I have done some rather benchmarking of "line at a time" vs. "chunk at a time with manual split into lines" vs. "line at a time w/ lots of buffering". "block at a time with manual split into lines" is clearly the fastest by almost 2 to 1 over the other 2 methods. I've included my benchmarking program and results below: 
Benchmark: running BufferedFileHandle, chunk, linebyline, each for at 
+least 3 CP
U seconds...
BufferedFileHandle:  3 wallclock secs ( 3.22 usr +  0.08 sys =  3.30 C
+PU) @  <b>2.73/s</b> (n=9)
     chunk:  4 wallclock secs ( 2.89 usr +  0.32 sys =  3.21 CPU) @  <
+b>4.36/s</b> (n=14)
linebyline:  4 wallclock secs ( 3.25 usr +  0.06 sys =  3.31 CPU) @  <
+b>2.72/s</b> (n=9)

[download]
#!/usr/bin/perl

use Benchmark;
use strict;
use FileHandle;

timethese(0, { 'linebyline' => \&linebyline, 
               'chunk' => \&chunk ,
               'BufferedFileHandle' => \&BufferedFileHandle });

sub linebyline {
  open(FILE, "file");
  while(<FILE>) { }
  close(FILE);
}

sub chunk {
  my($buf, $leftover, @lines);
  open(FILE, "file");
  while(read FILE, $buf, 64*1024) {
    $buf = $leftover.$buf;
    @lines = split(/\n/, $buf);
    $leftover = ($buf !~ /\n$/) ? pop @lines : "";
    foreach (@lines) { }
 }
 close(FILE);
}

sub BufferedFileHandle{
  my $fh=new FileHandle;
  my $buffer_var;
  $fh->open("file");
  $fh->setvbuf($buffer_var, _IOLBF, 64*1024);
  while(<$fh>) { }
  close(FILE);
}

[download]
I'd be very interested to see your results that show diffrently.

Edit to replace CODE tags for PRE tags around long lines

In reply to RE: RE: RE (tilly) 2 (blame): File reading efficiency and other surly remarks by lhoward
in thread File reading efficiency and other surly remarks by Hot Pastrami

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