That is a horrible, horrible suggestion. It will work fine as long as you get only a few hits a day. But as soon as you get two hits almost simultaneously, you will have problems. If you are lucky, your counter will display a bogus number. If you are unlucky, your visitors will get a broken image icon as the number.

This is a Unix environment. That means, multitasking. It's not a PC, two things can actually happen at the same time! Hence, you need to use critical sections in your code - and lock the file. Here's a suggestion of how to tackle the problem: 

use strict;
use warnings 'all';
use Fcntl qw /:DEFAULT :flock :seek/;

my $counter_file = "/tmp/counter";
 
sysopen my $fh => $counter_file, O_RDWR | O_CREAT, 0644
        or die "Failed to open $counter_file: $!\n";
 
flock    $fh => LOCK_EX   or die "Failed to flock $counter_file: $!\n"
+;
chomp (my $counter = <$fh> || 0);
$counter ++;
seek     $fh => 0, SEEK_SET;
print    $fh "$counter\n" or die "Failed to write to $counter_file: $!
+\n";   
truncate $fh => tell $fh  or die "Failed to truncate $counter_file: $!
+\n";
close    $fh              or die "Failed to close $counter_file: $!\n"
+;
 
... Do whatever you want with $counter here ....

[download]
But this is just shown for educational purposes. Using counters on webpages is so mid-nineties, people have done it before, and there are ready to use programs and modules out there. And I bet Randal has a column about it....

Abigail

In reply to Re: counter by Abigail-II
in thread On server, counter file is read-only by sOKOle

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