The shell is inevitable for using UNIX-like OS. Bash (Bourne-Again Shell) is used as standard in Linux etc., but I think that this is an enhanced version of sh (Bourne Shell), which is the ancestor of various shells.
KornShell is also one of the shells that can be used on such UNIX-like OS, but it seems that it is not often adopted as standard in recent years. This time, it is an article that let's try using such KornShell.
Let me briefly touch on my personal motives. O'Reilly's KornShell commentary book is sold at a bargain price at a used bookstore, and I picked it up directly. O'Reilly has a bash and tcsh / csh commentary book, but I didn't know that a KornShell commentary book was also published, so I bought it and read it.
It's a very rough recognition, but in terms of yesterday's abundance, I think the following recognition is fine.
sh < ksh < bash
It's not as sophisticated as bash, but it feels like it has enough features to be used interactively. Also, unlike csh / tcsh, it doesn't feel like it's significantly different from the bash system (?), So it's easy to get to that point.
To complicate matters, there are multiple implementations, such as because ksh was originally a proprietary license.
ksh This is the original version. Developed by David Korn. Initially proprietary, it became open source in the 2000s.
pdksh A public domain KornShell implementation.
mksh MirOS BSD is an implementation developed for BSD-based operating systems. It can be installed using apt on Debian, Ubuntu, etc.
I think it's rarely the default shell for current Linux distributions, but it's often included in official repositories, so you can install it in your package management and give it a try. I will. Aside from regular use, I think it's interesting from a historical point of view.