Thanks for the bug report. It also seems to me that --line-buffered should apply 
to nulls, not newlines, when -z is used. Also, there are a couple of other 
places where stdout should get flushed after a newline. Perhaps we should use 
setvbuf instead (is it faster?) when -z is not also used, but right now I just 
want to get the bug fixed for the next release, so I installed the attached, 
more-conservative, patch, and am marking this bug as done.