Hello jayu_rao,

First, if this code:

my $TIMESTAMP;
...
for (@dates) {
     $TIMESTAMP = $_->[0]->strftime("%Y-%m-%d %R");
}
[download]

does what I think it does, it can be written more simply and efficiently without the loop:

my $TIMESTAMP = $dates[-1][0]->strftime("%Y-%m-%d %R");
[download]

Update: Changed $dates[-1]->strftime to $dates[-1][0]->strftime.

Now, let’s look at your second challenge:

The 2nd log file may not have the exact timestamp (in the seconds field) as in log1 file.

You don’t say where the strftime method comes from, but if it follows the same conventions as the POSIX::strftime::GNU module, then the %R conversion specification produces “[t]he time in 24-hour notation (%H:%M)” only — so $TIMESTAMP is guaranteed not to contain seconds. (If you want seconds, you have to use %T.)

Now to the first challenge. Try something like this:

my @log_final;
my $last = 0;

while (my $log_line = $log_bckwards->readline) {
    if ($log_line =~ /$TIMESTAMP/) {
        $last = 1;
    }
    elsif ($last) {
        last;
    }
    unshift @log_final, $log_line;
}
[download]

Note that in the code you have shown, the capture and /g modifier in your regex do nothing.

Hope that helps,

I think the OP wanted all lines before the last instance of the TIMESTAMP match, including non-matching ones.

Better maybe as:

my @log_final;
my $watching_for_last_match = 0;
#  ^ Bonus! This var will give a count of 
#    entries within the timestamp at the end,
#    compare with scalar(@log_final) for stats

while (my $log_line = $log_bckwards->readline) {
  if ( $watching_for_last_match ) {    
    if ($log_line !~ /$TIMESTAMP/) {
      last;
    }
  } else {
    if ($log_line =~ /$TIMESTAMP/) {
      $watching_for_last_match++;
    }
  }        
  unshift @log_final, $log_line;
}
[download]

Remember: Ne dederis in spiritu molere illegitimi!

Hello 1nickt,

I think the OP wanted all lines before the last instance of the TIMESTAMP match, including non-matching ones.

Yes, exactly, although since we are reading the file backwards, we should perhaps say: all lines from the first TIMESTAMP match (inclusive) to the end of the file.

Leaving aside the added line count, it seems to me that your code is logically identical to mine. Am I missing something?

---

But in reading your post it occurs to me that there is a logic error in both of our approaches: what if the TIMESTAMP never has an exact match? The OP is, apparently, confident that there will always be a match, but a more robust design would allow for the possibility that there may not be:

my @log_final;

while (my $log_line = $log_bckwards->readline) {
    my $current_timestamp = extract_timestamp($log_line);
    last if compare_timestamps($current_timestamp, $TIMESTAMP) < 0;
    unshift @log_final, $log_line;
}
[download]

— with the implementation of extract_timestamp() and compare_timestamps() being left as the proverbial exercise for the reader. :-)

Hope that helps,

Athanasius <°(((>< contra mundum

Iustus alius egestas vitae, eros Piratica,