You are working on a documentation file userNotes.txt with some members of your software development team. Just before the file needs to be submitted, you manager tells you that a company standard requires that two blank spaces be left between the end-of-sentence period (.) and the start of the next sentence. (This rule does not affect sentences at the very end of a line.)
For example, this is OK: Turn the knob. Push the “on” button.
This is not: Turn the knob. Push the “on” button.
Asking around among your team members, you discover that some of them have already typed their sentences in the approved manner, but others have inserted only a single blank between sentences.
You need to fix this fast, and the first thing you want to do is to find out how bad the problem is.
What command would you give to list all lines of userNotes.txt that contain sentence endings with only one blank before the start of the next sentence?