名称
adjtimex - 调内核时钟
内容简介
#include <sys/timex.h> int adjtimex(struct timex *buf) |
描述
Linux使用大卫L. Mills的时钟调整算法（参见RFC1305）。ꂭjtimex()系统调用读取和任选设置该算法的调整参数。这需要一个指针的TIMEX结构，更新内核参数字段值，并返回相同的结构与当前的内核值。这种结构的声明如下：
struct timex {
int modes /* mode selector */
long offset /* time offset (usec) */
long freq /* frequency offset (scaled ppm) */
long maxerror /* maximum error (usec) */
long esterror /* estimated error (usec) */
int status /* clock command/status */
long constant /* pll time constant */
long precision /* clock precision (usec) (read only) */
long tolerance /* clock frequency tolerance (ppm)
(read only) */
struct timeval time /* current time (read only) */
long tick /* usecs between clock ticks */
}
|
“modes%uA0”字段确定的参数，如果有的话就设置。它可能包含一个按位或组合的零个或多个以下bits：
#define ADJ_OFFSET 0x0001 /* time offset */ #define ADJ_FREQUENCY 0x0002 /* frequency offset */ #define ADJ_MAXERROR 0x0004 /* maximum time error */ #define ADJ_ESTERROR 0x0008 /* estimated time error */ #define ADJ_STATUS 0x0010 /* clock status */ #define ADJ_TIMECONST 0x0020 /* pll time constant */ #define ADJ_TICK 0x4000 /* tick value */ #define ADJ_OFFSET_SINGLESHOT 0x8001 /* old-fashioned adjtime() */ |
普通用户限制到零值模式mode。只有超级用户可以设置任何参数。
返回值
成功，adjtimex() 返回时钟状态：
#define TIME_OK 0 /* clock synchronized */ #define TIME_INS 1 /* insert leap second */ #define TIME_DEL 2 /* delete leap second */ #define TIME_OOP 3 /* leap second in progress */ #define TIME_WAIT 4 /* leap second has occurred */ #define TIME_BAD 5 /* clock not synchronized */ |
如果失败，adjtimex（）返回-1，并设置errno。
错误
| 标签 | 描述 |
|---|---|
| EFAULT | buf%uA0does not point to writable memory. |
| EINVAL | An attempt is made to setbuf.offset%uA0to a value outside the range -131071 to +131071,or to set%uA0buf.status%uA0to a value other than those listed above,or to set%uA0buf.tick%uA0to a value outside the range 900000/HZ%uA0to 1100000/HZ, where%uA0HZ%uA0is the system timer interrupt frequency. |
| EPERM | buf.mode%uA0is non-zero and the caller does not have sufficient privilege.Under Linux the%uA0CAP_SYS_TIMEꃊpability is required. |
遵循于
adjtimex() 是Linux特有的，并且不应该被用在程序准备移植.%uA0查看adjtime（3）用于调整系统时钟的方法，更轻便，但弹性较差。