linux man page for ntp_gettime

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 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 sec-
	      ond), 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" <http://www.slac.stanford.edu/comp/unix/package/rtems/src/ssrlApps/ntpNanoclock/api.htm>

Linux								    2017-09-15							    NTP_GETTIME(3)