yaml-query

#!/usr/bin/env lua5.1

local yaml = require "yaml";

local query = arg[1];

table.remove(arg, 1);

local query, string_out = query:gsub("^=", "");

local query_func = assert(loadstring("return "..query));

if #arg == 0 then arg[1] = "-"; end

for i, fn in ipairs(arg) do

	local f = io.stdin;

	if fn ~= "-" then

		f = assert(io.open(fn, "r"));

	end

	local yaml_doc = yaml.load(f:read("*a"));

	setfenv(query_func, yaml_doc);

	local result = query_func();

	if string_out == 1 then

		print(result);

	else

		print(yaml.dump(result));

	end

	f:close();

end