I am capturing Bar via a named groupA and I would like to re-reference groupA capture to get a second group.

Sample string :

Foo:Bar Lorem ipsum Bar-564875XC4 dolor sit amet

Regex to capture Bar in groupA :

Foo:(?<groupA>[^\s] )

Question : how to I complete this regex to re-capture <groupA> and get 564875XC4 in <groupB> ?

CodePudding user response：

I would write your regex in C# as:

Foo:(?<groupA>\w )(?: \w )* \k<groupA>-(?<groupB>\w )

More generally, you could also just use a numbered backreference:

Foo:(?<groupA>\w )(?: \w )* \1-(?<groupB>\w )

Demo

Explanation:

• Foo: match "Foo-"
• (?<groupA>\w ) match and capture first word in <groupA>
• (?: \w )* then match space followed by a word, zero or more tkmes
• match a single space
• \k<groupA> match the first captured word (again)
• - match "-"
• (?<groupB>\w ) match and capture term of interest in <groupB>

CodePudding user response：

Answer with back-reference by name:

Foo:(?<groupA>\w )(?: \w )* \g<groupA>-(?<groupB>\w )

Demo with named back-reference