Section (3) ntp_gettime
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.
COLOPHON
This page is part of release 4.16 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> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END |