adjtime - correct the time to allow synchronization of the
adjtime(const struct timeval *delta, struct timeval
adjtime() makes small adjustments to the system time, as returned by
gettimeofday(2), advancing or retarding it by the time specified by the
timeval delta. If delta is negative, the clock is slowed
down by incrementing
it more slowly than normal until the correction is
delta is positive, a larger increment than normal is used.
The skew used
to perform the correction is generally a fraction of one
the time is always a monotonically increasing function. A
from an earlier call to adjtime() may not be finished
is called again. If olddelta is non-null, the structure
pointed to will
contain, upon return, the number of microseconds still to be
from the earlier call.
This call may be used by time servers that synchronize the
clocks of computers
in a local area network. Such time servers would
slow down the
clocks of some machines and speed up the clocks of others to
to the average network time.
The call adjtime() is restricted to the superuser.
A return value of 0 indicates that the call succeeded. A
return value of
-1 indicates that an error occurred, and in this case an error code is
stored in the global variable errno.
adjtime() will fail if:
[EFAULT] Either of the arguments point outside the process's allocated
[EPERM] The process's effective user ID is not that of
date(1), gettimeofday(2), timed(8), timedc(8)
R. Gusella and S. Zatti, TSP: The Time Synchronization
Protocol for UNIX
The adjtime() function call appeared in 4.3BSD.
OpenBSD 3.6 June 4, 1993
[ Back ]