Simplified getopt for lua

Lua doesn’t include getopt. I have written this very simple implementation. It is actually a simplified version of AlternativeGetOpt. It is usable but absolutely not user-proof! Good enough for your own scripts though.

function getopt(o)
  local p = {}
  for k,v in ipairs(arg) do
    if v:byte(1) == 45 then
      local l = v:sub(2,2)
      if o:match(l) then
        p[l] = arg[k+1]
      else
        p[l] = true
      end
    end
  end
  return p
end

You can test for example with the following main function:

function main()
   local opts = getopt("up")
   local user = opts.u and opts.u or "default"
   local pass = opts.p and opts.p or "secret"
   local root = opts.a and true or false
   print(user, pass, root)
end

Usage examples:

$ getopt
default	secret	false
$ getopt -u lyderic
lyderic	secret	false
$ getopt -u lyderic -p password
lyderic	password	false
$ getopt -a -u lyderic -p password
lyderic	password	true
$ getopt -a -u lyderic -w
lyderic	secret	true

The full code is on github: https://github.com/lyderic/scripts/blob/master/getopt.lua