projects / unix-history / blame
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|---|---|---|
| ab34755c RG |
1 | .\" Copyright (c) 1980 Regents of the University of California. |
| 2 | .\" All rights reserved. The Berkeley software License Agreement | |
| 3 | .\" specifies the terms and conditions for redistribution. | |
| 4 | .\" | |
| 09cfce6f | 5 | .\" @(#)adjtime.2 1.3 (Berkeley) %G% |
| ab34755c RG |
6 | .\" |
| 7 | .TH ADJTIME 2 "" | |
| 8 | .UC 6 | |
| 9 | .SH NAME | |
| 10 | adjtime \- correct the time to allow synchronization of the system clock | |
| 11 | .SH SYNOPSIS | |
| 12 | .nf | |
| 13 | .ft B | |
| 14 | #include <sys/time.h> | |
| 15 | .PP | |
| 16 | .ft B | |
| 17 | adjtime(delta, olddelta) | |
| 18 | struct timeval *delta; | |
| 19 | struct timeval *olddelta; | |
| 20 | .fi | |
| 21 | .SH DESCRIPTION | |
| 22 | .I Adjtime | |
| 9d26ec35 | 23 | makes small adjustments to the system time, as returned by |
| ab34755c | 24 | .IR gettimeofday (2), |
| 9d26ec35 | 25 | advancing or retarding it |
| 09cfce6f | 26 | by the time specified by the timeval |
| ab34755c | 27 | \fIdelta\fP. |
| ab34755c | 28 | If \fIdelta\fP is negative, the clock is |
| 9d26ec35 MK |
29 | slowed down by incrementing it more slowly than normal until |
| 30 | the correction is complete. | |
| 31 | If \fIdelta\fP is positive, a larger increment than normal | |
| ab34755c | 32 | is used. |
| 9d26ec35 | 33 | The skew used to perform the correction is generally a fraction of one percent. |
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34 | Thus, the time is always |
| 35 | a monotonically increasing function. | |
| 36 | A time correction from an earlier call to \fIadjtime\fP | |
| 37 | may not be finished when \fIadjtime\fP is called again. | |
| 38 | If \fIolddelta\fP is non-zero, | |
| 39 | then the structure pointed to will contain, upon return, the | |
| 40 | number of microseconds still to be corrected | |
| 41 | from the earlier call. | |
| 42 | .PP | |
| 9d26ec35 | 43 | This call may be used by time servers that synchronize the clocks |
| ab34755c RG |
44 | of computers in a local area network. |
| 45 | Such time servers would slow down the clocks of some machines | |
| 46 | and speed up the clocks of others to bring them to the average network time. | |
| 47 | .PP | |
| 48 | The call | |
| 49 | .IR adjtime (2) | |
| 50 | is restricted to the super-user. | |
| ab34755c RG |
51 | .SH "RETURN VALUE |
| 52 | A return value of 0 indicates that the call succeeded. | |
| 53 | A return value of \-1 indicates that an error occurred, and in this | |
| 54 | case an error code is stored in the global variable \fIerrno\fP. | |
| 55 | .SH "ERRORS | |
| 56 | The following error codes may be set in \fIerrno\fP: | |
| 57 | .TP 15 | |
| 58 | [EFAULT] | |
| 59 | An argument points outside the process's allocated address space. | |
| 60 | .TP 15 | |
| 61 | [EPERM] | |
| 62 | The process's effective user ID is not that of the super-user. | |
| 63 | .SH "SEE ALSO" | |
| 64 | date(1), gettimeofday(2), timed(8), timedc(8), | |
| 65 | .br | |
| 66 | \fITSP: The Time Synchronization Protocol for UNIX 4.3BSD\fP, | |
| 67 | R. Gusella and S. Zatti |