ntp_adjtime(2) (man pages section 2: System Calls)

man pages section 2: System Calls

ntp_adjtime(2)

NAME

ntp_adjtime- adjust local clock parameters

SYNOPSIS

#include <sys/timex.h>

tptr

DESCRIPTION

The ntp_adjtime() function adjusts the parameters used to discipline the local clock, according to the values in the struct timex pointed to by tptr. Before returning, it fills in the structure with the most recent values kept in the kernel.

The adjustment is effected in part by speeding up or slowing down the clock, as necessary, and in part by phase-locking onto a once-per second pulse (PPS) provided by a driver, if available.

struct timex {
    uint32_t modes;        /* clock mode bits (w) */
    int32_t  offset;       /* time offset (us) (rw) */
    int32_t  freq;         /* frequency offset (scaled ppm) (rw) */
    int32_t  maxerror;     /* maximum error (us) (rw) */
    int32_t  esterror;     /* estimated error (us) (rw) */
    int32_t  status;       /* clock status bits (rw) */
    int32_t  constant;     /* pll time constant (rw) */
    int32_t  precision;    /* clock precision (us) (r) */
    int32_t  tolerance;    /* clock frequency tolerance
                              (scaled ppm) (r) */
    int32_t  ppsfreq;      /* pps frequency (scaled ppm) (r) */
    int32_t  jitter;       /* pps jitter (us) (r) */
    int32_t  shift;        /* interval duration (s) (shift) (r) */
    int32_t  stabil;       /* pps stability (scaled ppm) (r) */
    int32_t  jitcnt;       /* jitter limit exceeded (r) */
    int32_t  calcnt;       /* calibration intervals (r) */
    int32_t  errcnt;       /* calibration errors (r) */
    int32_t  stbcnt;       /* stability limit exceeded (r) */
};

RETURN VALUES

Upon successful completion, ntp_adjtime() returns the current clock state (see <sys/timex.h>). Otherwise, it returns -1 and sets errno to indicate the error.

ERRORS

The ntp_adjtime() function will fail if:

EFAULT: The tptr argument is an invalid pointer.
EINVAL: The constant member of the structure pointed to by tptr is less than 0 or greater than 30.
EPERM: The user is not super-user.