Sorry, this was back in the mid to late ‘90s.

Unfortunately, this was slightly 🤏 before my time. I was born back then but still a child which got his PC too late when I was 14 😢

ch0k1

Then, they have modified the MacOS very far away from BSD.
I recall SystemIV and SystemV as well as Solaris, BSD, AIX and the very beginnings of Linux.
They were not all interoperatalbe, each with slightly different commands.
You had to be careful of which system you were operating with the commands you used.

security

Meet Interlock — The new ransomware targeting FreeBSD servers

Then, they have modified the MacOS very far away from BSD. 
I recall SystemIV and SystemV as well as Solaris, BSD, AIX and the very beginnings of Linux.
They were not all interoperatalbe, each with slightly different commands.
You had to be careful of which system you were operating with the commands you used.