Sorry if that didn't come across clear enough. When I said that a lot of the current shells can learn a thing or two from ksh, I was talking about the scripting

Sorry if that didn't come across clear enough. When I said that a lot of the current shells can learn a thing or two from ksh, I was talking about the scripting part. And there it's mostly POSIX/Bourne with a few things from ksh and some idiosyncratic new features. The rc shell from Plan 9 was an interesting approach, too. Zsh/bash/fish don't try to innovate in that area. The readline library (which is the basis for most of the interactive history features) is quite nice, but I'd much rather save me some repetition than make sure that the repetitive commands can be entered fast enough. I guess it all comes down to how repetitive your shell usage is. If you're very exploratory, i.e. use different paths, systems and command line options all the time, completion helps, just like it helps you navigate a huge mess of a class inheritance tree. If you find yourself able to factor out common tasks, scripting is a bit more helpful. And most of the time, I fall into the second camp, which is why I've never found fish all that attractive. Which is what I wanted to point out (although a bit too bluntly – curse my German nature!).