Regex - capture multiple groups and combine them multiple times in one string

Question

I need to combine some text using regex, but I'm having a bit of trouble when trying to capture and substitute my string. For example - I need to capture digits from the start, and add them in a substitution to every section closed between ||

I have:

||10||a||ab||abc||

I want:

||10||a10||ab10||abc10||

So I need '10' in capture group 1 and 'a|ab|abc' in capture group 2

I've tried something like this, but it doesn't work for me (captures only one [a-z] group)

(?=.*\|\|(\d+)\|\|)(?=.*\b([a-z]+\b))

You can't do it properly without an infinite-width lookbehind or some extra code. Is it used in C#? — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Aug 22, 2019 at 8:59
Do you always have exactly 4 values in between pipes, per line? — Tim Biegeleisen
– Tim Biegeleisen, Commented Aug 22, 2019 at 8:59
I don't know/use Ruby, but I would suggest just extracting the first value, then splitting your string on ||, and finally piecing it back together. — Tim Biegeleisen
– Tim Biegeleisen, Commented Aug 22, 2019 at 9:16

Tom Lord · Accepted Answer · 2019-08-22 13:28:34Z

2

I would achieve this without a complex regular expression. For example, you could do this:

input = "||10||a||ab||abc||"
parts = input.scan(/\w+/)   # => ["10", "a", "ab", "abc"]
parts[1..-1].each { |part| part << parts[0] }   # => ["a10", "ab10", "abc10"]

"||#{parts.join('||')}||"

answered Aug 22, 2019 at 13:28

Tom Lord

28.4k5 gold badges54 silver badges86 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Cary Swoveland · Accepted Answer · 2019-10-20 22:49:50Z

1

str = "||10||a||ab||abc||"

first = nil
str.gsub(/(?<=\|\|)[^\|]+/) { |s| first.nil? ? (first = s) : s + first }
  #=> "||10||a10||ab10||abc10||"

The regular expression reads, "match one or more characters in a pipe immediately following two pipes" ((?<=\|\|) being a positive lookbehind).

answered Oct 20, 2019 at 22:49

Cary Swoveland

111k6 gold badges69 silver badges105 bronze badges

Collectives™ on Stack Overflow

Regex - capture multiple groups and combine them multiple times in one string

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related