want shell should I learn 15

Because you told me that was what you could use in bash!

You do if you use bash.

I wasn't being deliberately btuse. I genuinely thought that that means that you can bind vi to a key sequence that edits your command line.

So - where is the vi editor? I did understand from your comments that one could put a group of lines from the history and edit them in the editor, then execute the result. And the bash man page, while particularly incomprehensible on the subject, looks as though it says that's what one can do:

fc -s pat=rep cmd Fix Command. In the first form, a range of com mands from first to last is selected from the his tory list. ...

If the first form is used, the return value is 0 unless an invalid option is encountered or first or last specify history lines out of range. If the -e option is supplied, the return value is the value of the last command executed or failure if an error occurs with the temporary file of commands.

I was asking how!

How do you invoke it?

Uh - then you are simply not talking about anything, because your premise is false: readline is not an acceptable programming editor.

What's the command or binding to do that?

Well, 1GHz is enough.

Does it somehow take longer to execute machine instructions when their aim is to invoke a script? System call overheads are in the microsecond range.

As much as programming in bash does.

Of course it is - that's what "csh" means, and I used to run "C--", an interpreted version of C, as my shell for a while.

Which word do you not understand?

Peter