Install cl-flexi-streams by entering the following commands in the terminal:
sudo apt update sudo apt install cl-flexi-streams
Flexi-streams: Flexible bivalent streams for Common Lisp
FLEXI-STREAMS implements "virtual" bivalent streams that can be layered atop real binary or bivalent streams and that can be used to read and write character data in various single- or multi-octet encodings which can be changed on the fly. It also supplies in-memory binary streams which are similar to string streams. . FLEXI-STREAMS is currently not optimized towards performance - it is rather intended to be easy to use and (if possible) to behave correctly.