How to match the coupled string with regular expression?

Question

I want to match this kind of format:

AA sysodufsoufdds AA

Where AA can be arbitary consecutive string with no space in it.

Is there a solution?

Answer 1

How about

AA.*?AA

or to match whole string

^AA.*?AA$

Answer 2

How about this:

   ^(\w+).*?\1$

This will match any char sequence followed by anything followed by same char seq at the front. So it'll match:

AA sysodufsoufdds AA
BBB sysodufsoufdds BBB
ABC sysodufsoufdds ABC

Answer 3

This matches a chunk of characters followed by a space followed by anything followed a space followed by the first chunk of characters...

([A-Z0-9]+) .* \1

There are a number of different ways of matching these bits. The key thing is the use of \1, which is a backrefrence to the first defined pattern. If you had two patterns you could use \2 to refer to the second one. For instance this ...

([A-Z0-9]+) (.*) \1 \2

... would match this string

AA sysodufsoufdds AA sysodufsoufdds