adjtime(2) System Calls adjtime(2)NAMEadjtime - correct the time to allow synchronization of the system clock
SYNOPSIS
#include <sys/time.h>
int adjtime(struct timeval *delta, struct timeval *olddelta);
DESCRIPTION
The adjtime() function adjusts the system's notion of the current time
as returned by gettimeofday(3C), advancing or retarding it by the
amount of time specified in the struct timeval pointed to by delta.
The adjustment is effected by speeding up (if that amount of time is
positive) or slowing down (if that amount of time is negative) the sys‐
tem's clock by some small percentage, generally a fraction of one per‐
cent. 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 delta is 0, then olddelta returns the status of the effects of the
previous adjtime() call with no effect on the time correction as a
result of this call. If olddelta is not a null pointer, then the struc‐
ture it points to will contain, upon successful return, the number of
seconds and/or microseconds still to be corrected from the earlier
call. If olddelta is a null pointer, the corresponding information will
not be returned.
This call may be used in 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.
Only a processes with appropriate privileges can adjust the time of
day.
The adjustment value will be silently rounded to the resolution of the
system clock.
RETURN VALUES
Upon successful completion, adjtime() returns 0. Otherwise, it returns
−1 and sets errno to indicate the error.
ERRORS
The adjtime() function will fail if:
EFAULT The delta or olddelta argument points outside the process's
allocated address space, or olddelta points to a region of
the process's allocated address space that is not writable.
EINVAL The tv_usec member of delta is not within valid range
(−1000000 to 1000000).
EPERM The {PRIV_SYS_TIME} privilege is not asserted in the effec‐
tive set of the calling process.
Additionally, the adjtime() function will fail for 32-bit interfaces
if:
EOVERFLOW The size of the tv_sec member of the timeval structure
pointed to by olddelta is too small to contain the correct
number of seconds.
SEE ALSOdate(1), gettimeofday(3C), privileges(5)SunOS 5.11 20 Jan 2003 adjtime(2)
