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From: bostic@toe.CS.Berkeley.EDU (Keith Bostic)
Newsgroups: comp.editors,comp.unix.bsd
Subject: Re: Obscure (to me, at least) bug in vi
Date: 24 Jan 1995 17:46:26 GMT
Organization: University of California, Berkeley
Lines: 48
Distribution: inet
Message-ID: <3g3edi$8it@agate.berkeley.edu>
References: <3f79vk$5c@darkstar.UCSC.EDU> <3g25g9$avc@griffin.itc.gu.edu.au>
NNTP-Posting-Host: toe.cs.berkeley.edu
In article <3g25g9$avc@griffin.itc.gu.edu.au>,
Tony Nugent <haynes@cats.ucsc.edu> wrote:
>
>haynes@cats.ucsc.edu (James H. Haynes) writes:
>
>I have a user who gets into those dark, cobwebby corners of vi.
>Here's a bug he reported to me.
>
>Make a .exrc file containing the line
> map _ /-$(esc)JxX
>where (esc) is the escape character.
>
>Make a test file containing the likes of
>
>aaaa-
>aaaaa
>bbb-
>bbbbbb
>
>and edit it. The thing in the .exrc file maps the underbar character to be
>an end-of-line-hyphen remover. You'll see that it works.
>
>Now try S to substitute something for the whole line. You'll find on
>some versions of vi that the characters in the macro get stuck into the
>line you are editing; specifically it will contain JxX- before you type
>anything further.
What's going on is that vi has the following internal mappings:
A to $a
I to ^i
C to c$
S to c_
Y to y_
A and I are safe; in the case of C, S, and Y, however, the
mappings are done by changing the current command character,
and pushing the operator ($, _ and _, respectively) onto the
queue of input keys. While I haven't proven this, my belief
is that those keys are subjected to map expansion, resulting
in the behavior your user saw.
I also believe, but haven't proven, that you can get similar
behavior with the P/p commands, if the a/i keys are mapped.
Keith Bostic
bostic@cs.berkeley.edu