CODEWITHSUNDEEP
regexrepeat
vicdelacruz
vicdelacruz

Reputation: 45

Matching a full repeating pattern

I can't seem to figure out this regex https://regex101.com/r/cQ9nK8/38

These should match

This should not match

As you can see they match individually but not as a whole, I though this would work but it doesn't

(?:[[:alnum:]]+(?:\.\d+)*)*

Upvotes: 2

Views: 57

Answers (2)

The fourth bird
The fourth bird

Reputation: 163362

You might use a repeating pattern:

  • First match [[:alpha:]] followed by optional [[:alnum:]] (if the first of 2 parts separated by a dot should not start with a digit)

    This would match January

  • Followed by an optional part that matches digit

    That will match January.313

  • Optionally repeat a dot followed by the same pattern

    That will match the last 3 examples.

Pattern

^[[:alpha:]][[:alnum:]]*(?:\.[[:digit:]]+(?:\.[[:alpha:]][[:alnum:]]*\.[[:digit:]]+)*)?$

Regex demo

A version without the POSIX notation could be

^[a-zA-Z][a-zA-Z0-9]*(?:\.[0-9]+(?:\.[a-zA-Z][a-zA-Z0-9]*\.[0-9]+)*)?$
  • ^ Start of string
  • [a-zA-Z][a-zA-Z0-9]* Match a char a-zA-Z optionally followed by a-zA-Z and digits
  • (?: non capture group
    • \.[0-9]+ Match a . and 1+ digits
    • (?:\.[a-zA-Z][a-zA-Z0-9]*\.[0-9]+)* Optionally repeat matching . a char a-zA-Z optionally followed by a-zA-Z and digits, a dot and digits
  • )? Close group and make it optional
  • $ End of string

Regex demo

Upvotes: 2

JvdV
JvdV

Reputation: 75870

Here is my attempt:

^((?:^|\.)[A-Z][A-Z\d]*(?:$|\.\d+))(?1)*$

See the online demo

  • ^ - Start string ancor.
  • ( - Open 1st capture group/pattern.
    • (?: - Open non-capture group.
      • ^|\. - Start string or literal dot.
      • ) - Close non capture group.
    • [A-Z][A-Z\d]* - A single letter followed by zero or more letters or digits.
    • (?: - Open non-capture group.
      • $|\. - End string or literal dot.
      • ) - Close non capture group. ) - Close 1st capture group/pattern.
  • (?1)* - Repeat the capture group/pattern zero or more times.
  • $ - End string ancor.

I've use case insensitive matching btw.

Upvotes: 2

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