How to download RSS files with and display their content with Lua

GistsScrapper.lua

-- This is a port of GistsScrapper.go <https://gist.github.com/M1que4s/b92073803b658c207fbdfaebc10a1512>

local curl = require('cURL') -- <https://github.com/Lua-cURL/Lua-cURLv3>
local feedparser = require('feedparser') -- <https://github.com/slact/lua-feedparser>

file_exist = function (file)
	local file_found = io.open(file, "r")
	if (file_found == nil) then
		return false
	end
	return true
end

function GetGists(user)
	local url = ('https://gist.github.com/%s.atom'):format(user)
	local filename = ('/tmp/%s.atom'):format(user)

	if not file_exist(filename) then
		-- HTTP Get
		local get_gists = curl.easy ({
			url = url,
			httpheader = {},
		})

		get_gists:perform({writefunction = assert(io.open(filename, "w+b"))})
		get_gists:close()
	end

	local gists = io.open(filename)
	local res = gists:read('*a')
	gists:close()

	if res == 'Not Found' then
		print('No gists found, this can happen due to connection problems.')
		return false
	end

	-- @TODO: There is a way to do this without downloading with cURL, but I don't have the library at the moment.
	local res = assert(feedparser.parse(res))

	if #res.entries ~= 0 then
		for i, post in pairs(res.entries) do
			print(('0%d. \27[1mDescription:\27[0m %s'):format(
				i, post.title
			))
		end
	else
		print(('User \'%s\' has no gists.'):format(user))
	end
end

GetGists(arg[1])