#include <sys/timex.h>
int adjtimex(struct timex * buf );
Linux uses David L. Mills' clock adjustment algorithm (see RFC 1305). The system call adjtimex () reads and optionally sets adjustment parameters for this algorithm. It takes a pointer to a timex structure, updates kernel parameters from field values, and returns the same structure with current kernel values. This structure is declared as follows:
Linux uses David L. Mills' clock adjustment algorithm (see RFC 1305). The system call adjtimex () reads and optionally sets adjustment parameters for this algorithm. It takes a pointer to a timex structure, updates kernel parameters from field values, and returns the same structure with current kernel values. This structure is declared as follows:
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 */ };
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 */ }; The modes field determines which parameters, if any, to set. It may contain a
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 */ }; The modes field determines which parameters, if any, to set. It may contain a combination of zero or more of the following bits:
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 */ }; The modes field determines which parameters, if any, to set. It may contain a combination of zero or more of the following 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() */
#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() */ Ordinary users are restricted to a zero value for mode . Only the superuser may set any parameters.
#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() */ Ordinary users are restricted to a zero value for mode . Only the superuser may set any parameters.
On success, adjtimex () returns the clock state:
On success, adjtimex () returns the clock state:
#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 */
#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 */ On failure, adjtimex () returns -1 and sets errno .
EFAULT buf does not point to writable memory.
EINVAL An attempt is made to set buf.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
EINVAL An attempt is made to set buf.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 to
EINVAL An attempt is made to set buf.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 to where HZ is the system timer interrupt frequency.
EPERM buf.mode is nonzero and the caller does not have sufficient privilege. Under Linux the CAP_SYS_TIME capability is required.
adjtimex () is Linux-specific and should not be used in programs intended to be portable. See adjtime (3) for a more portable, but less flexible, method of adjusting the system clock.
settimeofday (2) adjtime (3) capabilities (7)
