Regular expression - check comma separated sub strings length

Question

I am new to regular expression. My input is a string with comma. I need to validate each sub string length is 3 which is split by comma. example: "em1,erg,123,enc" Here sub strings length is 3, so it is valid. If "em1,erg,123,ency", It should be invalid. How to validate in regular expression without any other code?

Answer 1

You can use the following regular expression:

^(?:[^,]{3},)*[^,]{3}$

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It consists of the following parts:

• ^ - beginning of the string
• [^,]{3} - exactly three characters not being a comma
• , - a comma
• (?: ... )* - the former wrapped in a (non-capturing) group followed by a *, which lets the contained pattern repeat (zero or more times).
• [^,]{3} - exactly three characters not being a comma. This is necessary to match the last three characters (which do not have a comma at the end)
• $ - end of the string