Re: while loop acting up, though I'm not sure how

[Athanasius]

Hello msh210,

The logic of your while loop condition is too complicated. Rearranging and simplifying, I came up with this, which seems to do what you want:

#! perl
use strict;
use warnings;

use constant
{
    DELAY  =>   10,
    EXPIRY => 3600,
    MARGIN =>  300,
};

my $time   =  time;
my $expiry = $time + EXPIRY;

while ($time + MARGIN < $expiry)
{
    my $previoustime = $time;
    warn $time;

    sleep DELAY + $previoustime - $time
        unless $time - $previoustime >= DELAY;

    $time = time;
}

Output:

16:17 >perl 1453_SoPW.pl
1447741073 at 1453_SoPW.pl line 18.
1447741083 at 1453_SoPW.pl line 18.
1447741093 at 1453_SoPW.pl line 18.
1447741103 at 1453_SoPW.pl line 18.
1447741113 at 1453_SoPW.pl line 18.
...

A side note: sleep returns the number of seconds slept (as an integer). So the condition:

( $time - $previoustime >= 10
  or sleep (10 + $previoustime - $time)
)

could evaluate to zero — which is false — causing the loop to terminate prematurely. In my testing I don’t see this happening, but it’s still a logic error (a potential bug), and so a further reason to simplify the logic of the loop condition.

Hope that helps,