Finding a DOI in a document or page

Question

The DOI system places basically no useful limitations on what constitutes a reasonable identifier. However, being able to pull DOIs out of PDFs, web pages, etc. is quite useful

Answer 1

The following regex should do the job (Perl regex syntax):

/(10\.\d+\/\d+)/

You could do some additional sanity checking by opening the urls

http://hdl.handle.net/

and

http://dx.doi.org/

where is the candidate doi,

and testing that you a) get a 200 OK http status, and b) the returned page is not the "DOI not found" page for the service.