NAME
adjtime —
correct the time to allow
synchronization of the system clock
LIBRARY
library “libc”
SYNOPSIS
#include
<sys/time.h>
int
adjtime(const
struct timeval *delta,
struct timeval
*olddelta);
DESCRIPTION
Theadjtime()
system call 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 not a null pointer, 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
adjtime()
system call is restricted to the super-user.
RETURN VALUES
The adjtime() function returns the
value 0 if successful; otherwise the value -1 is returned and
the global variable errno is set to indicate the
error.
ERRORS
The adjtime() system call 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() system call appeared in
4.3BSD.