It's a combination of many things. You're probably writing to a file buffered, but terminal writes are generally unbuffered. In addition, I had a terminal setup once that just did a poor job of displaying text (line wrapping was slow, perhaps) and programs that would write out to stdout would be slow.

> printing to stdout is much, much, much, much slower than printing to a file

False dichotomy. stdout can very well be a file. What you mean is that printing to a terminal is slower than to a file.

True enough.

2>&1>/dev/null

blocking. blocking. blocking. blocking. rtfm

Again, the problem is not that writing to file descriptors is blocking. The problem is that writing to the screen is very slow. Writing to a file is just as blocking, but you'll block for much less time, because writing to a file is not slow.