Can I navigate backwards by word (not WORD) in command-line mode?

Question

If I'm in command-line mode in vim, and I have the current command line entered (cursor position shown with |):

:somecommand somefilename.txt|

I'd like to navigate backwards so that the cursor is behind the .:

:somecommand somefilename|.txt

Is there a way I can do this with a single command? In normal mode, I could use bb to move back two words, but it seems that the only keybinding I can find in command line mode that's relevant to words is Shift-Left, and this moves by WORDS, not words (i.e. it ignores all punctuation and only looks at whitespace), so the cursor ends up here:

:somecommand |somefilename.txt

If it's relevant, I would like to use this as part of a mapping, so it doesn't matter if it's a bit fiddly to type.

Answer 1

Since you don't mind a mapping, we can use

cnoremap <S-Left> <C-f>bb<C-c>

This remaps <S-Left> to the behavior you described, using <C-f> to switch to edit the command line in normal mode. <C-c> then switches back to command line mode.

For details, refer to :h cmdline-window

Answer 2

I don't think there is a built-in way to do it with bare cmdline accroding to :h cmdline.txt.

But if you are into heavy edit of the command line I suggest to use :<C-f> or q: to open command-line window where you can edit it with 'normal' vim commands.

See :h cmdline-window for details.