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Path: utzoo!linus!philabs!cmcl2!seismo!mcvax!ukc!stc!iclbra!wja
From: wja@iclbra.UUCP (Wayne Alston)
Newsgroups: net.bugs.usg
Subject: fun bug in vi
Message-ID: <124@iclbra.UUCP>
Date: Thu, 23-May-85 02:52:04 EDT
Article-I.D.: iclbra.124
Posted: Thu May 23 02:52:04 1985
Date-Received: Fri, 24-May-85 22:26:34 EDT
Distribution: net
Organization: I.C.L., Lovelace Road, Bracknell, Berkshire.
Lines: 23
Xpath: stc stc-a


An undocumented feature in vi allows a valid command in the file being 
'edited' of the form

	...ex:{command}:
or
	...vi:{command}:

to be actioned before interactive editing is allowed.  However, the bug also 
permits the variants ei and vx. The code reads:-

	if (beg[-2] != 'e' && beg[-2] != 'v') return;
	if (beg[-1] != 'x' && beg[-1] != 'i') return;

in routine checkmodeline().

The bug was discovered by trying to install a user with the initials 'jei' into
/etc/passwd.

Note that the above structure need not be at the beginning of the file.
Try vi'ing a file containing ei:x: .

Wayne Alston
..!reading!iclbra!wja