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| .TH NTP_GETTIME 3 2021-03-22 "Linux" "Linux Programmer's Manual" |
| .SH NAME |
| ntp_gettime, ntp_gettimex \- get time parameters (NTP daemon interface) |
| .SH SYNOPSIS |
| .nf |
| .B #include <sys/timex.h> |
| .PP |
| .BI "int ntp_gettime(struct ntptimeval *" ntv ); |
| .BI "int ntp_gettimex(struct ntptimeval *" ntv ); |
| .fi |
| .SH DESCRIPTION |
| Both of these APIs return information to the caller via the |
| .I ntv |
| argument, a structure of the following type: |
| .PP |
| .in +4n |
| .EX |
| 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 */ |
| }; |
| .EE |
| .in |
| .PP |
| The fields of this structure are as follows: |
| .TP |
| .I time |
| The current time, expressed as a |
| .I timeval |
| structure: |
| .IP |
| .in +4n |
| .EX |
| struct timeval { |
| time_t tv_sec; /* Seconds since the Epoch */ |
| suseconds_t tv_usec; /* Microseconds */ |
| }; |
| .EE |
| .in |
| .TP |
| .I maxerror |
| Maximum error, in microseconds. |
| This value can be initialized by |
| .BR ntp_adjtime (3), |
| and is increased periodically (on Linux: each second), |
| but is clamped to an upper limit (the kernel constant |
| .BR NTP_PHASE_MAX , |
| with a value of 16,000). |
| .TP |
| .I esterror |
| Estimated error, in microseconds. |
| This value can be set via |
| .BR 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. |
| .TP |
| .I tai |
| TAI (Atomic International Time) offset. |
| .PP |
| .BR ntp_gettime () |
| returns an |
| .I ntptimeval |
| structure in which the |
| .IR time , |
| .IR maxerror , |
| and |
| .IR esterror |
| fields are filled in. |
| .PP |
| .BR ntp_gettimex () |
| performs the same task as |
| .BR ntp_gettime (), |
| but also returns information in the |
| .I tai |
| field. |
| .SH RETURN VALUE |
| The return values for |
| .BR ntp_gettime () |
| and |
| .BR ntp_gettimex () |
| are as for |
| .BR adjtimex (2). |
| Given a correct pointer argument, these functions always succeed. |
| .\" FIXME . the info page incorrectly describes the return values. |
| .SH VERSIONS |
| The |
| .BR ntp_gettime () |
| function is available since glibc 2.1. |
| The |
| .BR ntp_gettimex () |
| function is available since glibc 2.12. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .ad l |
| .nh |
| .TS |
| allbox; |
| lbx lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR ntp_gettime (), |
| .BR ntp_gettimex () |
| T} Thread safety MT-Safe |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| .BR ntp_gettime () |
| is described in the NTP Kernel Application Program Interface. |
| .BR ntp_gettimex () |
| is a GNU extension. |
| .SH SEE ALSO |
| .BR adjtimex (2), |
| .BR ntp_adjtime (3), |
| .BR time (7) |
| .PP |
| .ad l |
| .UR http://www.slac.stanford.edu/comp/unix/\:package/\:rtems/\:src/\:ssrlApps/\:ntpNanoclock/\:api.htm |
| NTP "Kernel Application Program Interface" |
| .UE |