Just a quick benchmark. I've used both of merlyn's variations on readdir and thrown in glob as well (just for giggles, as is shown in the benchmark results). Here's the code: 
#!/usr/local/bin/perl -w
use strict;
use Benchmark qw(:all);
my $dir="/home/bv/tmp/testdir";
cmpthese('1000', { 'merlyn_1' => \&merlyn1,
                   'merlyn_2' => \&merlyn2,
                   'glob' => \&glob,
                 } );
sub merlyn1 {
  opendir D, $dir or die;
  my $count = () = readdir D;
  $count -= 2; # :-)
  closedir D;
}
sub merlyn2 {
  opendir D, $dir or die;
  my $count = -2;
  $count++ while readdir D;
  closedir D;
}
sub glob {
  my $count = () = glob ("$dir/*");
  $count += () = glob ("$dir/.[^.]*");
  $count-=2; 
}

[download]
With 255 (empty) files, this is the result: 
Benchmark: timing 1000 iterations of glob, merlyn_1, merlyn_2...
      glob:  6 wallclock secs ( 4.55 usr +  1.55 sys =  6.10 CPU) @ 16
+3.93/s (n=1000)
  merlyn_1:  1 wallclock secs ( 0.37 usr +  0.13 sys =  0.50 CPU) @ 20
+00.00/s (n=1000)
  merlyn_2:  1 wallclock secs ( 0.47 usr +  0.17 sys =  0.64 CPU) @ 15
+62.50/s (n=1000)
           Rate     glob merlyn_2 merlyn_1
glob      164/s       --     -90%     -92%
merlyn_2 1562/s     853%       --     -22%
merlyn_1 2000/s    1120%      28%       --

[download]
That's clear. Glob is very much out of the picture, while merlyn_1 is about a fifth to a quarter faster again than merlyn_2.

Let's try 1024 files: 

           Rate     glob merlyn_2 merlyn_1
glob     37.0/s       --     -91%     -93%
merlyn_2  400/s     982%       --     -22%
merlyn_1  513/s    1287%      28%       --

[download]
Same result. merlyn_1 is the clear winner! I'm guessing that this is because we are not doing an increment to $count after every file, but that's just a wild guess.

Update: For some extra giggles, here's the result for 10K files: 

           Rate     glob merlyn_2 merlyn_1
glob     3.04/s       --     -92%     -93%
merlyn_2 38.0/s    1150%       --      -7%
merlyn_1 40.7/s    1242%       7%       --

[download]

CU
Robartes-

In reply to Re: Quickest, most efficient way to get number of files in dir? by robartes
in thread Quickest, most efficient way to get number of files in dir? by Anonymous Monk

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