How do I edit current shell command in VI
You want set -o vi (add it to your ~/.bashrc). Then, to edit the current line, just hit Esc to enter command mode.

See http://www.gnu.org/software/bash/manual/bashref.html#Readline-vi-Mode

To edit the current command in a full-screen editor, set your VISUAL environment variable to vim (I assume you want vim), then in command mode in the current comment, hit v.



To show the mode in the prompt:

$ cat ~/.inputrc
set editing-mode vi
set show-mode-in-prompt on
set vi-ins-mode-string +
set vi-cmd-mode-string :