Exactly that, all banks here in Brazil are exporting transactions with this kind of format (Its called CNAB file over here and they are probably using COBOL systems). You have different kinds of CNAB files, CNAB 200 where you have lines with 200 characters, CNAB 400...

Inside those files you have multiple chunks and every line contains information about a transaction. So if you wanna get the transaction amount you would look for all characters between character n10 and n20 for example. (Those positions are fixed and follow the bank template).

We had success parsing it with python/node, but i think spinning up a sqllite instance, reading straight from the file and doing some calculations would be much faster.