Lua Script in suricata to detect the change in file - lua

Question

I am new in lua programming. I was looking for a lua script that can read the file being downloaded through Suricata from the internet and detect if file is changed. Any help would be appreciated. Thanks in advance.
Something like this:
function init(args)
return {http.response_body = tostring(true)}
end
local function read_file(path)
local file = open(path, "rb") -- r read mode and b binary mode
if not file then return nil end
local content = file:read "*a" -- *a or *all reads the whole file
file:close()
return content
end
local fileContent = read_file(path-to-where-previous-file-is-stored);
local fileContent2 = read_file(init());
if fileContent != fileContent2:
print("File changed")
and block if contents are same
drop http any any -> any any (msg:"NVISO PDF file lua"; flow:established,to_client; luajit:pdfcheckname.lua; classtype:policy-violation; sid:1000000; rev:1;)

Answer 1

Unless you have some other open function that is now shown in your snippet local file = open(path, "rb") should be replaced with local file = io.open(path, "rb")
local fileContent2 = read_file(init()); will cause problems as init() will return a table, not a path string. This will cause an error when calling io.open
if fileContent != fileContent2:
print("File changed")
is syntactically incorrect.
Replace it with
if fileContent != fileContent2 then
print("File Changed")
end
Also a name like file2Content would make more sense as it is not the second content of file but the content of file 2. But that's just my personal opinion.