CP/M predated from previous engineering as well...

Most if not all modern Operative Systems have deliberately copied or have been "inspired" by DEC's 10-11ish interactive OSes.

TOPS10, RT-11, RS-TS all those operative systems made the history of the command line and I seem to remember reading that Mr. Kildall's first real commercial incarnation of CP/M (1.3) used to spot those similarities as a features not as a rip-off.

PIP (Peripheral Interchange Program) is the classical example.

Nevertheless CP/M and RT-11 are two wonderful exercises of effective minimalism: they did their job and they did it well (they do, actually, as far as I am concerned if I want to have some fun I switch on either my Altos 8000 or my 11-23).

GaB