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adjtime(2) [bsd man page]

ADJTIME(2)							System Calls Manual							ADJTIME(2)

NAME
adjtime - correct the time to allow synchronization of the system clock SYNOPSIS
#include <sys/time.h> adjtime(delta, olddelta) struct timeval *delta; struct timeval *olddelta; DESCRIPTION
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 per- cent. 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-zero, then 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(2) is restricted to the super-user. RETURN VALUE
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
The following error codes may be set in errno: [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), TSP: The Time Synchronization Protocol for UNIX 4.3BSD, R. Gusella and S. Zatti NOTES (PDP-11) Adjtime(2) calls are executed immediately, not over a period of time, therefore, the olddelta return values for an adjtime(2) call will always be zero. 4.3 Berkeley Distribution May 15, 1986 ADJTIME(2)

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adjtime(2)							   System Calls 							adjtime(2)

NAME
adjtime - 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 system's clock by some small percentage, generally a fraction of one percent. 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 structure 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 effective 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 ALSO
date(1), gettimeofday(3C), privileges(5) SunOS 5.10 20 Jan 2003 adjtime(2)

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