ADJTIME(2)ADJTIME(2)NAMEadjtime - correct the time to allow synchronization of the system clock
SYNOPSIS
#include <sys/time.h>
adjtime(delta, olddelta)
struct timeval *delta;
struct timeval *olddelta;
DESCRIPTION
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
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 non-zero, then
the structure pointed to will contain, upon return, the number of
microseconds still to be corrected 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 bring
them to the average network time.
The call adjtime(2) is restricted to the super-user.
RETURN VALUE
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.
ERRORS
The following error codes may be set in errno:
[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.
SEE ALSOdate(1), gettimeofday(2), timed(8), timedc(8),
TSP: The Time Synchronization Protocol for UNIX 4.3BSD, R. Gusella and
S. Zatti
4.3 Berkeley Distribution May 15, 1986 ADJTIME(2)