How to redefine a command in Vim?

Question

In vim, in my .vimrc, how can I redefine a command (i.e. :e) as something else? I want to redefine :e * as :tabe *.

Answer 1

As I understand it, you can't. User defined commands must have an uppercase first letter.

  :help :command

for more information

Answer 2

I figured out a way to do it. See How to disable a built-in command in vim . From that, we can see that we can use cabbrev to change what a command does. For my needs, cabbrev e tabe is perfect.

But we can generalize this solution to make commands starting with lower case characters accessible to users for user-defined ones: use cabbrev to (re)define a built-in command as a user-defined one. As such, we are able to redefine built-in commands as well as user-defined ones.

Here's an example, which is equivalent to my aforementioned solution to my problem:

:command -nargs=+ E :tabe "<args>"
:cabbrev e E

That's all.

Answer 3

cnoreabbrev workaround

The best workaround without a plugin that I have seen so far is:

cnoreabbrev <expr> e getcmdtype() == ":" && getcmdline() == 'e' ? 'tabe' : 'e'

---

If you use a simple:

cnoreabbrev e E

as suggested by @Yktula would break your command if you want to do:

echo e f

which would become:

echo E f

instead.

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As explained by @pydave in the comments, the cmdalias plugin adds a simpler interface to doing the safe alias simply as:

:Alias e tabe

At the time of writing the plugin also uses the getcmdtype() == ":" technique to implement its functionality.