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adjtime - correct the time to allow synchronization of the system clock

 

NAME

      adjtime - correct the time to allow synchronization of the system clock
 

LIBRARY

      Standard C Library (libc, -lc)
 

SYNOPSIS

      #include <sys/time.h>
 
      int
      adjtime(const struct timeval *delta, struct timeval *olddelta);
 

DESCRIPTION

      The adjtime() system call makes small adjustments to the system time, as
      returned by gettimeofday(2), advancing or retarding it by the time speci‐
      fied by the timeval delta.  If delta is negative, the clock is slowed
      down by incrementing it more slowly than normal until the correction is
      complete.  If delta is positive, a larger increment than normal is used.
      The skew used to perform the correction is generally a fraction of one
      percent.  Thus, the time is always a monotonically increasing function.
      A time correction from an earlier call to adjtime() may not be finished
      when adjtime() is called again.  If olddelta is not a null pointer, the
      structure pointed to will contain, upon return, the number of microsec‐
      onds still to be corrected from the earlier call.
 
      This call may be used by time servers that synchronize the clocks of com‐
      puters in a local area network.  Such time servers would slow down the
      clocks of some machines and speed up the clocks of others to bring them
      to the average network time.
 
      The adjtime() system call is restricted to the super-user.
      The adjtime() function returns the value 0 if successful; otherwise the
      value -1 is returned and the global variable errno is set to indicate the
      error.
 

ERRORS

      The adjtime() system call will fail if:
 
      [EFAULT]           An argument points outside the process’s allocated
                         address space.
 
      [EPERM]            The process’s effective user ID is not that of the
                         super-user.
      date(1), gettimeofday(2), timed(8), timedc(8)
 
      R. Gusella and S. Zatti, TSP: The Time Synchronization Protocol for UNIX
      4.3BSD.
 

HISTORY

      The adjtime() system call appeared in 4.3BSD.
 

Sections

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.