraSPARC, IA-64, PC-98 and ARM architectures. It is derived from BSD, the version of UNIX developed at the University of California, Berkeley. It is developed and maintained by a large team of individuals. Additional platforms are in various stages of development.