ntp_gettime(3) Linux Man Page

Name

ntp_gettime, ntp_gettimex - get time parameters (NTP daemon interface)

Library

Standard C library ( libc ", " -lc )

Synopsis

#include <sys/timex.h> 
int ntp_gettime(struct ntptimeval * ntv );
int ntp_gettimex(struct ntptimeval * ntv );

Description

Both of these APIs return information to the caller via the ntv argument, a structure of the following type:

struct ntptimeval {
    struct timeval time;    /* Current time */
    long maxerror;          /* Maximum error */
    long esterror;          /* Estimated error */
    long tai;               /* TAI offset */

    /* Further padding bytes allowing for future expansion */
};

The fields of this structure are as follows:

time The current time, expressed as a timeval structure:

struct timeval {
    time_t      tv_sec;   /* Seconds since the Epoch */
    suseconds_t tv_usec;  /* Microseconds */
};

maxerror Maximum error, in microseconds. This value can be initialized by ntp_adjtime(3), and is increased periodically (on Linux: each second), but is clamped to an upper limit (the kernel constant NTP_PHASE_MAX ,with a value of 16,000).

esterror Estimated error, in microseconds. This value can be set via ntp_adjtime(3) to contain an estimate of the difference between the system clock and the true time. This value is not used inside the kernel.

tai TAI (Atomic International Time) offset.

ntp_gettime() returns an ntptimeval structure in which the time, maxerror, and esterror fields are filled in.

ntp_gettimex() performs the same task as ntp_gettime() but also returns information in the tai field.

Return Value

The return values for ntp_gettime() and ntp_gettimex() are as for adjtimex(2). Given a correct pointer argument, these functions always succeed.

Attributes

For an explanation of the terms used in this section, see attributes(7). allbox; lbx lb lb T{ ntp_gettime()ntp_gettimex()

Interface	Attribute	Value
T}	Thread safety	MT-Safe

Standards

ntp_gettime() NTP Kernel Application Program Interface.

ntp_gettimex() GNU.

History

ntp_gettime() glibc 2.1.

ntp_gettimex() glibc 2.12.

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