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);
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13       int ntp_gettimex(struct ntptimeval *ntv);
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DESCRIPTION

16       Both  of  these APIs return information to the caller via the ntv argu‐
17       ment, a structure of the following type:
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19           struct ntptimeval {
20               struct timeval time;    /* Current time */
21               long maxerror;          /* Maximum error */
22               long esterror;          /* Estimated error */
23               long tai;               /* TAI offset */
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25               /* Further padding bytes allowing for future expansion */
26           };
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28       The fields of this structure are as follows:
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30       time   The current time, expressed as a timeval structure:
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32                  struct timeval {
33                      time_t      tv_sec;   /* Seconds since the Epoch */
34                      suseconds_t tv_usec;  /* Microseconds */
35                  };
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37       maxerror
38              Maximum error, in microseconds.  This value can  be  initialized
39              by ntp_adjtime(3), and is increased periodically (on Linux: each
40              second), but is clamped to an upper limit (the  kernel  constant
41              NTP_PHASE_MAX, with a value of 16,000).
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43       esterror
44              Estimated  error,  in  microseconds.   This value can be set via
45              ntp_adjtime(3) to contain an estimate of the difference  between
46              the  system clock and the true time.  This value is not used in‐
47              side the kernel.
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49       tai    TAI (Atomic International Time) offset.
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51       ntp_gettime() returns an ntptimeval structure in which the time, maxer‐
52       ror, and esterror fields are filled in.
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54       ntp_gettimex()  performs  the  same task as ntp_gettime(), but also re‐
55       turns information in the tai field.
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RETURN VALUE

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

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

67       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
68       tributes(7).
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70       ┌───────────────────────────────┬───────────────┬─────────┐
71       │Interface                      │ Attribute     │ Value   │
72       ├───────────────────────────────┼───────────────┼─────────┤
73       │ntp_gettime(), ntp_gettimex()  │ Thread safety │ MT-Safe │
74       └───────────────────────────────┴───────────────┴─────────┘

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 5.10 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                             2020-11-01                    NTP_GETTIME(3)
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