Undo tab expansion?

Question

In bash, pressing Tab invokes the programmable completion feature and either (a) expands to a unique path or command matching what's typed or (b) a list of possible options.

Is it possible to undo the entire expansion made by pressing Tab?

Example:

1. My current command is ls application/views/.
2. There are two possible expansions on that command: helpers/ and scripts/.
3. I type heTab, which expands to helpers/.
4. I realize I meant the other one scripts.
5. Now I have to delete the entire expansion "helpers/".

I usually just backspace over the entire path (helpers/ in this case), because I find striking readline undo Control+_ tedious. What I'd like is a single key sequence that deletes the full match of the expansion, regardless of any characters I initially typed and any spaces or slashes added to the end.

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Running list of key sequences suggested by comments or my own read of the GNU reference. None of these accomplish the goal:

• Meta+b -- Moves back to the previous / or , but doesn't delete.
• Meta+Del -- Deletes one character, not the entire word.
• Meta+Backspace -- Moves back one character without deleting.
• Control+W -- Deletes the entire path, not just the expansion. So in my example, after pressing Tab, bash expands that to ls application/views/helpers, then when I press Control+W, bash deletes application/views/helpers.

If relevant, I'm using the vi editing mode on a Gentoo Linux box. I've checked my configuration and I've not remapped any characters.

Answer 1

You're giving the keystrokes, but not the readline bindings, this can explain differences in observed behaviour (try bind -p).

The only way I can think of to do exactly what you ask is to use a custom completion function that saves the buffer state, and a separate key binding which invokes a companion shell function to restore it.

In addition to @Mark Plotnick's excellent suggestion to use menu-complete, other readline/bash options are:

• shell-backward-kill-word this removes a "shell word" which in the case of an expanded file or path will be the complete file or path name
• backward-kill-word this removes a "readline word", which in the case of a file or path will be a file or directory name component, including the trailing /
• undo which undoes each change atomically, but this almost certainly requires several attempts to fully remove a complete expansion, this is almost certainly the function you have bound to to ctrl-_ (bash default)
• set-mark and kill-region are lesser used readline features, set-mark marks the current cursor position, and kill-region deletes from the mark to the cursor. This requires you to invoke set-mark (default meta-space) in advance so that you can later use kill-region to delete back to it (no default binding)
• possible-completions (bound to meta-=) which lists the completions without modifying the command buffer

You could also write your own function to modify the input buffer, and bind it to a function (here's one I made earlier) but I don't see how that would be very much better than backward-kill-word in this case.

You can test bindings on the fly without using .inputrc using bash's bind command, e.g.:

bind "\C-o: backward-kill-word"
bind "\C-o: shell-backward-kill-word"

backward-kill-word is the best fit, default binding is metactrl-h. set-mark/kill-region would be better, but I can't think of a neat way to automate the use of this though.