ntp_gettime, ntp_gettimex - get time parameters (NTP daemon interface)
#include <sys/timex.h>
int ntp_gettime(struct ntptimeval *ntv);
int ntp_gettimex(struct ntptimeval *ntv);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:
The current time, expressed as a timeval structure:
struct timeval {
time_t tv_sec; /* Seconds since the Epoch */
suseconds_t tv_usec; /* Microseconds */
};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).
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 (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.
The return values for ntp_gettime() and ntp_gettimex() are as for adjtimex(2). Given a correct pointer argument, these functions always succeed.
The ntp_gettime() function is available since glibc 2.1. The ntp_gettimex() function is available since glibc 2.12.
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
| ntp_gettime(), ntp_gettimex() | Thread safety | MT-Safe |
ntp_gettime() is described in the NTP Kernel Application Program Interface. ntp_gettimex() is a GNU extension.
adjtimex(2), ntp_adjtime(3), time(7)
NTP "Kernel Application Program Interface"
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