On Fri, Nov 25, 2022 at 01:58:55PM +0900, Junio C Hamano wrote:

Jeff King [off-list ref] writes:

quoted

One thing I'd worry about is buffering. One of the nice things about
"-v" is that there is nothing between you and the running programs, so
you are much less likely to be fooled about the order of events in the
output. Or wondering why nothing is happening because real-time output
seems to have stalled. But piping through "cat" may end up with weird
pauses while it fills up a 4k buffer. Using stdbuf could help, but
that's far from portable.

We could pipe to "dd bs=1 conv=fsync" (tongue-in-cheek---I think
conv=fsync is a GNU thing).

We don't need the fsync; we are just worried about in-process buffering,
not kernel-level flushing. So bs=1 is sufficient, in that it would
use syscalls to read/write single bytes. It would just be horribly
inefficient.

We really just want immediate partial read()/write() but with sensible
buffer sizes. It would be easy to write a 5-line C program that did this
if we really wanted to. I'm not entirely convinced it's worth worrying
too much about, though.

-Peff