ntp_adjtime

NAME

LIBRARY

SYNOPSIS

DESCRIPTION

struct timex { 
	unsigned int modes;	/* clock mode bits (wo) */ 
	long offset;		/* time offset (us) (rw) */ 
	long freq;		/* frequency offset (scaled ppm) (rw) */ 
	long maxerror;		/* maximum error (us) (rw) */ 
	long esterror;		/* estimated error (us) (rw) */ 
	int status;		/* clock status bits (rw) */ 
	long constant;		/* pll time constant (rw) */ 
	long precision;		/* clock precision (us) (ro) */ 
	long tolerance;		/* clock frequency tolerance (scaled 
				 * ppm) (ro) */ 
	/* 
	 * The following read-only structure members are implemented 
	 * only if the PPS signal discipline is configured in the 
	 * kernel. 
	 */ 
	long ppsfreq;		/* pps frequency (scaled ppm) (ro) */ 
	long jitter;		/* pps jitter (us) (ro) */ 
	int shift;		/* interval duration (s) (shift) (ro) */ 
	long stabil;		/* pps stability (scaled ppm) (ro) */ 
	long jitcnt;		/* jitter limit exceeded (ro) */ 
	long calcnt;		/* calibration intervals (ro) */ 
	long errcnt;		/* calibration errors (ro) */ 
	long stbcnt;		/* stability limit exceeded (ro) */ 
};

modes

Defines what settings should be changed with the current ntp_adjtime() call (write-only). Bitwise OR of the following:

offset

Time offset (in microseconds), used by the PLL/FLL to adjust the system time in small increments (read-write).

freq

Frequency offset (scaled ppm) (read-write).

maxerror

Maximum error (in microseconds). Initialized by an ntp_adjtime() call, and increased by the kernel once each second to reflect the maximum error bound growth (read-write).

esterror

Estimated error (in microseconds). Set and read by ntp_adjtime(), but unused by the kernel (read-write).

status

System clock status bits (read-write). Bitwise OR of the following:

constant

PLL time constant, determines the bandwidth, or “stiffness”, of the PLL (read-write).

precision

Clock precision (in microseconds). In most cases the same as the kernel tick variable (see hz(9)). If a precision clock counter or external time-keeping signal is available, it could be much lower (and depend on the state of the signal) (read-only).

tolerance

Maximum frequency error, or tolerance of the CPU clock oscillator (scaled ppm). Ordinarily a property of the architecture, but could change under the influence of external time-keeping signals (read-only).

ppsfreq

PPS frequency offset produced by the frequency median filter (scaled ppm) (read-only).

jitter

PPS jitter measured by the time median filter in microseconds (read-only).

shift

Logarithm to base 2 of the interval duration in seconds (PPS, read-only).

stabil

PPS stability (scaled ppm); dispersion (wander) measured by the frequency median filter (read-only).

jitcnt

Number of seconds that have been discarded because the jitter measured by the time median filter exceeded the limit MAXTIME (PPS, read-only).

calcnt

Count of calibration intervals (PPS, read-only).

errcnt

Number of calibration intervals that have been discarded because the wander exceeded the limit MAXFREQ or where the calibration interval jitter exceeded two ticks (PPS, read-only).

stbcnt

Number of calibration intervals that have been discarded because the frequency wander exceeded the limit MAXFREQ/4 (PPS, read-only).

struct ntptimeval { 
	struct timeval time;	/* current time (ro) */ 
	long maxerror;		/* maximum error (us) (ro) */ 
	long esterror;		/* estimated error (us) (ro) */ 
};

time

Current time (read-only).

maxerror

Maximum error in microseconds (read-only).

esterror

Estimated error in microseconds (read-only).

RETURN VALUES

ERRORS

SEE ALSO

http://www.bipm.fr/enus/5_Scientific/c_time/time_1.html

 

http://www.boulder.nist.gov/timefreq/general/faq.htm

 

ftp://time.nist.gov/pub/leap-seconds.list

 

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