I was hoping to do something like:
defaults read -g AppleLanguages | awk -F, '/[^(]/{print $1;exit}'
but if only one language is listed in "Preferred Languages", then defaults read -g AppleLanguages returns an error:
The domain/default pair of (kCFPreferencesAnyApplication, AppleLanguages) does not exist
It works fine if multiple languages are listed. Does anyone have a reliable way of determining the language selected for a given user in OS X?