Frd files are not really suitable for reading directly but the syntax is explained here: https://www.dhondt.de/cgx_2.22.pdf#section.11
It’s much easier to read .dat files generated for history output requests.
There is the COORD output variable but it’s only for integration point coordinates.
Here’s a script to work with .frd files: getResultsFromFRD.py : Extract Results from PrePoMax/CalculiX