To not have hardcoded filenames in gnuplot script https://wiki.ubuntuusers.de/Gnuplot/#Stapelverarbeitung-Zugriff-auf-Umgebungsvariablen
We do this in python script
Source https://commons.wikimedia.org/w/index.php?title=File:Euro_exchange_rate_to_TRY_-_Turkish_Currency_and_Debt_Crisis_2018.svg&oldid=320846888