ADJTIME

Section: System Calls (2)
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BSD mandoc
BSD 4.3

NAME

adjtime - correct the time to allow synchronization of the system clock

SYNOPSIS

Fd #include <sys/time.h> Ft int Fn adjtime struct timeval *delta struct timeval *olddelta

DESCRIPTION

Fn Adjtime makes small adjustments to the system time, as returned by gettimeofday(2), advancing or retarding it by the time specified by the timeval Fa delta . If Fa delta is negative, the clock is slowed down by incrementing it more slowly than normal until the correction is complete. If Fa 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 Fn adjtime may not be finished when Fn adjtime is called again. If Fa 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 Fn 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

Fn Adjtime will fail if:

Bq Er EFAULT: An argument points outside the process's allocated address space.
Bq Er EPERM: The process's effective user ID is not that of the super-user.

HISTORY

The Fn adjtime function call appeared in BSD 4.3

This document was created by man2html, using the manual pages.
Time: 16:29:00 GMT, April 18, 2022