regex - Regular Expression to Match List of File Extensions

Question

I would like to have a regular expression that will match a list of file extensions that are delimited with a pipe | such as doc|xls|pdf This list could also just be a single extension such as pdf or it could also be a wild card * or ? I would also like to exclude the | at the start or the end of the list and also not match the <>/:" characters.

I have tried the following but it doesn't account for a single * wildcard.

^([^|\<>/:"]|[^\<>:"])[^/\<>:"]*[^|/\<>:"]$

I have been on one of the online testers but can't seem to get over the final hurdle. If someone could point me in the right direction I would be most grateful.

Answer 1

You can construct this from smaller building blocks. A single extension, excluding the characters you mention, would be:

[^\<>/:"]+

We should probably also exclude | since that's our delimiter:

[^\<>/:"|]+

This can automatically match wildcards as well, since they're not forbidden.

To construct the |-separated list from those is then easy:

[^\<>/:"|]+

followed by an arbitrary number of the same thing with a | before that:

[^\<>/:"|]+(|[^\<>/:"|]+)*

And if you want a complete string to match this, add the ^ and $ anchors:

^[^\<>/:"|]+(|[^\<>/:"|]+)*$