NetNews Usenet Archive 1993 #3/NN_1993_3.iso/spool/comp/editors/3265

Text File | 1993-01-21 | 2.9 KB | 72 lines

Newsgroups: comp.editors
Path: sparky!uunet!munnari.oz.au!metro!physiol.su.OZ.AU!john
From: [e-mail] (John Mackin)
Subject: Re: A little question on vi
Message-ID: <[e-mail]>
Summary: vi is a _text_ editor
Sender: [e-mail] (John Mackin)
Organization: Chickenhawk Software
References: <[e-mail]>
Date: Thu, 21 Jan 1993 15:05:05 GMT
Lines: 59

In article <[e-mail]>,
    [e-mail] (Simon Ho Ki CHAN) writes:

>    Hi, is there anybody who knows how to put the EOF marker at the end of
> the last line, instead of putting it in a new line? e.g I wanna create a file
> like the following
>
>        blah, blah
>        blah, blah<EOF>
>
>    instead of
>
>        blah, blah
>        blah, blah
>        <EOF>

Someone has made this point already, but I have a few things to add.

The answer to the question is that this is impossible with vi.  And
as `someone' (what I wouldn't give for a better news-reading
interface!) pointed out, there is no "EOF marker" in a UNIX file.
A UNIX file is an exact number of characters (bytes, octets)
long and therefore has no requirement for an "EOF marker" such as is
needed on some filesystems where files don't have an exact
length in bytes, but only a sector or block count.  (Note,
all my remarks here apply to UNIX.  If the original poster
is using vi on something else, all bets are off.)

There is a good reason why this is impossible.  The reason is that
vi is a text editor, for editing text files.  A well-formed UNIX
text file consists of zero or more lines.  A line consists of
zero or more non-null characters followed by a terminating
newline character.  Hence, a non-empty file with no terminal newline
is not a well-formed UNIX text file.  You don't want to
create one of those, since (unfortunately) far too many
UNIX tools will behave in `interesting' ways when presented
with one of them.  Similarly, you don't want to treat files
with embedded nulls as text -- I'll never forget the day grep
failed to match patterns that were indeed matched by strings
in the file, because the file also had nulls in it.

(There is also a well-known bug in many versions of vi to do
with this.  The above definition of a text file certainly
admits the null (that is, zero-length or empty) file as a
valid text file, as it must.  Unfortunately, many versions
of vi don't allow you to create the null file, or indeed
operate on it sensibly.  You can read it in, but it immediately
becomes a one-line file.)

This is not to say that a text editor _mustn't_ let you
create a file without a terminal newline.  Indeed, I tend
to come down on the side of never second-guessing the user.
But, I can see where the idea came from, and it's not
wholly without merit.

--
John Mackin <[e-mail]>
Knox's box is a 286.                 Fox in Socks does hacks and tricks
Knox's box is hard to fix.           To fix poor Knox's box for kicks.