Hello ukhare,

What have you tried so far, and how has it fallen short of your requirements?

I think the basic algorithm is quite straightforward:

1. Keeping track of the next expected timestamp, read through the file line by line:
2. When the timestamp read is as expected, save the current line (unchanged) in an array;
3. When the timestamp is not as expected, construct the missing line from the current date, the expected timestamp, and 6 nulls, and add it onto the array.
4. After each line, update the expected timestamp by 10 minutes.
5. When finished, rename the input file as a backup,
6. and then overwrite the input file with the array of lines accumulated in steps 1 to 4 above.

The only tricky part is incrementing the timestamp. Here is one approach:

sub inc
{
    my ($next) = @_;

    my ($hours, $mins, $secs) = split /:/, $next;
    $mins += 10;

    if ($mins >= 60)
    {
        ++$hours;
        $mins -= 60;
    }

    return sprintf '%02d:%02d:%02d', $hours, $mins, $secs;
}
[download]

which you would call like this:

$next = inc($next);
[download]

Update: Changed $mins = 0; to $mins -= 60; to allow for the possibility that minutes are not multiples of 10.

Hope that helps,