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From: John Mackin <john@syd.dit.csiro.au>
Date: Fri, 23 Aug 1991 19:15:43 -0500
To: The rc Mailing List <rc@archone.tamu.edu>
Subject: Re: early reaction(s) to rc
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Arnold writes, in relation to rcmain:

    I would love to know how this works.  -c is trivial:

    	eval $*(2) ; exit

    and so is -l, but -p and -i are harder --- is there some secret equivalent
    of `set' in his rc?  In other words, how does the rc program tell the
    shell itself what to do with the environment and whether or not to prompt?

I second the first comment; for quite a while I've wanted to have a look
at a real Tenth Edition (as opposed to Plan 9, if there is a difference)
rcmain.  Boyd, do you reckon if you ask td to mail you one, he will?  I
have some general comments to make about rcmain which I will send later
today, right now I have to get off to work -- but I just thought I should
point out that -p doesn't require any support beyond what our rc already
has:

eval `{ whatis | rev | sed -n -e '/ nf$/s/^.*{\(.*\)$/\1/p' | rev }

You can't really do without the two rev's, since there's no way to be
sure your r.e. is matching the function name correctly if you try that
(consider that function names, if quoted, may contain both space and
left-curly-bracket).  But that certainly does the job of removing
functions from the environment.  (Of course, in a real rcmain, all
the commands above -- eval, whatis, rev, sed, and rev -- would be
prefixed by `builtin' to avoid being subverted by functions before
they could accomplish the task of deleting them.  I have omitted this
here for clarity.)

OK,
John.