🚀 go-pugleaf

> I have found what I _think_ is a bug in several different versions of vi
  ....
> The trouble seems to be that vi will intercept certain ASCII sequences in
> the input file on lines beginning with 'ex:' and will interpret them as if
> they were commands.
> 
> Would someone who is in the know please tell me whether this behavior is
> a bug or a "feature"?  I certainly cannot find any mention of it in what
> little documentation I have about vi (the SysV and BSD man pages on ex and
> vi, and a document called "An Introduction to Display Editing using Vi").
> Thank you in advance.

This is an semi-documented feature:  

	Mode lines are now supported.  Put a line containing
		ex: xxx :
	in the first or last 5 lines of the file, where xxx is any ex
	command you want executed when that file is read in.  To make
	other programs happy, it should probably be inside a comment. ----+
	You can use vi: as well as ex:.  (Note: no space allowed          |
	between the "ex" and ":".  The spaces around xxx are considered   |
	part of the command, and so are optional.)                        |
                                                                          |
                                              eg /* ex: autoindent : */ <-+

It was added in version 3.7 (October 16, 1981).  This and other goodies
are found in a file ex.news which comes with the vi src.  On my machine,
it was in /usr/src/cmd/vi/vax/ex.news which is a vax running SVR2.  I don't
know whether or not it is considered proprietary, otherwise I would have
posted it in its entirety.
-- 
Jim Webb             "Out of phase--get help"          ...!ihnp4!hropus!jrw

Thanks to the several people who wrote or posted to say that yes, this
(intercepting ex: or vi: [or ei: or vx: -- yuck] in the first or last few
lines of a file being read in) is an old, old "feature" allowing for auto-
configuration of vi, and that, yawn, it had been hashed over many many
times before on the net.  (Guess I have to get a copy of the compleat net
archives, then, so I won't appear stupid to the oldtimers.  Postpone those
backups, Joe, gotta mount a few dozen magtapes to grep for something :-). )

I sure would have preferred that this behavior wasn't the default, requiring
a command line option or environment variable to turn it on, or at the least
that it could be turned off by a command line option or something in the
$HOME/.exrc file.  In certain contexts, e.g. editing ASCII database files,
it stinks.  I particularly liked the message from the fellow who said that his
version of the vi source code deleted this "feature" by #ifdef SUICIDE
preprocessor directives.  (I have now found it, in the routine checkmodeline()
in ex_io.c.  Not the #ifdef SUICIDE directive, but rather the suicidal code.)

Dan

-- 
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|       dan levy | yvel nad      |  my own and are not at all those of my em-
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|        skokie, illinois        |
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