If openBinaryTempFile is used in this way a few times in a row, it returns the same file name every time.
A quick inspection of the [source code][1] reveals that it uses the process ID (PID) to generate the initial filename of the temporary file. If the file already exists, the number is incremented until a new file is created. So the current implementation does in fact have this predictable behavior. I don't *think* this is insecure (but don't quote me on that), since `O_EXCL` is used to create the file, but it may be somewhat inefficient if there are a many files being created by one process or if processes with similar IDs create temporary files with this method. [1]: http://hackage.haskell.org/package/base-4.7.0.2/docs/src/System-IO.html#line...