Posix Get Opt

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Pure Lua

The following should behave exactly according to the [POSIX/SUS definition], except that the return value differs slightly so that there's no global state.

Usage

--
-- opt is either the option character, "?", or ":".
--
-- If opt is the option character, arg is either a string or false--if optstring
-- did not specify a required argument.
--
-- If opt is either "?" or ":", then arg is the unknown option or the option
-- lacking the required argument. Like the standard says, there's really only
-- one scenario for ":" to ever be returned. And per the standard, unless
-- optstring begins with a colon, "?" is returned instead.
--
for opt, arg in getopt(":a:b", ...) do
        print("opt:", opt, "arg:", arg)
end

Code

--
-- getopt(":a:b", ...) -- works just like getopt(3).
--
-- Send bug reports to william@25thandClement.com.
--
function getopt(optstring, ...)
	local opts = { }
	local args = { ... }

	for optc, optv in optstring:gmatch"(%a)(:?)" do
		opts[optc] = { hasarg = optv == ":" }
	end

	return coroutine.wrap(function()
		local yield = coroutine.yield
		local i = 1

		while i <= #args do
			local arg = args[i]

			i = i + 1

			if arg == "--" then
				break
			elseif arg:sub(1, 1) == "-" then
				for j = 2, #arg do
					local opt = arg:sub(j, j)

					if opts[opt] then
						if opts[opt].hasarg then
							if j == #arg then
								if args[i] then
									yield(opt, args[i])
									i = i + 1
								elseif optstring:sub(1, 1) == ":" then
									yield(':', opt)
								else
									yield('?', opt)
								end
							else
								yield(opt, arg:sub(j + 1))
							end

							break
						else
							yield(opt, false)
						end
					else
						yield('?', opt)
					end
				end
			else
				yield(false, arg)
			end
		end

		for i = i, #args do
			yield(false, args[i])
		end
	end)
end

See Also

• GetOpt