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 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.

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"

COLOPHON

       This page is part of release 5.10 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                                              2020-11-01                                     NTP_GETTIME(3)