#!/usr/bin/perl

use warnings;
use strict;
use Fcntl;
my $pidFile    = "C:/xampp/cgi-bin/raumverw_2.pid";

&CheckAllReadyRunning;

sub CheckAllReadyRunning {
#LOCK_SH = 1;
my $LOCK_EX = 2;
my $LOCK_NB = 4;
my $LOCK_UN = 8;

if( ! open( pidHdl, ">>$pidFile"))
{
    flock( pidHdl, $LOCK_UN);
    close( pidHdl);
    die;
}
if( ! flock( pidHdl, $LOCK_NB + $LOCK_EX))
{
    flock( pidHdl, $LOCK_UN);
    close( pidHdl);
    die;
}
truncate( pidHdl, 0);
select( pidHdl); $| = 1; select( STDOUT);
print( pidHdl "$$");
};