With debugging, NSE prints out the script-args string and the pretty printed

final script-args table. The rationale is, unfortunately shells interpret
quotes differently and so it can be hard to tell exactly what NSE ends up
seeing/producing. [Some discussion in #nmap on Freenode resulted in this
addition.]

nse_main.lua

@@ -1152,6 +1152,7 @@ end
 
 do -- Load script arguments (--script-args)
   local args = cnse.scriptargs or "";
+  print_debug(1, "Script Arguments seen from CLI: %s", args);
 
   -- Parse a string in 'str' at 'start'.
   local function parse_string (str, start)
@@ -1224,6 +1225,11 @@ do -- Load script arguments (--script-args)
     end
     nmap.registry.args = tmpargs
   end
+  if debugging() >= 2 then
+    local out = {}
+    rawget(stdnse, "pretty_printer")(nmap.registry.args, function (s) out[#out+1] = s end)
+    print_debug(2, concat(out))
+  end
 end
 
 -- Update Missing Script Database?

nselib/stdnse.lua

@@ -24,6 +24,7 @@ local require = require;
 local select = select
 local setmetatable = setmetatable;
 local tonumber = tonumber;
+local tostring = tostring;
 local type = type
 
 local ceil = math.ceil
@@ -1159,4 +1160,39 @@ function output_table ()
   return setmetatable({}, mt)
 end
 
+--- A pretty printer for Lua objects.
+--
+-- Takes an object (usually a table) and prints it using the
+-- printer function. The printer function takes a sole string
+-- argument and will be called repeatedly.
+--
+-- @args obj The object to pretty print.
+-- @args printer The printer function.
+function pretty_printer (obj, printer)
+  if printer == nil then printer = print end
+
+  local function aux (obj, spacing)
+    local t = type(obj)
+    if t == "table" then
+      printer "{\n"
+      for k, v in pairs(obj) do
+        local spacing = spacing.."\t"
+        printer(spacing)
+        printer "["
+        aux(k, spacing)
+        printer "] = "
+        aux(v, spacing)
+        printer ",\n"
+      end
+      printer(spacing.."}")
+    elseif t == "string" then
+      printer(format("%q", obj))
+    else
+      printer(tostring(obj))
+    end
+  end
+
+  return aux(obj, "")
+end
+
 return _ENV;