I need a regex to match tags that looks like <A>, <BB>, <CCC>, but not <ABC>, <aaa>, <>. so the tag must consist of the same uppercase letter, repeated. I've tried <[A-Z]+>, but that doesn't work. of course I can write something like <(A+|B+|C+|...)> and so on, but I wonder if there's a more elegant solution.
Add a comment |
1 Answer
You can use something like this (see this on rubular.com):
<([A-Z])\1*> This uses capturing group and backreference. Basically:
- You use
(pattern)to "capture" a match - You can then use
\nin your pattern, wherenis the group number, to "refer back" to what that group matched
So in this case:
- Group 1 captures
([A-Z]), an uppercase letter immediately following< - Then we see if we can match
\1*, i.e. zero or more of that same letter
References
answered Jun 24, 2010 at 13:24
polygenelubricants
385k129 gold badges568 silver badges627 bronze badges
1 Comment
SilentGhost
@John: indeed, why not start with "what is regular expression".