Lua exact match line from file

So here is my scenario :

I have nginx-lua config, that it contains json data (from POST request) :

{
    "profile_name": "test",
    "number_from_json": "12",
}

In my /opt/file1.csv

1283813122344
12
12838138931316
128381383131

I have

So I'm having this config

location /reader_x {
   proxy_set_header X-Forwarded-Host $host;
   proxy_set_header X-Forwarded-Server $host;
   proxy_set_header X-Real-IP $remote_addr;
   proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
   proxy_set_header X-Url-Scheme $scheme;
   proxy_set_header X-Forwarded-Proto $scheme;
   proxy_set_header Host $http_host;
   proxy_redirect off;
   proxy_pass_request_body on;
   proxy_pass_request_headers on;
   proxy_ssl_verify off;
   if ($request_method = POST ) {
   rewrite_by_lua '
   ngx.req.read_body()
   local check_body = ngx.req.get_body_data()
   local data = ngx.req.get_body_data()
   json = require "dkjson"
   local json_parse = json.decode(check_body)
   local number_cut = json_parse.number_from_json
   local filepath = "/opt/file1.csv"
   local open_file = io.open(filepath, "rb")
   local second_one = open_file:read("*a")
   io.close(open_file)
   local  match0 = string.match(number_cut, second_one)
   if match0 then
   ngx.say("this is exactly matched 12")
else
   ngx.say("not matching")
   end
   ';
proxy_pass https://localhost:8421 ;

So I need only to match 12 unique number, not if the other numbers are contains "12"

Let me know if you need more info

You may be using the string.match parameters switched.

If I got the point, your question could be "how to match the whole word in Lua". This is a working example based on your scenario:

local number_cut = 12
local second_one = [[
1283813122344
12
12838138931316
128381383131
]]

local match0 = string.match(second_one, "%f[%w_]" .. number_cut .. "%f[^%w_]")

if (match0) then
    print "this is exactly matched 12"
else
    print "not matching"
end

https://ideone.com/P18FxV

Ref.: how to check if a word appears as a whole word in a string in Lua