man:ntp_gettimex
NTP_GETTIME(3) Linux Programmer's Manual NTP_GETTIME(3)
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 argu- ment, 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, maxer- ror, 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 adj- timex(2). Given a correct pointer argument, these functions always succeed.
VERSIONS
The ntp_gettime() function is available since glibc 2.1. The ntp_get- timex() function is available since glibc 2.12.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
allbox; lbw30 lb lb l l l. Interface Attribute Value T{ ntp_gettime(), ntp_gettimex() T} Thread safety MT-Safe
CONFORMING TO
ntp_gettime() is described in the NTP Kernel Application Program Inter- face. 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 4.16 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/.
Linux 2017-09-15 NTP_GETTIME(3)
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