This script will help you find a "main_arena" offset value for both 32-bit and 64-bit libc.so.6 during the CTF (e.g., heap-overflow chals) or your personal linux exploitations.
Tested up to libc version 2.29.
$ python patlabor.py
_ _ _
_ __ __ _| |_| | __ _| |__ ___ _ __
| '_ \ / _` | __| |/ _` | '_ \ / _ \| '__|
| |_) | (_| | |_| | (_| | |_) | (_) | |
| .__/ \__,_|\__|_|\__,_|_.__/ \___/|_|
|_| [bigb0ss]
[*] Usage: python patlabor.py "libc.so.6" of your choice