If a line starts with "A. " (no quotes) then I want the next line to start with "B. ".

For example:

I want to change this

A. blah blah blah
yada yada yada

to

A. blah blah blah
B. yada yada yada

Using the substitute command:

1. Use a capture group to get the lines starting with "A. " and ending with a new line.
2. Replace with capture group + "B. "

In case you need it, here's a hint on how to include the end of line: http://vim.wikia.com/wiki/Search_across_multiple_lines

Give it a shot. If you have problems post the command(s) you tried.

Maybe I was not clear, because that does not answer my question at all.

This is not a simple substitution.

This is not:

:%s/foo/bar/g

Finding the string to replace is easy. But how do I replace the string without replacing everything?

I do not want to change what is presently on the line starting "A. " I just want add a "B. " on the next line.

Apparently, you didn't look at that link and/or don't understand regex capture groups because both of these work for me:

This is my attempt, which works for the two-line example:

@dugan - After looking at your solution I see that it is not necessary to escape the periods, thus mine can be shortened a little:My motto: when in doubt escape, readability be damned!

This worked:

And this worked

I am going to have to do some research to find out way. But I'm fine with that.

Thanks for the answers.

You don't have to do as much escaping if you start the pattern with \v. It turns on something called "very magic mode".

I recommend using it whenever you use vim's version of regex.

Thank you.

I was wonder what that \v was.

FWIW:

After playing around with this, I have found that it's better to use the backslash before the dots. I also use a carrot before the A.

I use this now:

Of course there are a lot of ways to do this. Some methods may not require a backslash before the dot.

The way I used to do this, has caused some trouble.

or

In either of those methods, if the line started with An or an As, it might not work.

With the second method, if the line had an A[any char] anywhere in the line, it would put a B at the beginning of the next line.

caret

:^)