[TUHS] FD 2

[Jon Steinhart]

ron minnich writes:
> I am trying to remember when fd 2 (aka stderr) became a thing. I have a
> vague memory that it was post-v6 but that may be way off.

Related to this, according to Steve Johnson, stderr was not part of the
original stdio library; it was added as a side effect of the development
of troff for the C/A/T photoypesetter which projected images onto silver
photographic paper. That became very expensive when the Hunt brothers
cornered the silver market, and folks were asked to cut down on
phototypesetter use. It was not uncommon to send a job to the typesetter
only to get back a beautifully formatted page containing a cannot open
file error message. The stderr file pointer was born so that error messages
could go to the terminal instead of to the typesetter in order to save money.