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How can I write a regex expression that checks a certain numeral at a certain place?

For example, if I want to have regex for only numerals, length 7 - I will write something like

^[0-9]{7}$

But how can I make that the 4th digit is always 1?

Example:

0031000 true

9991999 true

9992999 false
totok
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dimmxx
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1 Answers1

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You can use this regex to capture two parts of number, before and after digit one:

^\d{3}(?:1)\d{3}$

Using (?:1) (a non-capturing group) mean you need find digit one but dont want capture this. On the final result you get only ^\d{3} and \d{3}$.

Sergio Cabral
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