#!/usr/bin/perl -wT

use CGI qw( :all );
use strict;

$|++;

print header(),
      start_html( "Counter Test" );

# *snip*

my $datapath = "/home/username/data/project";  # outside httpd directory
my $datafile = "$datapath/counter.dat";        # Permissions: 666
my $subID    = sprintf( "%06d", getNewCounter( $datafile ) );

# more snipped, including code verification of directory, file, and attributes.

print "Get Counter Results: $subID",
      end_html;
      

sub getNewCounter
# ---------------------------------------------------------------
# Reads and incremements the counter value.  
# Credit: Implementation based on sample found in the perl CGI
# FAQ at www.perl.com.
# ---------------------------------------------------------------
{
   my( $countfile ) = @_;

   open( FILE, "$countfile" )  or die "Cannot open counter for reading.\n";
   flock( FILE, 2 )            or die "Cannot lock counter for reading.\n";

   my( $countval ) = <FILE>;
   chomp( $countval );  

   flock( FILE, 8 )            or die "Cannot unlock counter after reading.\n";
   close( FILE )               or die "Cannot close counter after reading.\n";
 
   open( FILE, ">$countfile" ) or die "Cannot open counter for writing.\n";
   flock( FILE, 2 )            or die "Cannot lock counter for writing.\n";
 
   print FILE ++$countval;

   flock( FILE, 8 )            or die "Cannot unlock counter after writing.\n";
   close( FILE )               or die "Cannot close counter after writing.\n";
   return( $countval )

}