Hi all,
I am having some trouble with time functions in Perl that correct their
reading for the appropriate timezone. I have minimized my problem into
the example script at the bottom of this message, where:
1. I print a microsecond resolution timestamp for the current time;
2. I read the current timestamp into a variable to be able to
subtract it from later readings, effectively zeroing the timestamp;
3. I read the current timestamp and subtract the pointer from (2),
then print the resulting timestamp.
I expect that the timestamp (3) will be pretty close to 00:00:00.000000,
but rather than that it is an hour off! This has probably to do with the
timezone, that is why I included the date command.
===[ The output ]=========
14:00:28.282859
Sat Oct 2 14:00:28 CEST 2010
01:00:00.290085
==========================
Here is the question. What should I do to get a correct and current
timestamp (1) until the reference time pointer is set (2) AND from that
point onwards timestamps to start from 0:00:00.000000 (3).
For those who are curious what I am trying to accomplish, please refer
to my wiki page on a perl script to interface with the Velleman DVM2000
digital multimeter:
http://wirespeed.xs4all.nl/mediawiki/index.php/Velleman_DVM2000_PCLink
The script continuously prints current time and measured value, and when
a SIGUSR1 is issued to the script, the time stamp must be zero'd.
Thanks!
===[ The script ]=========
#!/usr/bin/perl
use warnings;
use strict;
use Time::HiRes qw(gettimeofday);
my ( $seconds, $usec, $sec, $min, $hour, $day, $month, $year );
my $time_pointer = 0;
# (1) Print a current microsecond timestamp
( $seconds, $usec ) = gettimeofday();
( $sec, $min, $hour ) = localtime( $seconds + $usec / 1000000 -
$time_pointer );
printf "%02d:%02d:%02d.%06d\n", $hour, $min, $sec, $usec;
# Print current system date and time
print `date`;
# (2) The current time in microsecond resolution
( $seconds, $usec ) = gettimeofday();
$time_pointer = $seconds + $usec / 1000000;
# Print a reset'd microsecond timestamp
( $seconds, $usec ) = gettimeofday();
( $sec, $min, $hour ) = localtime( $seconds + $usec / 1000000 -
$time_pointer );
printf "%02d:%02d:%02d.%06d\n", $hour, $min, $sec, $usec;
==========================
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