Regex to match everything except this regex

Question

I think this is a simple thing for a lot of you, but I have a very limited knowlegde of regex at the moment. I want to match everything except a double digit number in a string.

For example:

TEST 22 KLO4567

QE 45 C2C

LOP 10 G7G400

Now I found out the regex to match the double digit numbers: \\d{2}

Which matches the following:

TEST 22 KLO4567

QE 45 C2C

LOP 10 G7G400

Now it seems to me that it would be fairly easy to turn that regex around to match everything BUT "\\d{2}". I searched a lot but I can't seem to get it done. I hope someone here can help.

Answer 1

This only works if your regex engine supports look behinds:

^.+?(?=\d{2})|(?<=\d{2}).+$

Explanation:

The | separates two cases where this would match:

• ^.+?(?=\\d{2})

This matches everything from the start of the string ( ^ ) until \\d{2} is encountered.

• (?<=\\d{2}).+$

This matches the end of the string, from the place just after two digits.

If your regex engine doesn't support look behinds (JavaScript for example), I don't think it is possible using a pure regex solution.

You can match the first part:

^.+?(?=\d{2})

Then get where the match ends, add 2 to that number, and get the substring from that index.

Answer 2

You are right rejecting a search in regex is usually rather tricky.

In your case I think you want to have [^\\d{2}] , however, this is tricky as your other strings also contain two digits so your regex using it won't select them.

I would go with this regex (using PCRE 8.36 but should work also in others):

\\*{2}\\w*\\*{2}

Explanation:

\\*{2} .... matches "*" literally exactly two times
\\w* .... matches "word character" zero or unlimited times

Answer 3

Found one regex pretty straightforward :

^(.*?[^\d])\d{2}([^\d].*?)$

Explanations :

• ^ : matches the beginnning of a line
• (.*?[^\\d]) : matches and catches the first part before the two numbers. It can contain anything (.*?) but needs to end with something different to a number ([^\\d]) so we ensure that there is only 2 numbers in the middle
• \\d{2} : is the part you found yourself
• ([^\\d].*?) : is the symetric of (.*?[^\\d]) : begins with something different from a number ([^\\d]) and matches anything next.
• $ : up to the end of the line.

To test this reges you can use this link

It will match the first occurence of double digit, but because OP said there was only one it does the job correctly. I expect it to work with every regex engine as nothing too complex is used.