I've always seen reference to pwd as being very essential 'back in the day'. These days we have customized command prompts like PS1 that display the current directory and pwd is pretty outmoded. But when did the idea for ps1 get introduced into *nix systems? Watching this from the AT&T archives I can see that PS1 definitely did not exist in the seventies.
This variable is part of the shell,
$PS1 is used in
bash, the Bourne shell (
sh) and the
ksh, it is not used in the
The first UNIX shell was the Thompson Shell (which was also called
sh like the later bourne shell, the Thompson Shell was often called
osh on systems with both the Thompson and Bourne shell installed.) The Thompson shell used the variable
$P for the prompt.
Then the Bourne Shell was introduced which used
$PS1 to set the prompt.
ksh was based on the Bourne Shell, and also uses
set prompt = <something>.
So I think the first shell to use
$PS1 was the Bourne Shell.
Thompson Shell man page: https://etsh.io/man/osh.1.pdf
Bourne Shell man page: http://heirloom.sourceforge.net/sh/sh.1.html