Command interpretation

command.lua

input = [[ms slap "Mister Sandman" 23 im"nots"ure ""what"s going on"]]
input = " " .. input .. " "
f1 = "%s+%S"
f2 = "[^%s\"]%s+"
f3 = "\"%s+"

local cursor = 0
local quote = false
local word = false
local out = {}
while cursor < #input do
  local a, b
  if not quote and not word then
    a, b = input:find(f1, cursor)
    if a then
      cursor = a
      local t = input:sub(b, b)
      if t == "\"" then
        quote = b
      else
        word = b
      end
    end
  elseif quote then
    a, b = input:find(f3, cursor)
    if a then
      cursor = a
      table.insert(out, input:sub(quote + 1, a - 1))
      quote = false
    end
  else
    a, b = input:find(f2, cursor)
    if a then
      cursor = a
      table.insert(out, input:sub(word, a))
      word = false
    end
  end
  cursor = cursor + 1
end

for _, word in ipairs(out) do
  print(word)
end