Mark,
thanks for your answer.
Your Phyton RT-11 code looks good to me, I'll rely on it at least as
reference.
Joerg
I've written (bad?) Python code to manipulate RT-11 filesystems, including on
TU58 tape images:
https://github.com/NF6X/pyRT11
I don't remember which specific documentation I referred to when I wrote this
code, but it may well have been something like this manual:
http://bitsavers.trailing-edge.com/pdf/dec/pdp11/rt11/v5.6_Aug91/AA-PD6PA-TC_RT-11_Volume_and_File_Formats_Manual_Aug91.pdf
