while (<FILE>){};
print "length = $.";

##</code><code>##

#!/usr/bin/perl

use warnings;
use strict;

use Benchmark;

timethese(100, {
        'line_by_line' => q{
                open(INFILE,'test.dat') or die "open: $!";
                while(<INFILE>){};
                close(INFILE);
        },
        'chunk' => q{
                $count = 0;
                open(INFILE,'test.dat') or die "open: $!";
                local $/=\1024000;
                while(<INFILE>) { $count += tr/\n// }
                close(INFILE);
        }
});

##</code><code>##

Benchmark: timing 100 iterations of chunk, line_by_line...
     chunk:  3 wallclock secs ( 1.58 usr +  0.70 sys =  2.28 CPU) @ 43.80/s (n=100)
     line_by_line: 12 wallclock secs ( 9.54 usr +  0.72 sys = 10.27 CPU) @  9.74/s (n=100)

##</code><code>##

open INFILE,'test.dat' or die "open: $!";
my $count = 0;
while (sysread(INFILE,$_,102400)) { $count += tr/\n//; }

##</code><code>##

/home/rhet/misc> ./testfcount.pl
Benchmark: timing 100 iterations of chunk, line_by_line, sysread...
     chunk: 12 wallclock secs ( 8.00 usr +  3.52 sys = 11.53 CPU) @  8.68/s (n=100)
     line_by_line: 154 wallclock secs (149.20 usr +  3.29 sys = 152.50 CPU) @  0.66/s (n=100)
     sysread:  6 wallclock secs ( 4.09 usr +  1.62 sys =  5.71 CPU) @ 17.52/s (n=100)