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Re: [gpsd-dev] A detail in your ntpoffset script


From: Andy Walls
Subject: Re: [gpsd-dev] A detail in your ntpoffset script
Date: Tue, 22 Oct 2013 18:24:51 -0400
User-agent: K-9 Mail for Android

A script should really be written that computes the fudge for all the individual refclocks present in the file: 127.127.d.u for drivers d, units u.

It would nice if it could skip the first n seconds as well. to throw out the startup transient. The transient values can be very far from the stable average.

You might need perl vs awk for all that. (gaunlet thrown down :) )

Regards,
Andy

address@hidden wrote:
awk '
/127\.127\.28\.0/ { sum += $5 * 1000; cnt++; }
END { print sum / cnt; }
' </var/log/ntpstats/peerstats

Should that be .1 rather than .0?

I'm thinking of this coment in ntpshm.c:

* Segments 0 and 1: permissions 0600, i.e. other programs can only
* read and write as root.
*
* Segments 2 and 3: permissions 0666, i.e. other programs can read
* and write as any user. I.e.: if ntpd has been
* configured to use these segments, any
* unpriviliged user is allowed to provide data
* for synchronisation.
*
* As gpsd can be started as both root and non-root, this behaviour is
* mimicked by:
*
* Started as root: do as ntpd when attaching (creating) the segments.
* (In contrast to ntpd, which only attaches (creates) configured
* segments, gpsd creates all segments.)
*
* Started as non-root: only attach (create) segments 2 and 3 with
* permissions 0666. As the permissions are for any user, the creator
* does not matter.
*
* For each GPS module gpsd controls, it will use the attached ntpshm
* segments in pairs (for coarse clock and pps source, respectively)
* starting from the first found segments. I.e. started as root, one
* GPS will deliver data on segments 0 and 1, and as non-root data
* will be delivered on segments 2 and 3.

This seems to imply that the PPS unit is .1 rather than .0.

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