REGEX Repeater "Or" Operator - regex

Question

I am looking to match a regex with either 2 [0-9] repeats (and then some other pattern)
[0-9]{2}[A-z]{4}
OR 6 [0-9] repeats (and then some other pattern)
[0-9]{6}[A-z]{4}
The following is too inclusive:
[0-9]{2,6}[A-z]{4}
QUESTION
Is there a way that I can specify either 2 or 6 repeats?

Answer 1

You can use the or | like this within a non-capturing group:
(?:[0-9]{2}|[0-9]{6})[A-z]{4}
Be aware that using [A-z] doesn't only include lower and upper case letters, but also [, \, ], ^, _, and ' which lie between Z and a in the ASCII code points. Use [A-Za-z] for letters, as pointed out by #AlanMoore in his comment.

Answer 2

This should work
(?:[0-9]{2}|[0-9]{6})[a-zA-Z]{4}
Do you have some test cases I can verify it with.
12asdf - passes
123456asdf - passes
1234asdf - fails
However, if you don't anchor the start of the regex to a word (\b) or line boundary (^), the 1234asdf will have 34asdf as a partial match.
So either
\b(?:[0-9]{2}|[0-9]{6})[a-zA-Z]{4}
or
^(?:[0-9]{2}|[0-9]{6})[a-zA-Z]{4}
As a quick rundown of the regex changes
(?: ) creates a non capturing group
| selects between the alteratives [0-9]{2} and [0-9]{6}
^ matches the start of a line
$ matches the end of a line
\b matches a word boundary
[a-zA-Z] is being used instead of [A-z] as it's likely what was intended (all alpha characters, regardless of case)
You can also replace your [0-9]s with a \d which is shorthand for any digit. The best way I can think of to right this, and not get partial matches is as follows
(?:\b|^)(?:\d{2}|\d{6})[a-zA-Z]{4}(?:\b|$)

Answer 3

The classic way would be:
(?:[0-9]{2}|[0-9]{6})[A-z]{4}
[Literally as [0-9]{2} OR [0-9]{6}]
But you can also use this one, which should be a little more efficient than the above with less potential backtracking:
[0-9]{2}(?:[0-9]{4})?[A-z]{4}
[Here, [0-9]{2} then potential other 4 [0-9] which makes a total of 6 [0-9] in the required conditions]
You might not be aware that [A-z] matches letters and some other characters, but it actually does.
The range [A-z] effectively is equivalent to:
[A-Z\[\\\]^_`a-z]
Notice that the additional characters that match are:
[ \ ] ^ _ `
[spaces included voluntarily for separation but is not part of the characters]
This is because those characters are between the block letters and lowercase letters in the unicode table.

Answer 4

Not obvious, but yes:
(?:\d{2}|\d{6})