NAME
adjtime —
correct the time to allow
synchronization of the system clock
SYNOPSIS
#include
<sys/time.h>
int
adjtime(const
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-nil, 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()
is restricted to the super-user.
RETURN VALUES
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
adjtime() 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.
SEE ALSO
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() function call appeared in
4.3BSD.