Regex: extract numbers between text

Question

currently I'm using such regex "(\d{4}\b)" in order to extract the numbers. Test string "test 125456 b", so the extract result is "5456".

I wish to get the same result "5456" under the string "test125456b".

I tried to use following regex

((?<!\d)(\d{4})(?!\d))

but it works if only 4 digits (not more) are noted between letters.

So, the aim is:

• extract only digits from the text
• extract only specific number of digits In this case 4) even in the text is given more
• digits (in this case 4) should be extracted backwards

Solution 1

(\d{4}(?=[^\d]))

Use this. It'll look for 4 digits with a non-digit following.

Regex101

Solution 2

To get the last four digits.

\d{4}(?=\D*$)

• \d{4} match the four digit character.
• (?=\D*$) Only if the four digits are followed by a zero or more non-digit characters and the end of the line boundary.
• So this matches the last 4 digits.

Comments

[d0nut]

@maraca that's what I get for doing regex in the morning I guess xD

[Avinash Raj]

(?=[^\d]) equivalent to (?=\D)

[d0nut]

@AvinashRaj im so glad to hear that

[Avinash Raj]

@maraca no, (?=[^\d]) won't match the end of the line boundary but (?!\d) match the end of the line boundary.

[d0nut]

Could we move this discussion to chat or something? I really dont like my phone blowing up with notifications on the technicalities of using one capture group over another at work

[Simo Erkinheimo]

The OP, and future readers stumbling across this answer, might learn more if you could add some text explaining why this works.