vi bug?

[Daniel R. Levy]

I have found what I _think_ is a bug in several different versions of vi
(on a VAX running BSD4.1, on a 3B2/400 running SysVR2, on a 3B20S running
SysVR2, but not on a PDP 11/70 running the UNIX 4.0 system).

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.

For example, a file containing the two lines

ex::
ex:3:

will, when read into some versions of vi, produce the diagnostic
"Not that many lines in buffer."

This problem arose when using vi to edit ASCII database files structured into
newline-separated records with the fields separated by colons (a la
/etc/passwd) and where 'ex' was one possible entry in the first field of
a record.

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.
-- 
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