ntp_gettime(2)ntp_gettime(2)NAMEntp_gettime - Get the date, time, and kernel time error values
SYNOPSIS
#include <sys/timex.h>
int ntp_gettime(
struct ntptimeval *tp );
PARAMETERS
Points to the ntptimeval structure in which information is returned.
The ntptimeval structure is described in the <sys/timex.h> header file.
DESCRIPTION
The ntp_gettime() system call returns three read-only values in the
ntptimeval structure. The ntptimeval structure members are as follows:
The current system time expressed as a Unix timeval structure. The
timeval structure consists of two 32-bit words: the first is the number
of seconds past 1 January 1970, assuming no intervening leap-second
insertions or deletions; and the second is the number of microseconds
within the second. The value of the time_maxerror kernel variable,
which represents the maximum error of the indicated time relative to
the primary synchronization source, in microseconds. For NTP, the value
is initialized to the synchronization distance, which is equal to the
root dispersion plus one-half the root delay. It is increased by a
small amount (time_tolerance) each second to reflect the maximum clock
frequency error. This variable is modified by the kernel, but is other‐
wise not used by the kernel. The value of the time_esterror kernel
variable, which represents the expected error of the indicated time
relative to the primary synchronization source, in microseconds. For
NTP, the value is determined as the root dispersion, which represents
the best estimate of the actual error of the system clock based on its
past behavior, together with observations of multiple clocks within the
peer group. This variable is not used by the kernel.
RETURN VALUES
Upon successful completion, a value of 0 (zero) is returned. Otherwise,
a value of -1 is returned and errno is set to indicate the error.
ERRORS
If the ntp_gettime() function fails, errno may be set to one of the
following values: The tp parameter points to a location outside of the
allocated address space of the process. The kernel was configured
without the NTP_TIME option.
ntp_gettime(2)
