Regex for a permutation of exactly 7 digits and 2 hyphens, without 2 consecutive hyphens

user_11675928 0
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I a looking for a Regex to match a string which should:

  • start with a digit
  • 'in-between' have a permutation of exactly 7 digits and 2 hyphens, without 2 consecutive hyphens
  • end with a sequence of digit, hyphen, digit

Match:

  • 01-234-5678-9
  • 01234-56-78-9
  • 0123-4-5678-9
  • 012-345-678-9
  • 01-234567-8-9
  • 01-234-5678-9
  • 0-12345-678-9
  • 0-123-45678-9
  • 0-123-45678-9
  • 01-23456-78-9
  • 0-123456-78-9
  • 0-1234567-8-9

No Match:

  • 01-234-56789-0
  • 01-234-567-8
  • 01--2345678-9
  • 01-2345678--9
  • 0-1-23456789
  • -01-2345678-9

For now, I could not quite figure out how to match the 2 'in-between' hyphens: ^\d\d{7}\d-\d$

EDIT: Thanks to the answers I had to this question, I was able to expand it to this other question regarding ISBN-10 and ISBN-13...

regex
2 Answers

You can assert 7 digits and the digit - digit part at the end.

For the match there should be at least a single digit before and after the hyphen to prevent consecutive hyphens.

^\d(?=(?:-?\d){7}-?\d-\d$)\d*-\d+-\d*\d-\d$

  • ^ Start of string
  • \d Match a single digit
  • (?= Positive lookahead
    • (?:-?\d){7} Match 7 digits separated by an optional -
    • -?\d-\d$ Match an optional - and the \d-\d$ at the end
  • ) Close the lookahead
  • \d*-\d+-\d*\d-\d Match possible formats where all hyphens are separated by at least a single digit
  • $ End of string

Regex demo

user_54249880

My two cents:

^(?=.{11}-\d$)(?:\d+-){3}\d

See the online demo

  • ^ - Start string anchor.
  • (?= - Open positive lookahead:
    • .{11}-\d$ - Any character other than newline 11 times followed by a hypen, a single digit and the end string anchor.
    • ) - Close positive lookahead.
  • (?: - Open non-capture group:
    • \d+- - 1+ digit followed by an hyphen.
    • ){3} - Close non-capture group and match three times.
  • \d - Match a single digit.

I guess alternatively even ^(?=.{13}$)(?:\d+-){3}\d$ would work.

user_97581940
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