Yes, this is the way which would fit my purpose.
However, I want to have a certain amount of reports stored in this file, until this file gets for example 2 MB. Then, the size would not increase anymore, appending new reports and deleting old ones automatic.
So I have to get into this file, get it's size and delete the first lines, until the size fits again.
I think, there must be a way to control textfiles line by line, but I never worked with this kind of files.