匹配以9位开头并可能以字符串结尾的字符串

Question

I am basically trying to match a 10 character ISBN, so far I am able to match any string that is 10 characters long but it is not accurate at identifying the string as an ISBN

A 10 character long isbn can have 9 starting digits and end with a letter or have 10-digits, e.g.

0273737025

027373702X

If the final character is a letter it will always be X

what I have so far

[a-zA-Z0-9]{10,10}

this regex will be able to extract an isbn from a string like

"asjdh - asd a -  dsa- 0273737025"  = 0273737025

but will also extract anything else that is 10 or more characters long

"asjdh - asd a -  dsa- myveryearly"  = myveryearl

Is there a regular expression that can meet these requirements?

Answer 1

\d{9}(?:\d|X)

This is 9 digits followed by either a digit or 'X'.