Conventional wisdom says that appending to a file is atomic, up to a certain write size. That means, for example, that you can have multiple processes write shared a log file and not have the log output crossed. Recently, I was thinking about this “conventional wisdom” and decided to look for some proof. After some Googling, and eventually landed on this StackOverflow question which discusses the question at hand. The accepted answer has a lot of good information, but also uses the words “supposed to be” and “assuming” a little to much to be conclusive.