I want to replace if (condition) //comment \n\s*{ (\n - newline, \s* 0 or more whitespaces), or rather restructure it, so brace is on same line as if and comment is moved to next one and is indented by one tab more.

It's a Vim practice task, so please don't give me whole solution, instead help me understand what I'm missing.

My regex works and catches what I want (starting with comment on purpose):

:%s#\(//\)\(.\)*\n\(\s\)*{#{\r\t\3\1 \2#g

My replace pattern however doesn't catch groups, using \1 \2 \3 doesn't work. To be more precise, only \1 works.

I get a brace, a new line, one more indent as wanted, then groups (except for \1 (meaning //) are NOT there:

if (condition) {

No comment text, no tabs/whitespaces aside from one I specifically put there. What am I missing?

  • 1
    What does that \n and \s mean? Are they literal characters or used as their original meaning?
    – SibiCoder
    Aug 22, 2016 at 11:40
  • 3
    I think \n and \s are newlines and space characters, as his given regex won't match otherwise.. from what I could make out, (.\)*\n should be (.*\)\n
    – Sundeep
    Aug 22, 2016 at 11:44
  • 1
    @spasic please post this as an answer so I can accept, as this is precisely what I was missing, my thanks. Groups were captured as they were stated, duh! Aug 22, 2016 at 12:21
  • 3
    Another note: it's not really worth putting constant text like "//" into a group, because you could just put // on the other side, rather than \1
    – DJMcMayhem
    Aug 22, 2016 at 13:57
  • @DJMcMayhem definitely. It's just that I was trying to see if there's a problem with groups or what I put in them, thus // was used as test input. Thank you though! Aug 22, 2016 at 15:02

1 Answer 1


Given this text

if (condition) //comment

the following substitute

:%s#\(//\)\(.\)*\n\(\s\)*{#{\r\t\3\1 \2#g


if (condition) {
     // t

I don't fully understand, but \(.\)* would repeat the atom of capturing any single character zero or more times, resulting in capturing the last character of first line t

As the intention was to capture all the text following //, * should have been inside the capturing group. Same goes for \(\s\)*. The g flag is not needed as well

:%s#\(//\)\(.*\)\n\(\s*\){#{\r\t\3\1 \2#

which gives

if (condition) {
        // comment

Using the very magic modifier, the regex would be (see :h \v for help)

:%s#\v(//)(.*)\n(\s*)\{#{\r\t\3\1 \2#
  • 3
    Thank you. Very magic comes next, it's just that when debugging I went back to escaping manually as I knew it more. Good thing about /g, I used it so often lately that I started appending it by habit... Aug 22, 2016 at 15:01

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