Question

Regex to test string for length and that it contains at least one period

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Updated October 6, 2023

asked on October 5, 2023

Hi. I need help figuring out a regex that would test a string to make sure it's at least 8 characters in length and has at least one period in it.

Sample values:

1000.1528.E1 - this one should pass the regex as it is at least 8 characters in length and has at least one period

1528.E1 - this would fail the regex due to length

1000,1528,E1 - this would fail the regex due to commas instead of periods

Thanks for any assistance!

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Answer

SELECTED ANSWER

replied on October 5, 2023

This doesn't look right to me, so I ran it on https://regex101.com/ which says that the ones that are supposed to match don't match. In particular, "\.$" means that the input needs to end with a period. This is a pretty tricky regex to write because for the length matching you don't care what the characters are, but you have a global requirement to satisfy. That is a case for a lookahead matcher. I think this works:

^(?=.*\.).{8,}$

(Disclaimer: I used Bard also)

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Replies

replied on October 5, 2023

Here's what Google Bard AI says:

The following regular expression will test a string to make sure it's at least 8 characters in length and has at least one period in it:

^.{8,}\.$

This regex can be broken down as follows:

^ matches the beginning of the string.
.{8,} matches any sequence of characters that is at least 8 characters long.
\. matches a single period.
$ matches the end of the string.

Here are some examples of how the regex would match different strings:

String | Match
------- | --------
1000.1528.E1 | Yes
1528.E1 | No
1000,1528,E1 | No

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SELECTED ANSWER

replied on October 5, 2023

^(?=.*\.).{8,}$

(Disclaimer: I used Bard also)

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replied on October 6, 2023

I wasn't able to get Craig's answer to work so I'll try this one today. Thanks!

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replied on October 6, 2023

Brian, your suggestion worked. I'm also checking out Bard to refine the regex further and it seems to be working pretty well. Thanks!

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Regex to test string for length and that it contains at least one period

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