#!/usr/bin/perl
use Fcntl;

$| = 1;
print "Content-type: text/html\n\n";

# open counter file & establish lock
sysopen(FH, "count.log", O_RDWR|O_CREAT) or die "can't open numfile: $!";
flock(FH, 2) or die "can't flock numfile: $!";

# retrieve current count
$num = <FH> || 0;
seek(FH, 0, 0) or die "can't rewind numfile: $!";
truncate(FH, 0) or die "can't truncate numfile: $!";

#increment counter
$num ++;
(print FH $num, "\n") or die "can't write numfile: $!";

# close counter file (implies unlock)
close FH or die "can't close numfile: $!";  

# display count
print "<H1>$num</H1>";