исправить время для синхронизации системных часов (correct the time to synchronize the system clock)
Имя (Name)
adjtime - correct the time to synchronize the system clock
Синопсис (Synopsis)
#include <sys/time.h>
int adjtime(const struct timeval *delta, struct timeval *olddelta);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
adjtime():
Since glibc 2.19:
_DEFAULT_SOURCE
Glibc 2.19 and earlier:
_BSD_SOURCE
Описание (Description)
The adjtime() function gradually adjusts the system clock (as
returned by gettimeofday(2)). The amount of time by which the
clock is to be adjusted is specified in the structure pointed to
by delta. This structure has the following form:
struct timeval {
time_t tv_sec; /* seconds */
suseconds_t tv_usec; /* microseconds */
};
If the adjustment in delta is positive, then the system clock is
speeded up by some small percentage (i.e., by adding a small
amount of time to the clock value in each second) until the
adjustment has been completed. If the adjustment in delta is
negative, then the clock is slowed down in a similar fashion.
If a clock adjustment from an earlier adjtime() call is already
in progress at the time of a later adjtime() call, and delta is
not NULL for the later call, then the earlier adjustment is
stopped, but any already completed part of that adjustment is not
undone.
If olddelta is not NULL, then the buffer that it points to is
used to return the amount of time remaining from any previous
adjustment that has not yet been completed.
Возвращаемое значение (Return value)
On success, adjtime() returns 0. On failure, -1 is returned, and
errno is set to indicate the error.
Ошибки (Error)
EINVAL The adjustment in delta is outside the permitted range.
EPERM The caller does not have sufficient privilege to adjust
the time. Under Linux, the CAP_SYS_TIME capability is
required.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│adjtime() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
4.3BSD, System V.
Примечание (Note)
The adjustment that adjtime() makes to the clock is carried out
in such a manner that the clock is always monotonically
increasing. Using adjtime() to adjust the time prevents the
problems that can be caused for certain applications (e.g.,
make(1)) by abrupt positive or negative jumps in the system time.
adjtime() is intended to be used to make small adjustments to the
system time. Most systems impose a limit on the adjustment that
can be specified in delta. In the glibc implementation, delta
must be less than or equal to (INT_MAX / 1000000 - 2) and greater
than or equal to (INT_MIN / 1000000 + 2) (respectively 2145 and
-2145 seconds on i386).
Ошибки (баги) (Bugs)
A longstanding bug meant that if delta was specified as NULL, no
valid information about the outstanding clock adjustment was
returned in olddelta. (In this circumstance, adjtime() should
return the outstanding clock adjustment, without changing it.)
This bug is fixed on systems with glibc 2.8 or later and Linux
kernel 2.6.26 or later.
Смотри также (See also)
adjtimex(2), gettimeofday(2), time(7)
