Add Lua script to handle DOS and UNIX line ending issues

This script converts file line endings to CRLF while preserving shebang compatibility across systems. It ensures the first line with a shebang is properly formatted for UNIX execution while maintaining readability in DOS/Windows. The tool facilitates smoother file handling between platforms.

Author: Lethja

demo/extra/dosfren.lua

@@ -0,0 +1,65 @@
+#!/usr/bin/env lua
+
+
+--[[
+	DOS and UNIX disagree on what a new line should be
+	DOS says it's a carriage return followed by a line feed (CRLF)
+	while UNIX says it's just a line feed on its own (LF).
+	Many tools (Lua included) don't care while others like
+	`TYPE` in DOS and Notepad in Windows will not display correctly.
+	Tools like unix2dos/dos2unix exist convert line endings between the systems,
+	however, in doing so, the CR in CRLF on the shebang line might be
+	interpreted literally and prevent correct execution on UNIX systems.
+
+	This script named "DOS friend" will convert every line ending of the files
+	passed to it with CRLF with the exception of the first line when a shebang
+	is present. When this occurs, the line will instead write LFCRLF so that
+	both types of systems can pleasantly read and run the file.
+--]]
+
+LF = string.char(0x0A)
+CRLF = string.char(0x0D) .. LF
+
+local function Shebang(inFile)
+	inFile:seek("set", 0)
+	local line1 = inFile:read("*l")
+	if line1:match("^#!") then
+		return line1 .. LF .. CRLF
+	end
+	return nil
+end
+
+if #arg < 1 then
+	print(arg[-1] .. " " .. arg[0] .. " [FILE]...")
+	os.exit(1)
+end
+
+for i = 1, #arg do
+	local inFile, err = io.open(arg[i])
+	if not inFile then print(arg[i] .. ": " .. err) else
+		local outFile
+		outFile, err = io.open(arg[i] .. ".tmp", "wb")
+		if not outFile then
+			print(arg[i] .. ".tmp: " .. err)
+		else
+			local shebang = Shebang(inFile)
+			if shebang then
+				outFile:write(shebang)
+				while true do
+					local line = inFile:read("*l")
+					if line then
+						outFile:write(line .. CRLF)
+					else
+						break
+					end
+				end
+				inFile:close() outFile:close()
+				os.remove(arg[i])
+				os.rename(arg[i] .. ".tmp", arg[i])
+			else
+				inFile:close() outFile:close()
+				os.remove(arg[i] .. ".tmp")
+			end
+		end
+	end
+end