Undocumented feature in Sys5: synchronous write

[Doug Gwyn]

trouble(1) seems to be one of the things that the UNIX System V
(Release 1) blurbs advertised but that were not delivered to customers
outside the Bell System (like se, nsc, x25*, ...).

trenter(1) has been promised to us by AT&T so many times as part
of UNIX System V Release 2.0 that they will look really silly if
they withhold it, too.