The docs for readf() say: Formatted read one line from stdin. However, this function doesn't read a whole line as the text implies. Or at least I hope it doesn't. It would be better to say it extracts characters from the file using format.readFormatted().
Also, I assume the return value is the one generated by readFormatted(), but it should be explicitly stated.
https://github.com/D-Programming-Language/phobos/pull/459