These days, it’s no longer good enough to use local phone number formats for your address book; you might be trying to dial someone via SIP without any clear locale information, for example, and so trying to dial a 10-digit US number might end up routing the call to some other country, which can be quite embarrassing.
Further, in this day and age, you might actually be travelling between different countries, and so you can’t really predict what your outgoing call routing will be like!
So, here’s a really simple C++ program that wraps libphonenumber to normalize the phone numbers in a .vcf file (used by most modern address book systems) based on your current locale. It can be used both on local .vcf stores as well as ones stored on a CardDAV/CalDAV server.
See the code comments for usage details.