In French, sacrebleu or sacredieu is always written as one word without accent, the 'e' in the middle being pronounced like a faint and short 'eu' . In English, the phrase is often written with two words: sacre bleu.
Even though present in modern french-language dictionaries, the phrase is not in use in everyday conversation at all anymore.
It is often considered in the English-speaking world as a quintessential French phrase, even though it is not Written with two words (sacre bleu!), it has been popularized by Agatha Christie's Belgian hero Hercule Poirot. The word is also occasionally used by French people depicted in American cartoons. In the popular old comic book, Blackhawk, the phrase is Andre the Frenchman's favorite oath.
Sacrebleu is also used in several recent Disney movies depicting French characters, including The Aristocats, The Little Mermaid (1989 film) and Beauty and the Beast.