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).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.
See Also
- adjtimex(2),
- ntp_adjtime(3),
- time(7)
NTP "Kernel Application Program Interface"