How to write incrementally to a text file and flush output

My Node.js program - which is an ordinary command line program that by and large doesn't do anything operationally unusual, nothing system-specific or asynchronous or anything like that - needs to write messages to a file from time to time, and then it will be interrupted with ^C and it needs the contents of the file to still be there.

I've tried using fs.createWriteStream but that just ends up with a 0-byte file. (The file does contain text if the program ends by running off the end of the main file, but that's not the scenario I have.)

I've tried using winston but that ends up not creating the file at all. (The file does contain text if the program ends by running off the end of the main file, but that's not the scenario I have.)

And fs.writeFile works perfectly when you have all the text you want to write up front, but doesn't seem to support appending a line at a time.

What is the recommended way to do this?

via rwallace