[Exim] ${readfile EOL question

Hello all,

regarding to my question a few days ago, I now have a new problem
with the ${readfile expansion item.
As described in the spec of 4.40, the syntax is

${readfile{<file name>}{<eol string>}}

so that I can define an eol string.
But how do I figure out, what my system (or file?) uses for the
eol string?

Thanks,

Michael