# subroutine name: appenddata
# Appends passed string and newline char ("\n") to specified file
# If error occurs, makes CGI process exit with error
#
# Global variables used:
#	$no_flock - disable flock or not
sub appenddata {
	my($datafile,$row) = @_;

	# If OS (like Win95) desn't support flock, we have to
	# go unreliable and slow way and create "lock" file
	GetFileLock("$datafile.lock");
	my $existed = -e $datafile;
	local *DATA;
	if (open(DATA,">>$datafile")) {
		unless ($no_flock) {
			# Exclusive locking
			flock(DATA, 2) ;
			# In case someone appended while we
			# were waiting, seek to EOF
			seek(DATA, 0, 2);
		}
		print DATA "$row\n";
		# unlock file
		flock(DATA, 8) unless ($no_flock);
		close(DATA);
		chmod(0666, $datafile) unless ($existed);
		ReleaseFileLock("$datafile.lock");
	} else {
		ReleaseFileLock("$datafile.lock");
		die("Error in subroutine appenddata: Can't open $datafile. Reason: $!");
	}
}