Sample of N2O_ASYNC usage as Telegram Bot that counts number of users in particular channel or group and records it to files in CSV format. Extend it to your needs.

  {nynpo, [{bot,"548231922:AAHmXMMr38XGtH0tJMDUdiByheT2mZ7qkVI"},
           {timer,{0,0,5}},
           {rooms,["CanYaCommunity","HaskellRu","RuHaskell"]}]},

Bot is your API key, timer is granularity of tracking, rooms is a list of room you want to track.

$ brew install erlang
$ ./nynpo repl

$ cat HaskellRu
2018/2/27, 10:52:40, "HaskellRu", -1001043143583, 670
2018/2/27, 10:52:47, "HaskellRu", -1001043143583, 670
2018/2/27, 10:52:52, "HaskellRu", -1001043143583, 670
2018/2/27, 10:52:57, "HaskellRu", -1001043143583, 670

$ ./nynpo dep com pla
$ ./nynpo release script nynpo

Tha last command will recreate nynpo escript executable runnable by Erlang ERTS.

• Maxim Sokhatsky