OK, the goal of this question is not strictly programming related but it is a question programmers can answer using programming tools, and programmers may find useful answers here. Bear with me.
I find changing the system language in Mac OS X a useful way to augment my learning of natural languages, eg French. However sometimes I find a menu item or dialog box in French that I can't understand and it's a bore to google the translation or change the system language back to English. But I know that the English translation is hidden away somewhere in the localisation file and maps somehow to the French phrase. So what I want to do is extract all the text from all the localisation files to develop a mapping of this phrase in English = that phrase in French so I can look it up easily.
I know that the localisation files are stored in something like Localizable.strings, lproj files and nib files but I can't make head or tail of how they are stored or how to work with them. I can program but I've never written anything in Xcode. All the information I can find is for Mac OS / iOS programmers to localise their software, not for hackers to extract already made localisation information.
How can I extract the foreign language information as plain text from Mac OS X system and 3rd party software localisation files? Thanks!