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

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:

No Match:

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...

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.

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

来源：https://stackoverflow.com/questions/65922591/regex-for-a-permutation-of-exactly-7-digits-and-2-hyphens-without-2-consecutive

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