quote_arg_test.lua

local lua = "lua"
local i = 0

while arg[i] do
    lua = arg[i]
    i = i - 1
end

local is_windows = package.config:sub(1, 1) == "\\"

local function quote_arg(argument)
    if is_windows then
        if argument == "" or argument:find('[ \f\t\v"]') then
            argument = '"' .. argument:gsub('(\\*)"', '%1%1\\"'):gsub('\\+$', "%0%0") .. '"'
        end

        return (argument:gsub('["^<>!|&%%]', "^%0"))
    else
        if argument == "" or argument:find('[^a-zA-Z0-9_@%+=:,./-]') then
            argument = "'" .. argument:gsub("'", "'\\''") .. "'"
        end

        return argument
    end
end

local function quote_command(arguments)
    local quoted_arguments = {}

    for i, argument in ipairs(arguments) do
        quoted_arguments[i] = quote_arg(argument)
    end

    return table.concat(quoted_arguments, " ")
end

math.randomseed(tonumber(arg[1]))

local chars = ""

for i = 1, 255 do
    local char = string.char(i)

    if char ~= "\26" and char ~= "\r" and char ~= "\n" then
        chars = chars .. char
    end
end

local function random_arg()
    local res = ""

    for _ = 1, math.random(15) + math.random(15) do
        local index = math.random(#chars)
        res = res .. chars:sub(index, index)
    end

    return res
end

local function dump(s)
    for i = 1, #s do
        print(i, s:byte(i, i))
    end
end

local function test(nargs)
    local args = {lua, "script.lua"}

    for _ = 1, nargs do
        local new_arg = random_arg()
        print(new_arg)
        table.insert(args, new_arg)
    end

    local cmd = quote_command(args)
    print("Command: " .. cmd)

    local handler = assert(io.popen(cmd, "rb"))
    local output = handler:read("*a")
    handler:close()
    print("Output: " .. output)

    local printed_args = {}

    for printed_arg in output:gmatch("[^\0]+") do
        table.insert(printed_args, printed_arg)
    end

    for i = 1, nargs do
        if printed_args[i] ~= args[i + 2] then
            print("Got: " .. tostring(printed_args[i]))

            if printed_args[i] then
                dump(printed_args[i])
            end

            print("Expected: " .. args[i + 2])
            dump(args[i + 2])
            os.exit()
        end
    end
end

while true do
    test(10)
end

script.lua

for _, argument in ipairs(arg) do
    io.stdout:write(argument, "\0")
end