adjtime(S-osr5)
adjtime --
correct the time to allow synchronization of the system clock
Syntax
cc . . . -lc
#include <sys/time.h>
#include <sys/clock.h>
int adjtime(struct timeval *delta, struct timeval *olddelta);
Description
adjtime adjusts the system's notion of the current time,
as returned by
gettimeofday(S-osr5),
advancing or retarding it by the amount of time specified in the
timeval structure pointed to by delta.
This call is used by NTP (Network Time Protocol)
to synchronize the system clocks of the systems
in a local area network.
Parameters described on the
clock(HW)
manual page control the
adjtime( )
functionality.
The adjustment is effected by speeding up (if the adjustment is
positive) or slowing down (if the adjustment is negative) the
system's clock by some small percentage, generally a fraction of one
percent. Thus, the time is always a monotonically increasing
function.
If the requested adjustment can be performed
in less than one second
(determined by the maximum rate specified by
the clock_drift variable described on the
clock(HW)
manual page),
then the adjustment is performed
``smoothly'' over the course of one second.
If the adjustment cannot be performed
in less than one second,
it is performed at the clock_drift rate.
A time correction from an earlier call to adjtime may not
be finished when adjtime is called again. If
delta is NULL, then olddelta returns
information on the previous adjtime call and there is no
effect on the time correction as a result of this call. If
olddelta is not NULL, then the structure it
points to contains, on return, the time still to be corrected from
the earlier call. If olddelta is NULL, the
information is not returned.
Only a process with an effective user ID of 0 can adjust
the system clock.
Return values
On success, adjtime returns 0. On failure,
adjtime returns -1 and sets errno to identify
the error.
Diagnostics
In the following conditions, adjtime fails and sets
errno to:
[EFAULT]-
delta or olddelta points outside the process's
allocated address space, or olddelta points to a region of
the process' allocated address space that is not writable.
[EPERM]-
The calling process does not have an effective user ID of 0.
Files
/lib/libc.a-
linking library
Differences between versions
The high-precision system clock that is implemented
on SCO OpenServer Release 5.0.6 and later releases
improves the precision of
adjtime( ).
When using
adjtime( )
on earlier releases that do not support
the high-precision system clock,
do not call the <sys/clock.h> header file.
See also
clock(HW),
date(C),
gettimeofday(S-osr5),
settimeofday(S-osr5),
stime(S-osr5)
Standards conformance
adjtime is conformant with:
AT&T SVID Issue 3.
© 2005 System Services (S-osr5)
SCO OpenServer Release 6.0.0 -- 02 June 2005