1NTP_GETTIME(3)             Linux Programmer's Manual            NTP_GETTIME(3)
2
3
4

NAME

6       ntp_gettime, ntp_gettimex  - get time parameters (NTP daemon interface)
7

SYNOPSIS

9       #include <sys/timex.h>
10
11       int ntp_gettime(struct ntptimeval *ntv);
12
13       int ntp_gettimex(struct ntptimeval *ntv);
14

DESCRIPTION

16       Both  of  these APIs return information to the caller via the ntv argu‐
17       ment, a structure of the following type:
18
19           struct ntptimeval {
20               struct timeval time;        /* Current time */
21               long int maxerror;          /* Maximum error */
22               long int esterror;          /* Estimated error */
23               long int tai;               /* TAI offset */
24
25               /* Further padding bytes allowing for future expansion */
26           };
27
28       The fields of this structure are as follows:
29
30       time   The current time, expressed as a timeval structure:
31
32                  struct timeval {
33                      time_t      tv_sec;   /* Seconds since the Epoch */
34                      suseconds_t tv_usec;  /* Microseconds */
35                  };
36
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).
42
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
47              inside the kernel.
48
49       tai    TAI (Atomic International Time) offset.
50
51       ntp_gettime() returns an ntptimeval structure in which the time, maxer‐
52       ror, and esterror fields are filled in.
53
54       ntp_gettimex()  performs  the  same  task  as  ntp_gettime(),  but also
55       returns information in the tai field.
56

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.
61

VERSIONS

63       The ntp_gettime() function is available since glibc 2.1.  The  ntp_get‐
64       timex() function is available since glibc 2.12.
65

ATTRIBUTES

67       For   an   explanation   of   the  terms  used  in  this  section,  see
68       attributes(7).
69
70       ┌───────────────────────────────┬───────────────┬─────────┐
71Interface                      Attribute     Value   
72       ├───────────────────────────────┼───────────────┼─────────┤
73ntp_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.
78

SEE ALSO

80       adjtimex(2) ntp_adjtime(3), time(7)
81
82       NTP "Kernel Application Program Interface"
83http://www.slac.stanford.edu/comp/unix/package/rtems/src/ssrlApps/
84       ntpNanoclock/api.htm⟩
85

COLOPHON

87       This page is part of release 5.02 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/.
91
92
93
94Linux                             2017-09-15                    NTP_GETTIME(3)
Impressum