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Re: working with time ranges that cross days
by shmem (Chancellor) on Jan 31, 2007 at 15:17 UTC
    Work harder :-)

    The localtime function is what you look for.

    --shmem 

    _($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}
[reply]
      FWIW, just want to elaborate on and correct the above tip a bit. Basically, it suggested to convert your Date/Time representation of both ends of your range to unix time (number of seconds since the Epoch). This will give you two integers, each uniquely identifying point in time, to work with. To achieve this you should NOT use localtime as suggested but a core module Time::Local and its timelocal function.

      BR

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[d/l]
        Your reply must have been aimed at another node.
        I didn't suggest any conversion whatsoever.

        --shmem 

        _($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}
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Re: working with time ranges that cross days
by graff (Chancellor) on Feb 01, 2007 at 04:12 UTC
    Can someone please tell me the best (most efficient) way for setting a night time period to be between 8:30pm and 7am and then detecting when the program in question is running at night time.

    Do you mean: "How can a perl program detect that it is running between 8:30pm and 7am local time?" If that's the question, one answer would be a subroutine like the following. I've decided to set it up as a subroutine because that makes it easier to parameterize the conditions -- who knows, next week you might want a program to check whether it's running between 9:45am and 11:53am... 

    use POSIX;
sub timenow_is_between
{
    my ( $bgn, $end ) = @_;  # args are "HH:MM" strings (length==5)
                             #  e.g. 20:30 or 07:00
    my $timenow = strftime( "%H:%M", localtime );
    if ( $bgn ge $end ) {
        return ( $timenow ge $bgn or $timenow lt $end );
    } else {
        return ( $timenow ge $bgn and $timenow lt $end );
    }
}

    [download]
    (Update: decided to use "ge" instead of "gt" when testing $bgn against $end, and when testing $timenow against $bgn; this should "do the right thing" in various boundary conditions, like $bgn and $end being identical, or different by just one minute.)

    Here's an example of how you would use it: 

    if ( timenow_is_between( "20:30", "07:00" ) {
    print "this program is running at night\n";
} else {
    print "it is not night time right now\n";
}

    [download]
    But having seen the longer snippets of code you posted in a couple of your replies on this thread, it's not clear to me what your goal really is (and I wonder whether you have a clear idea of what your goal really is).

    Note that POSIX (which provides the "strftime" function) is a "core" module -- it's available for use in any standard perl installation.

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