Regular expression to match pipes with no sub-string between them

Question

Can somebody please share the regex to match only the Pipes with no sub string between them?

For example:

ABC, XYZ, |||,|||||, ||G|F|,1|2,||||, R|T|Y

I only want ||| and ||||| and |||| selected.

Thanks in advance for your help.

Edit:

Using the help of people in the comments below. I have a regex that partially works (?<=^|,\s)?(\|+)(?=,|,$)

However, this selects the | after F in sub string ||G|F|

Is there anyway to modify this regex to only select pipes between commas that do not have strings between them?

Answer 1

You haven't given the language you are using. If it supports \K, as does PCRE (PHP) and others, you extract substrings that match the following regular expression.

(?:^|,)[^,|]*\K\|{2,}(?=[^,|]*(?:,|$))

Demo

The regex engine performs the following operations.

(?:^|,)     # match start of string or ',' in a non-capture group
[^,|]*      # match 0+ chars other than ',' and '|'
\K          # forget everything matched so far
\|{2,}      # match 2+ '|'  
(?=
  [^,|]*    # match 0+ chars other than ',' and '|'
  (?:,|$)   # match a comma or the end of the string 
)           # end non-capture group 

Taken from the demo link, "\K resets the starting point of the reported match."

If you wish to match single pipes between commas (e.g, ,1|2,) change {2,} to +.

If \K is not supported but a capture group could be used the following regular expression could be used.

(?:^|,)[^,|]*(\|{2,})(?=[^,|]*(?:,|$))

Demo

The strings of interest are held in capture group 1 for each match.