. helps debugging output; you can see the difference
between parent and child easily (it's sometimes
confusing to see an expected endpoint number with
an unexpected name, i.e. before exec())
. when processes crash after fork and before exec, it's
an instant hint that that's what's going on, instead of
it being the parent (endpoint numbers don't usually convey
this)
. name returns to 'normal' after exec(), so *F isn't visible
normally at all. (Except for for RS which forks apparently.)