Regular expression in Vim to match group capture

Question

I want to find the words which contain the same string repeated twice. (e.g. wookokss(ok/ok), ccsssscc(ss/ss)). I think the expression is \(\w*\)\0.

Another try is to find the words which consist of the same string repeated twice. My answer is \<\(\w*\)\0\>. (word beginning + grouping(word) + group capture + word ending)

But they don't work. Could anybody help me?

Answer 1

To find a string repeated twice in a word, which is longer than two characters, you can use

/\(\w\{2,}\)\1

To match a whole word which contains beforementioned string, you can use

/\<\w\{-}\(\w\{2,}\)\1\w\{-}\>

Little bit of explanation

• \1 - matches the same string that was matched by the first sub-expression in \( and \) (\0 matches the whole matched pattern)
• \{n,} - matches at least n of the preceding atom, as many as possible
• \{-} - matches 0 or more of the preceding atom, as few as possible
• \w - the word character ([0-9A-Za-z_])
• \< - the beginning of a word
• \> - the end of a word

More in :help pattern

Answer 2

1.) words which contain the same string repeated twice. (e.g. wookokss(ok/ok),

To find words containing two or more repeated word characters try

\(\w\{2,}\)\1

\1 matches what's captured in first group.

2.) find the words which consist of the same string repeated twice...

To capture \w\+ one or more word characters followed by \1 what's captured in first group

\<\(\w\+\)\1\>

should be about it. Have a look at this tutorial.