# fopen: opens a file. Allows for file locking and better error-handling.
	sub fopen ($$;$) {
		my ($pack, $file, $line) = caller;
		$file_open++;
		my ($filehandle, $filename, $usetmp) = @_;
		## make life easier - spot a file that's not closed!
		if (($debug == 1 or ($debug == 2 && $iamadmin))) { $openfiles .= qq~$filehandle -> $filename ~; }
		my ($flockCorrected, $cmdResult, $openMode, $openSig);

		$serveros = "$^O";
		if ($serveros =~ m/Win/ && substr($filename, 1, 1) eq ":") {
			$filename =~ s~\\~\\\\~g;    # Translate windows-style \ slashes to windows-style \\ escaped slashes.
			$filename =~ s~/~\\\\~g;     # Translate unix-style / slashes to windows-style \\ escaped slashes.
		} else {
			$filename =~ tr~\\~/~;       # Translate windows-style \ slashes to unix-style / slashes.
		}
		$LOCK_EX     = 2;                # You can probably keep this as it is set now.
		$LOCK_UN     = 8;                # You can probably keep this as it is set now.
		$LOCK_SH     = 1;                # You can probably keep this as it is set now.
		$usetempfile = 0;                # Write to a temporary file when updating large files.

		# Check whether we want write, append, or read.
		$filename =~ m~\A([<>+]*)(.+)~;
		$openSig  = $1                    || '';
		$filename = $2                    || $filename;
		$openMode = $yyOpenMode{$openSig} || 0;

		$filename =~ s~[^/\\0-9A-Za-z#%+\,\-\ \.\:@^_]~~g;    # Remove all inappropriate characters.

		if ($filename =~ m~/\.\./~) { &fatal_error("cannot_open","$filename. $maintxt{'609'}"); }

		# If the file doesn't exist, but a backup does, rename the backup to the filename
		if (!-e $filename && -e "$filename.bak") { rename("$filename.bak", "$filename"); }
		if (-z $filename && -e "$filename.bak") { rename("$filename.bak", "$filename"); }

		$testfile = $filename;
		if ($use_flock == 2 && $openMode) {
			my $count;
			while ($count < 15) {
				if (-e $filehandle) { sleep 2; }
				else { last; }
				++$count;
			}
			unlink($filehandle) if ($count == 15);
			local *LFH;
			CORE::open(LFH, ">$filehandle");
			$yyLckFile{$filehandle} = *LFH;
		}

		if ($use_flock && $openMode == 1 && $usetmp && $usetempfile && -e $filename) {
			$yyTmpFile{$filehandle} = $filename;
			$filename .= '.tmp';
		}

		if ($openMode > 2) {
			if ($openMode == 5) { $cmdResult = CORE::open($filehandle, "+>>$filename"); }
			elsif ($use_flock == 1) {
				if ($openMode == 4) {
					if (-e $filename) {

						# We are opening for output and file locking is enabled...
						# read-open() the file rather than write-open()ing it.
						# This is to prevent open() from clobbering the file before
						# checking if it is locked.
						$flockCorrected = 1;
						$cmdResult = CORE::open($filehandle, "+<$filename");
					} else {
						$cmdResult = CORE::open($filehandle, "+>$filename");
					}
				} else {
					$cmdResult = CORE::open($filehandle, "+<$filename");
				}
			} elsif ($openMode == 4) {
				$cmdResult = CORE::open($filehandle, "+>$filename");
			} else {
				$cmdResult = CORE::open($filehandle, "+<$filename");
			}
		} elsif ($openMode == 1 && $use_flock == 1) {
			if (-e $filename) {

				# We are opening for output and file locking is enabled...
				# read-open() the file rather than write-open()ing it.
				# This is to prevent open() from clobbering the file before
				# checking if it is locked.
				$flockCorrected = 1;
				$cmdResult = CORE::open($filehandle, "+<$filename");
			} else {
				$cmdResult = CORE::open($filehandle, ">$filename");
			}
		} elsif ($openMode == 1) {
			$cmdResult = CORE::open($filehandle, ">$filename");    # Open the file for writing
		} elsif ($openMode == 2) {
			$cmdResult = CORE::open($filehandle, ">>$filename");    # Open the file for append
		} elsif ($openMode == 0) {
			$cmdResult = CORE::open($filehandle, $filename);        # Open the file for input
		}
		unless ($cmdResult)      { return 0; }
		if     ($flockCorrected) {

			# The file was read-open()ed earlier, and we have now verified an exclusive lock.
			# We shall now clobber it.
			flock($filehandle, $LOCK_EX);
			if ($faketruncation) {
				CORE::open(OFH, ">$filename");
				unless ($cmdResult) { return 0; }
				print OFH '';
				CORE::close(OFH);
			} else {
				truncate(*$filehandle, 0) || &fatal_error("truncation_error","$filename");
			}
			seek($filehandle, 0, 0);
		} elsif ($use_flock == 1) {
			if ($openMode) { flock($filehandle, $LOCK_EX); }
			else { flock($filehandle, $LOCK_SH); }
		}
		return 1;
	}