sysopen(LOG_FILE, $logfile, O_RDWR|O_CREAT ) or die "Can't opne $logfile: $!";  #mit lese/schreibrechten öffnen, ggf neu anlegen
if (flock(LOG_FILE, &LOCK_EX)) {         # exclusive lock
    while (<LOG_FILE>) {
	      print LOG_FILE $_;
    }
    flock(LOG_FILE, &LOCK_UN) or die "Can't unlock logfile $!"; # unlock
}
close(LOG_FILE) or die "Can't close logfile $!";