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NAME

       adjtime - smoothly tune kernel clock

SYNOPSIS

       #include <sys/time.h>

       int adjtime(const struct timeval *delta, struct timeval *olddelta);

DESCRIPTION

       This function speeds up or slows down the system clock in order to make
       a gradual adjustment.  This ensures that the calendar time reported  by
       the  system  clock  is always monotonically increasing, which might not
       happen if you simply set the clock.

       The delta argument specifies a relative adjustment to be  made  to  the
       clock  time.   If  negative, the system clock is slowed down fora while
       until it has lost this much elapsed  time.   If  positive,  the  system
       clock is speeded up for a while.

       If  the  olddelta  argument is not a null pointer, the adjtime function
       returns information about any previous time adjustment that has not yet
       completed.

       This  function is typically used to synchronize the clocks of computers
       in a local network.  You must be a privileged user to use it.

RETURN VALUE

       The adjtime function returns 0 on success and -1 on  failure  and  sets
       the external variable errno accordingly.

ERRORS

       EPERM  The  calling  process  does not have enough privileges to access
              the clock.

NOTE

       With  a  Linux  kernel,  you  can  use  the  adjtimex(2)  function   to
       permanently change the system clock speed.

CONFORMING TO

       This function is derived from 4.3 BSD and SVr4.

SEE ALSO

       adjtimex(2), settimeofday(2)