Change the system language/locale in Mac OS X Terminal
Change the current system locale/language without going to ▹ System Preferences ▹ Language & Text ▹ Language & Region in Mac OS X:
Get the current locale:
defaults read -g AppleLocale
Get the current language:
defaults read -g AppleLanguages
Get a list of the user’s language preferences:
defaults read NSGlobalDomain AppleLanguages
Mac OS X will use the languages in decreasing order of preference (if the first one is not available in a particular app).
Change language/locale to English (Australia):
defaults write NSGlobalDomain AppleLanguages "(en-AU)"
Open Safari in English (Australia):
/Applications/Safari.app/Contents/MacOS/Safari -AppleLanguages '(en-AU)'
Tip: Press ↑ to navigate in your bash history to change the system and Safari language as many times as you want without typing the whole command again.