Cannot match string with optional whitespace using regex

Question

I'm trying to match the following strings:
/*virtual*/, /* virtual*/, /*virtual */ and /* virtual */

The regexp /\*\svirtual\s\*/ correctly matches the version with two spaces, however replacing \s by [\s]* does not match any of these strings... From reading the emacs RegularExpression reference document on the wiki I have assumed that this should create a regex matching my specification. I am still a bit new to regular expressions, any help (and explanation why the above is faulty) is welcome!

abo-abo · Accepted Answer · 2013-08-08 20:32:58Z

1

Try re-builder. It's so useful. And the expression is

"/\\* ?virtual ?\\*/"

Or, if you like to go with s-,

"/\\*\\s-?virtual\\s-?\\*/"

But note that it's not exactly a space, but whatever the syntax defines to be whitespace. So I could write a mode that designates all words like as whitespace, and your regex would match them.

edited Aug 8, 2013 at 20:32

answered Aug 8, 2013 at 15:03

abo-abo

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5 Comments

elemakil Over a year ago

Yes indeed, very useful! However, it turns out, it wasn't really my regex that was faulty but rather that I use then inside the function (s-contains? "REGEX" (buffer-substring beg-of-line end-of-line)) where the variables are the beginning/end of the current line. This does not support regular expressions. I will accept your answer because of the suggestion of re-builder and because of pointing out the problem with the whitespace class.

abo-abo Over a year ago

Btw, I usually prefer buffer-substring-no-properties. Not sure if it's faster, but it probably is. And more readable when debugging.

Syon Over a year ago

Just a note, if you prefer the expression to match only a single space instead of any whitespace (tab), use [C-q SPC] instead of [\s-].

phils Over a year ago

abo-abo: [\s-] matches any of backslash, lower-case s, or hyphen. I don't think you wanted any square brackets there.

abo-abo Over a year ago

@phis, actually it was because of re-builder. It actually thinks that [\s-] matches a space.

Jim W · Accepted Answer · 2013-08-08 15:03:58Z

0

Could be an emacs bug?

\*[\s]*virtual[\s]*\*

works in JS, see http://gskinner.com/RegExr/ (check 'global')

answered Aug 8, 2013 at 15:03

Jim W

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1 Comment

abo-abo Over a year ago

Emacs has a different regex syntax

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