>> magic sequence, but most Postscript interpreters _require_ this
>> magic sequence.

Umm, *no* postscript interpreters that I know of require it; dxpsview,
ghostscript, pageview, HP laser printer, apple laserwriter, dec laser
printer, a couple of other postscript laser printers, all treat the %!
as what it is: a comment, which happens to have a ! after it. By
market share, the HP laser printers alone probably account for "most
postscript interpreters" all by themselves :-)

Some spooling software does interpret the characters, and things like
pagereversal and n-up filters require %!PS-Adobe-n.m to indicate that
you are actually following the "document structuring conventions" that
let them *find* the page boundaries without actually interpreting the
code, but they are specifically *not* postscript interpreters...

This means that there is still some ambiguity in whether or not a file
"is" postscript. And you know, it *doesn't matter* as long as the user
has a choice about whether it *should be* interpreted as
postscript. (For various practical reasons, the default should
probably be to assume postscript since if you're wrong, you get one
error page and try again, whereas if you're wrong the other way, you
can waste hundreds of pages....)

Of course, I can't find the original message in this thread (and
there's no In-reply-to: in der Mouse's first message on the subject)
so I can't really figure out what we're debating here, beyond:

> I want to know how to:
> 1. Make a printer filter text into postscript, but leave postscript alone.

which I think we've covered [in that a %! guess using apsfilter would
work fine, and an always-raw or always-filter queue or use of
"nenscript" covers the exceptional cases.] I'd suggest further
comments go to the original poster, but der Mouse's posting doesn't
give any indication of who it was...
			_Mark_ <eichin@kitten.gen.ma.us>
			The Herd of Kittens