#!/usr/bin/perl -Tw
# [MJS 25 Sep 2001] A safe web-counter example.
#
# $Id: example-webpage-counter,v 1.1 2003/05/02 11:36:25 suter Exp $

use strict;
use Fcntl qw(:DEFAULT :flock);

# Location of data file.
my $counter = "/tmp/full-path-to-datafile-for-counter";

sysopen(FH, $counter, O_RDWR | O_CREAT) or die "can't open $counter: $!";
my $ofh = select(FH); $| = 1; select($ofh);
flock(FH, LOCK_EX) or die "can't write-lock $counter: $!";
my $number = <FH> || 0;
seek(FH, 0, 0) or die "can't rewind $counter : $!";
print FH $number + 1, "\n" or die "can't write $counter: $!";
truncate(FH, tell(FH)) or die "can't truncate $counter: $!";
close(FH) or die "can't close $counter: $!";

print "Content-Type: text/html\n\n$number";