Well, to respond to Merlyn, I started thinking about how to do it after reading a reply he wrote on clpm that File::Backwards and Tie::File are good, but not quite the fastest. So I thought, hmmm, how would I do this? The code is the most straight forward approach I could come up with. Just start at the EOF and count back byte by byte, counting newlines, until I satified my $numlines test. I tested it against the following File::Backwards script on a 100 meg file, and my script was faster by a small amount, plus I don't need to use a module. I used the system time command to time them. 
#!/usr/bin/perl
use File::ReadBackwards;
#usage tailfilebackwards filename numlines 
my $filename = shift or die "Usage: $0 file numlines\n";
my $numlines  = shift;

$bw = File::ReadBackwards->new($filename) or
die "can't read $filename $!" ;

$count=0;
while(defined($line = $bw->readline)){
push @lines,$line ;
$count++;
if ($count == $numlines){last}
}
@lines= reverse @lines;
print "@lines\n";
exit;

[download]
My sample times follow: 
For 3 tries -> time tailfilebackwards ARCHIVE 10
real    0m0.078s
user    0m0.040s
sys     0m0.010s

real    0m0.060s
user    0m0.040s
sys     0m0.010s

real    0m0.077s
user    0m0.040s
sys     0m0.000s
###########################################################
For 3 tries -> time tailz ARCHIVE 10

real    0m0.051s
user    0m0.010s
sys     0m0.000s

real    0m0.056s
user    0m0.010s
sys     0m0.010s

real    0m0.056s
user    0m0.010s
sys     0m0.020s
##########################################################
Now I admit that my method is non-portable, so the modular methods are better in that respect, but time-wise they are not. If anyone cares to comment on how I might make my method better, I would appreciate that.

In reply to Re: pure perl tail by zentara
in thread pure perl tail by zentara

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