Cat

tArgs = { ... }

if #tArgs == 1 then
    if fs.exists(tArgs[1]) then
        file = fs.open(tArgs[1], "r")
        for line in io.lines(tArgs[1]) do
            script = file.readLine()
            if script ~= nil then
                print(line)
            else
                break
            end
        end
        file.close()
    else
        error("Can't find file " .. tArgs[1])
    end
elseif #tArgs >= 1 then
    error("More than one file is NYI")
elseif #tArgs <= 1 then
    print("Usage: ")
    print(shell.getRunningProgram() .. " <file>")
end