Last week the US and Canada changed to Daylight Savings Time.
Usually, I set my wristwatch from my computer (which uses NTP)
then wander around the house resetting all the clocks, correcting any
drift accumulated over the last 6 months.
This year I thought it would make more sense to use my tablet, which uses
NTP directly. Normally I type "date" in an xterm. Then I was thinking
"what if it says 09:04:03 when it's really 09:04:03.99 ?". (which the GUI
clock apps presumably handle).
Then "Can I display better than 1 second accuracy ?"
So, after rejecting a version that just sat in a tight loop, I have one
that microsleeps until the next 1/10th second.
#!/usr/bin/perl
use Time::HiRes qw( gettimeofday usleep ) ;
$| = 1 ;
system("ntptrace -n -m 1"); # check accuracy before starting
while (1) {
$t = gettimeofday() ;
$t2 = $t * 10 ;
$it = 1 + int($t2) - $t2 ; # time left till next tick
($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime($t);
$dsec = $sec + $t-int($t) ;
printf("%2.2d:%2.2d:%04.1f\r",$hour,$min,$dsec) ;
$dt = usleep ($it*100000) ;
}
I can't remember where ntpdate came from. One of the repositories, I
think. ntptrace is written in Perl and was missing Getopt/Std.pm
out-of-the-box. I found it in scratchbox and copied it across.
Also Time/HiRes.pm, Time/HiRes/HiRes.so.
/etc/ntp.conf seemed to be missing from ntpdate, and I think needs to be
set for ntpd to lock (unless it can find a multicast stream, maybe).
I have
driftfile /var/lib/ntp/drift
server 0.ca.pool.ntp.org dynamic
server 1.ca.pool.ntp.org dynamic
Maybe this has all been done before in a nice GUI. I didn't look;
simple things I find it easier to just script.
It also works as a kind of split timer - hitting "return" when it's
running leaves the time on the previous line.
--
Andrew Daviel, TRIUMF, Canada
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