I'm using bash on Debian 11. But how may I open a Bourne, Korn or C-Shell if I am willing to? I am reading a book speaking about _Bourne Shell_ (the ancestor of `bash` = _Bourne-Again Shell_ I'm currently using), _Korn Shell_ and _C-Shell_. I was curious, and willing to experience them. On a `bash` terminal under _Debian 11_ I've attempted to execute: bsh ksh csh but without success. How shall I do that?

`csh` and `ksh` are available in the eponymous packages:


sudo apt install csh ksh


Depending on the vintage of the book you’re reading, and the shells it’s based on, you might find differences in behaviour with the versions of `csh` and `ksh` currently available in Debian.

The Bourne shell isn’t available directly, but `dash` (which is installed by default on Debian) is a descendant of the Almquist shell, which was written as a clone of the Bourne shell. `dash` has been made POSIX-compliant however, which means it’s no longer compatible with the Bourne shell.

Outside of Debian, you can find an updated version of the Bourne shell in the Heirloom Project.