1NTP_GETTIME(3)             Linux Programmer's Manual            NTP_GETTIME(3)
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NAME

6       ntp_gettime, ntp_gettimex  - get time parameters (NTP daemon interface)
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SYNOPSIS

9       #include <sys/timex.h>
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11       int ntp_gettime(struct ntptimeval *ntv);
12       int ntp_gettimex(struct ntptimeval *ntv);
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DESCRIPTION

15       Both  of  these APIs return information to the caller via the ntv argu‐
16       ment, a structure of the following type:
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18           struct ntptimeval {
19               struct timeval time;    /* Current time */
20               long maxerror;          /* Maximum error */
21               long esterror;          /* Estimated error */
22               long tai;               /* TAI offset */
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24               /* Further padding bytes allowing for future expansion */
25           };
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27       The fields of this structure are as follows:
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29       time   The current time, expressed as a timeval structure:
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31                  struct timeval {
32                      time_t      tv_sec;   /* Seconds since the Epoch */
33                      suseconds_t tv_usec;  /* Microseconds */
34                  };
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36       maxerror
37              Maximum error, in microseconds.  This value can  be  initialized
38              by ntp_adjtime(3), and is increased periodically (on Linux: each
39              second), but is clamped to an upper limit (the  kernel  constant
40              NTP_PHASE_MAX, with a value of 16,000).
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42       esterror
43              Estimated  error,  in  microseconds.   This value can be set via
44              ntp_adjtime(3) to contain an estimate of the difference  between
45              the  system clock and the true time.  This value is not used in‐
46              side the kernel.
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48       tai    TAI (Atomic International Time) offset.
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50       ntp_gettime() returns an ntptimeval structure in which the time, maxer‐
51       ror, and esterror fields are filled in.
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53       ntp_gettimex()  performs  the  same task as ntp_gettime(), but also re‐
54       turns information in the tai field.
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RETURN VALUE

57       The return values for ntp_gettime() and ntp_gettimex() are as for  adj‐
58       timex(2).   Given  a  correct  pointer argument, these functions always
59       succeed.
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VERSIONS

62       The ntp_gettime() function is available since glibc 2.1.  The  ntp_get‐
63       timex() function is available since glibc 2.12.
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ATTRIBUTES

66       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
67       tributes(7).
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69       ┌────────────────────────────────────────────┬───────────────┬─────────┐
70       │Interface                                   │ Attribute     │ Value   │
71       ├────────────────────────────────────────────┼───────────────┼─────────┤
72       │ntp_gettime(), ntp_gettimex()               │ Thread safety │ MT-Safe │
73       └────────────────────────────────────────────┴───────────────┴─────────┘
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CONFORMING TO

76       ntp_gettime() is described in the NTP Kernel Application Program Inter‐
77       face.  ntp_gettimex() is a GNU extension.
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SEE ALSO

80       adjtimex(2), ntp_adjtime(3), time(7)
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82       NTP "Kernel Application Program Interface"
83       ⟨http://www.slac.stanford.edu/comp/unix/package/rtems/src/ssrlApps/
84       ntpNanoclock/api.htm⟩
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COLOPHON

87       This page is part of release 5.12 of the Linux man-pages project.  A
88       description of the project, information about reporting bugs, and the
89       latest version of this page, can be found at
90       https://www.kernel.org/doc/man-pages/.
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94Linux                             2021-03-22                    NTP_GETTIME(3)
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