Select dois from response

lua/sourcer/init.lua

@@ -11,12 +11,33 @@ function M.lookup()
 
 	-- Execute the curl command and capture its output
 	local handle = io.popen(command)
-	local response = handle:read("*a")
+	local response = ""
+	if handle ~= nil then
+		response = handle:read("*a")
 		handle:close()
+	else
+		response = ""
+	end
+
+	-- select doi links from response
+	local b = 1
+	local doi_links = {}
+	while true do
+		local x, y = response:find("//doi/[a-zA-Z]+/10.[0-9]+/[0-9.]+/gm", b, false)
+
+		-- stop if no further occurrences are found
+		if x == nil or y == nil then
+			break
+		end
+
+		-- save substring to doi_links
+		doi_links:insert(response:sub(x, y))
+		b = y
+	end
 
 	print("Keywords: " .. keywords)
 	print("URL: " .. url)
-	print("Response: " .. response)
+	print("links: " .. doi_links)
 end
 
 return M