Use regex to substitute a match except the first and last characters

Question

Maybe the title isn't to explicative; feel free to improve it.

I have the text below:

1. Intro          |timetracking-intro|$
2. Uso            |timetracking-usage|$
3. Comandi        |timetracking-commands|$

I want to replace all space between the title and the tag with dots, but the first and the last, like this:

1. Intro ........ |timetracking-intro|$
2. Uso .......... |timetracking-usage|$
3. Comandi ...... |timetracking-commands|$

After an hour of attempts without success I can't understand this:

1. :s/\A\s\A/./gc
   This match also the firts space after the word "intro". Why? I used \A to not match the first space! (in the picture I grouped, \(\A\s\A\) but is the same).
   

2. :s/\(\A\zs\s\ze\A\)/./gc
   but this regex match only alternate spaces, and match also the last space!!
   

I had also some more funny results... :-/

Can anyone explain me why and how to do what I want?

Answer 1

I would propose you:

:s/\s\@<=\s\s\@=/./g

Where:

• \s\@<= match only if the previous character is a space
• \s\@= match only if the next character is a space

Since both match with zero width you don't have the one out of two effect.

Answer 2

Try this:

:%s/  \+/\=' '.repeat('.',len(submatch(0))-2).' '/g

%s/PATTERN/\=EXPR/g substitutes all occurrences of PATTERN with the result from evaluating EXPR

\+ matches at least 2 spaces

len(submatch(0)) is the length of the currently matched text

repeat('.',len(submatch(0))-2) creates the sequence of dots

' '. .' ' surrounds it with spaces

Answer 3

There may be a better way, but this is what I came up with:

:s/\S\s\zs\s*\ze\s\S/\=substitute(submatch(0), '\s', '.', 'g')/

\A matches anything that isn't an alphabetic character, so it makes sense that it matches a space. Instead, you'd want to use \S to find the boundaries of the spaces.

The pattern part can be explained as: "Find a non-space followed by a space. Then find 0 or more spaces, which will be the part we operate on in the replacement part. Then find another space followed by a non-space".

The replacement part then uses \=substitute() to then do a find/replace on the spaces found between the \zs and \ze. I'm not sure if there's another way to dynamically do a replacement when there's a variable number of characters in the captured match.