Earlier this year I discussed trying the KornShell as my daily driver, but I didn’t know the difference between the major versions. Perhaps this brief summary post might be useful to someone.

  • ksh93 is the evolution of the canonical ksh88 by David Korn and Morris Bolsky at AT&T. It was originally proprietary, but has since been released into the public domain. It’s actively maintained, and shipped with macOS. It’s officially spelled KornShell.

  • pdksh is the Public Domain Korn Shell, released in response to ksh88 being proprietary. NetBSD’s default install includes this variant, and it was the first Korn Shell I used. This, and all its other derivatives, are spelled Korn Shell with a space.

  • mksh is the MirBSD/MirOS Korn Shell. Based on pdksh. The landing page is outdated, but it’s still actively maintained.

  • tcksh is the TENEX Sea Kucumber Shell. Blatantly made up by me.

  • oksh is the Portable OpenBSD Korn Shell. Based on pdksh, with enhancements. I use this variant now, for a few delightful reasons I will soon blog about.