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Date: Mon, 8 Jul 1996 17:59:04 -0400 (EDT)
From: Dmitry Kohmanyuk <dk@dog.farm.org>
Message-Id: <199607082159.RAA09331@dog.farm.org>
To: mbarkah@hemi.com (Ade Barkah)
Cc: hackers@freebsd.org
Subject: Re: NFS install problem with 2.2-960612-SNAP, motd, etc.
Newsgroups: cs-monolit.gated.lists.freebsd.hackers
Organization: FARM Computing Association
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In article <199606200510.XAA19984@hemi.com> you wrote:
> rc.local has the following code in it:

> | T=/tmp/_motd ...
> | uname -v | sed ...  > $T
> | ...
> | cp $T /etc/motd

> The above is extremely annoying. =-) Is there a good reason to keep 
> such code in rc.local ? Can we get rid of it ? Please ? =-) I can
> just think of all the poor FreeBSD newcomers who can't for the life 
> of them figure out why their /etc/motd keeps on dissappearing. Over-
> writing user files is morally bad, anyways.

it is not disappearing;  there is just some little magic insisting on giving
user an idea of the system s?he have just logged in ;-)

I would comment on it line-by-line:
T=/tmp/_motd		# a name for the scratch file
rm -f $T		# delete it
uname -v | sed -e '...[long]...' > $T	# put massaged uname output to it
echo "" >> $T		# append a line to it
sed '1,/^$/d' < /etc/motd >> $T	# append old motd but its begginning
			# up to the first empty line to it
cp $T /etc/motd		# copy it back to /etc/motd
chmod 644 /etc/motd	# fix perms
rm -f $T		# remove scarch file

the only bad possibility arising from this is:
when you put something into /etc/motd and _remove_ first FreeBSD id line,
all text from the beginning of /etc/motd to the first empty line 
(or to the end of file, if there isn't an empty line there) 
would be replaced.  (if file starts with empty line, text until _second_
empty line would be lost.)

I can consider this a suboptimal behaviour, though.  
(Should we put `Do not remove this tag under penalty of law' into 
  manual page for /etc/motd? <grin> )

changing 
sed '1,/^$/d'
to
sed '/^FreeBSD /,/^$/d'

can probably make anyone happy, though.

--
"'Programming' is a four-letter word."  --Craig Bruce