-- Select the files you want to change content
replace_file =  {
                            "e:/test/toto.conf",
                            "e:/test/titi.conf",
                        }

-- Select the string you want to replace in bracket by the string after the equal
replace_string = {
                            ["toto"] = "titi",
                            ["titi"] = "tata",
                         }

-- Put "\n" for unix, "\r\n" for windows
line_feed = "\n"

-- Program starts here
-- Loop for files given into the replace_file table
-- Then loop for lines into each file
-- Finally replace each line when its necessary
for _,filename in pairs(replace_file) do
    local fp,err = io.open(filename)
    if fp then
        local filechanged = 0
        local output = ""
        for inline in fp:lines() do
            local outline = inline
            for i,j in pairs(replace_string) do
                outline = string.gsub(outline,i,j)
            end
            if inline ~= outline then
                filechanged = filechanged + 1
            end
            output = output .. outline .. line_feed
        end
        fp:close()
        if filechanged > 0 then
            local fp, err = io.open(filename,"wb")
            if fp then
                fp:write(output)
                fp:close()
                print("CHANGED : "..filename.." ("..filechanged.." lines)")
            else
                print("FAILED : "..err.." (during file writing)")
            end
        else
            print("UNCHANGED : "..filename)
        end
    else
        print("FAILED : "..err.." (during file reading)")
    end
end