Name

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

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 int   maxerror;
/* Maximum error */
  long int   esterror;
/* Estimated error */
  long int   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.

VERSIONS

The ntp_gettime() function is available since glibc 2.1. The ntp_gettimex() function is available since glibc 2.12.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface Attribute Value
ntp_gettime(), ntp_gettimex() Thread safety MT-Safe

CONFORMING TO

ntp_gettime() is described in the NTP Kernel Application Program Interface. ntp_gettimex() is a GNU extension.

SEE ALSO

adjtimex(2) ntp_adjtime(3), time(7)

NTP "Kernel Application Program Interface"

COLOPHON

This page is part of release 4.12 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man−pages/.


  Copyright (c) 2016 by Michael Kerrisk <mtk.manpagesgmail.com>

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