如何使用命令或部分命令预填充终端提示符？

Question

I would like to write a command/function that will prepopulate my terminal prompt with a partial command or text. I need to prefix my git commit messages and I was thinking it would be useful for this (and other uses) if I could prefill the prompt with a partial command rather than always needing to retype the same thing.

> gencommit
> git commit -m "ABC-123: 

In the code snippet above, git commit -m "ABC-123: is placed on the command line and I would simply be able to add a commit message and execute the command.

echo is the only thing that comes to mind but that does not do what I want, If gencommit used echo it would look something like this.

> gencommit
git commit -m "ABC-123:
> 

Answer 1

As far as I know, bash doesn't provide any way to write to the Readline buffer programatically. ( zsh does, as an aside.) One alternative is to make gencommit a Readline macro. For example, add this to your .inputrc file (creating the file if necessary):

"gencommit": "git commit -m \"ABC-123:"

One thing about his approach that I find disconcerting is that because a macro is text that gets replaced immediately, Readline won't actually echo the text you are typing to the screen until it has determined what macro you are typing, so while you are typing gencommit , nothing appears on your screen until you finish, then the expansion text appears. Worse, if you make a mistake while typing, you have to cancel the command and start over.

Better is to define an alias

alias gencommit='git commit -m "ABC-123:'

and, after typing gencommit on the command line, use the shell-expand-line Readline function (bound to M-! by default; M is the meta key, which is either Alt or Esc, depending on your platform and terminal emulator settings) to expand it to the replacement text. (This tries to expand anything on the command line: aliases, parameters, history expansions, etc. There is a dedicated alias-expand-line function that only expands aliases, but it is unbound by default. I leave it as an exercise to bind this command to an unused key sequence if you like.)

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As I alluded to zsh , the command in that shell would simply be

print -z 'git commit -m "ABC-123:'