名稱
adjtimex - 調內核時鐘
內容簡介
#include <sys/timex.h> int adjtimex(struct timex *buf); |
描述
Linux使用大衛L. Mills的時鐘調整演算法（參見RFC1305）。 adjtimex()系統調用讀取和任選設置該演算法的調整參數。這需要一個指針的TIMEX結構，更新內核參數字段值，並返回相同的結構與當前的內核值。這種結構的聲明如下：
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 ”字段確定的參數，如果有的話就設置。它可能包含一個按位或組合的零個或多個以下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() */ |
普通用戶限制到零值模式mode。只有超級用戶可以設置任何參數。
返回值
成功，adjtimex() 返回時鐘狀態：
#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 */ |
如果失敗，adjtimex（）返回-1，並設置errno。
錯誤
| 標籤 | 描述 |
|---|---|
| EFAULT | buf does not point to writable memory. |
| EINVAL | An attempt is made to setbuf.offset to a value outside the range -131071 to +131071,or to set buf.status to a value other than those listed above,or to set buf.tick to a value outside the range 900000/HZ to 1100000/HZ, where HZ is the system timer interrupt frequency. |
| EPERM | buf.mode is non-zero and the caller does not have sufficient privilege.Under Linux the CAP_SYS_TIME capability is required. |
遵循於
adjtimex() 是Linux特有的，並且不應該被用在程式準備移植. 查看adjtime（3）用於調整系統時鐘的方法，更輕便，但彈性較差。