The macro means: \C-a: beginning of line $: self-insert (: self-insert \C-e: end of line ): self-insert So if your prompt (with | for cursor) looks

The macro means: \C-a: beginning of line $: self-insert (: self-insert \C-e: end of line ): self-insert So if your prompt (with | for cursor) looks like this: grep 'blah blah' |some_file And you execute that macro, you get: $(grep 'blah blah' some_file)| Which is correctly quoted and I think always correctly quotes whatever is at the prompt (unless you e.g. get half way through a string and press enter so the beginning of the prompt is halfway through a string, or maybe if you have multiple lines)