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Comparing timestamps that are in 2 different but defined styles

by technojosh (Priest)
on Jul 23, 2010 at 20:03 UTC ( #851089=perlquestion: print w/ replies, xml ) Need Help??
technojosh has asked for the wisdom of the Perl Monks concerning the following question:

I have the following problem, and I've put *a little* thought and search into the solution but nothing is smacking me in the face just yet:

I maintain an automated test tool that validates a web app sitting on a MSSQL db. We have added a set of 'audit' tables to our MSSQL database, and these tables all have 'DateTime' columns, which give dates in the format:

2010-07-23 19:44:43.523

I need to compare that date with Perl's localtime(time) value, and decide if this stamp is within ~1 minute of the value stored in the database.

FYI: on my system (windows7), localtime(time) returns the following format:

perl -e "print localtime(time).$/" Fri Jul 23 14:57:39 2010

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Re: Comparing timestamps that are in 2 different but defined styles
by Corion (Pope) on Jul 23, 2010 at 20:08 UTC

    Maybe you want to bring both timestamps into the same format, and then compare them? See POSIX::strftime, and localtime.

Re: Comparing timestamps that are in 2 different but defined styles
by JediWizard (Deacon) on Jul 23, 2010 at 20:31 UTC

    There are also a number of CPAN modules that can parse and reformat date/timestamps into a common format. Date::Manip I belive also has date comparison functions.


    They say that time changes things, but you actually have to change them yourself.

    —Andy Warhol

Re: Comparing timestamps that are in 2 different but defined styles
by thunders (Priest) on Jul 23, 2010 at 21:52 UTC

    POSIX::strptime look promising. Something like this (untested)

    use POSIX::strptime; my $timestamp = "2010-07-23 19:44:43.523"; #remove milliseconds $timestamp =~ s/\.\d+$//; my ($t_sec, $t_min, $t_hour, $t_mday, $t_mon, $t_year, $t_wday, $t_yda +y) = POSIX::strptime($timestamp, "%Y-%m-%d %H:%M:%S"); my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime(time); if($t_year == $year && $t_mon == $mon && $t_mday == $mday && $t_hour == $hour && abs($t_min-$min) <= 1){ #dates match }
      if($t_year == $year && $t_mon == $mon && $t_mday == $mday && $t_hour == $hour && abs($t_min-$min) <= 1){ ... }

      How about ten seconds before the hour/day/etc versus ten seconds after: Are these two times within 60 seconds of each other per this test?

      Concept is great, but OP just has to be careful when implementing it, as edge conditions always bite us. 8:59:01 compared to 9:00:00 is less than a minute to my eye, but wouldn't pass the generally correct test.

      Similar problem with 9:00:59 and 9:01:01, when you're comparing seconds ...

      Doh, good point guys. I wasn't thinking.

      Here's another option: turn the values returned by POSIX::strptime into a UNIX epoch with Time::Local, then subtracting that from the value given by time() and seeing if abs($diff) < 60.

Re: Comparing timestamps that are in 2 different but defined styles
by JavaFan (Canon) on Jul 23, 2010 at 23:38 UTC
    Why not have the database do the comparison?
Re: Comparing timestamps that are in 2 different but defined styles
by kp2a (Sexton) on Jul 24, 2010 at 01:36 UTC
    Date::Manip understands just about any format and computes just about any way you like. I have used it for a decade!
Re: Comparing timestamps that are in 2 different but defined styles
by intel (Beadle) on Jul 24, 2010 at 15:41 UTC

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