| ADJTIME(2) | System Calls Manual | ADJTIME(2) |
adjtime — correct
the time to allow synchronization of the system clock
#include
<sys/time.h>
int
adjtime(const
struct timeval *delta,
struct timeval
*olddelta);
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.
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.
adjtime() will fail if:
date(1), gettimeofday(2), timed(8), timedc(8)
R. Gusella and S. Zatti, TSP: The Time Synchronization Protocol for UNIX 4.3BSD.
The adjtime() function call appeared in
4.3BSD.
| June 4, 1993 | BSD 4.3 |