1 .\" Copyright (c) 2006 by Michael Kerrisk <mtk.manpages@gmail.com>
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25 .TH ADJTIME 3 2013-10-07 "Linux" "Linux Programmer's Manual"
27 adjtime \- correct the time to synchronize the system clock
30 .BI "int adjtime(const struct timeval *" delta ", struct timeval *" olddelta );
34 Feature Test Macro Requirements for glibc (see
35 .BR feature_test_macros (7)):
43 function gradually adjusts the system clock (as returned by
44 .BR gettimeofday (2)).
45 The amount of time by which the clock is to be adjusted is specified
46 in the structure pointed to by
48 This structure has the following form:
53 time_t tv_sec; /* seconds */
54 suseconds_t tv_usec; /* microseconds */
61 is positive, then the system clock is speeded up by some
62 small percentage (i.e., by adding a small
63 amount of time to the clock value in each second) until the adjustment
67 is negative, then the clock is slowed down in a similar fashion.
69 If a clock adjustment from an earlier
71 call is already in progress
72 at the time of a later
76 is not NULL for the later call, then the earlier adjustment is stopped,
77 but any already completed part of that adjustment is not undone.
81 is not NULL, then the buffer that it points to is used to return
82 the amount of time remaining from any previous adjustment that
83 has not yet been completed.
88 On failure, \-1 is returned, and
90 is set to indicate the error.
96 is outside the permitted range.
99 The caller does not have sufficient privilege to adjust the time.
102 capability is required.
104 .SS Multithreading (see pthreads(7))
107 function is thread-safe.
113 makes to the clock is carried out in such a manner that the clock
114 is always monotonically increasing.
117 to adjust the time prevents the problems that can be caused for certain
120 by abrupt positive or negative jumps in the system time.
123 is intended to be used to make small adjustments to the system time.
124 Most systems impose a limit on the adjustment that can be specified in
126 In the glibc implementation,
128 must be less than or equal to (INT_MAX / 1000000 \- 2)
129 and greater than or equal to (INT_MIN / 1000000 + 2)
130 (respectively 2145 and \-2145 seconds on i386).
133 .\" http://sourceware.org/bugzilla/show_bug?id=2449
134 .\" http://bugzilla.kernel.org/show_bug.cgi?id=6761
137 was specified as NULL,
138 no valid information about the outstanding clock adjustment was returned in
140 (In this circumstance,
142 should return the outstanding clock adjustment, without changing it.)
144 .\" Thanks to the new adjtimex() ADJ_OFFSET_SS_READ flag
145 on systems with glibc 2.8 or later and
146 Linux kernel 2.6.26 or later.
149 .BR gettimeofday (2),
152 This page is part of release 3.67 of the Linux
155 A description of the project,
156 information about reporting bugs,
157 and the latest version of this page,
159 \%http://www.kernel.org/doc/man\-pages/.