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I'm having trouble getting query-regex-replace to do what I want. I've read the docs several times and still can't figure it out. Here are a few examples of things I can't figure out how to do with query-regex-replace:

  1. Replace a bunch of whitespace on one line followed by "*" with just "*" (get rid of the whitespace.

EDIT - I got this to work with [[:space:]]+\* RET * RET

  1. Replace two forward slashes followed by non white space with two forward slashes and white space (insert a space before the first non white space character).

EDIT - I also got this to work with //\([^[:space:]]+\) RET // \1

  1. Get rid of blank lines (optionally of course because this is a query replace).

EDIT - I still cannot get this to work. Among other things, I tried these:

)[[:space:]]+{ RET ) { RET

and

)\s-+{ RET ) { RET

Thanks for any help.

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  • 2
    Please show an example line and the regex you tried. Commented Oct 2, 2016 at 3:37
  • I'm new to this forum format. Should I edit the original post or put the examples here? Also, I'm sure I tried at least five things for #1 above. Should I just put the most straightforward attempt? Commented Oct 2, 2016 at 17:10
  • Yes, edit the original post. Please show the regex expressions you tried. Commented Oct 2, 2016 at 17:43
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    Depending on what you're trying to do, there are a few options that may be more efficient than query-replace-regexp. Check out whitespace-cleanup for (1), comment-dwim for (2), and delete-blank-lines for (3). Unless you're batch cleaning up files, the options I suggested should be a better fit. Commented Oct 3, 2016 at 5:51
  • Love that C-x C-o to delete blank lines. Thanks for the link @Tianxiang Xiong Commented Oct 4, 2016 at 8:07

1 Answer 1

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To replace space and/or tab sequence followed by an asterisk to just an asterisk:

[ LiteralTabHere]+\*
*

That LiteralTabHere should be a literal tab char. Enter it by pressing C-q C-i.

You need the backslash before asterisk. Because the asterisk is a meta char, it means 0 or more items.

To insert a space before the first non-white-space character after 2 slashes:

//\([[:graph:]]+\)
// \1

To remove blank lines

\n\n\n+
\n\n

Each \n must be a literal return. To insert literal return, press C-q C-j.

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  • Shouldn't it be C-q C-j? For me, C-q RET gives a carriage return (like \r), not a newline (\n). Commented Oct 3, 2016 at 21:57
  • @npostavs you are right! Correcting it. Thanks. Commented Oct 3, 2016 at 22:46
  • To remove blank lines one may also use M-x flush-lines and when it prompts Flush lines containing match for regexp Enter $ and hit Return key Commented Oct 4, 2016 at 8:04
  • @Prasanna you mean with ^$. That flush all blank lines, sometimes one wants multiple blank lines collapsed to just one. Commented Oct 4, 2016 at 23:48
  • This is all great stuff. Thanks much. I am still having problems with replacement involving newlines. For instance, to replace ")" followed by blank space (including newlines) followed by "{" with ") {", I tried: ")[ \t\n]+{" ") {" It didn't work. Commented Oct 5, 2016 at 1:42

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