converting a search to a replace in vim

I just googled something I’ve always wanted to know how to do in vim, and was surprised how quickly I found the answer.

In vim, there are separate modes for searching and commands. This generally works well as they have separate completion buffers and since I do them a lot, it keeps my command history from cluttering up my search history and vice versa. The area where I’ve wished that they were unified is when I want to convert from a search to a substitution expression. Normally in vim you do search expressions in search mode and command expressions in command mode. For example, if I wanted to search for trailing whitespace I might type:

/\s\s*

If I want to replace it with an empty string through the whole file I might type:

:%s/\s\s*//g

I can’t remove the / at the front of the command line with a backspace and replace it with a colon, so until I learned the tip I’m about to reveal I had to retype it. No longer.

The StackOverflow answer I found for the query, Convert vim / search to search and replace without retyping regular expression, suggests this remarkably simple technique:

You can type

/search_term

and then

:%s/<ctrl-r>// etc

where you actually press ctrl+r and then / to insert the search term.

It works! No longer do I desire for search and command modes to be unified.