Date: Mon, 04 Sep 2023 16:39:25 +0200 From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@FreeBSD.org> To: Ede Wolf <listac@nebelschwaden.de> Cc: questions@freebsd.org Subject: Re: cut off last lines of a document Message-ID: <86edjet336.fsf@ltc.des.no> In-Reply-To: <a9b64c1d-02a6-45c1-aaed-85e4cf622776@nebelschwaden.de> (Ede Wolf's message of "Mon, 4 Sep 2023 08:53:58 %2B0200") References: <57be5495-97f8-4f22-9ae2-cd9712596e64@nebelschwaden.de> <uy2fdgobbejnhyctyyrbhgvhutuhtbzzxwg5wukdujyhw7h25u@74ujfxm5gjlk> <CAMtcK2qbc1jQHXJ%2Bwu0F62o6aDQKYAx3kYARuQFZLHS6DJktRg@mail.gmail.com> <a9b64c1d-02a6-45c1-aaed-85e4cf622776@nebelschwaden.de>
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Ede Wolf <listac@nebelschwaden.de> writes:
> Am 03.09.23 um 23:16 schrieb paul beard:
> > export COUNT=`wc -l /var/log/messages | tr -d -c '\n[:digit:]'` #
> > export WANT=`echo "$COUNT-3" | bc ` # subtract 3 (or however many)
> > head -$WANT /var/log/messages # display the remainder.
1) there is no need to export the variables
2) don't use backticks, use $() instead
3) if you use 'wc -l <foo' instead of 'wc -l foo' you don't need tr
3b) alternatively, use read: wc -l foo | read COUNT FILENAME
4) the shell can do the math for you: 'head -$((COUNT-3)) foo'
> Thanks, but the problem I currently see here, as with the suggestion
> of Archimedes earlier, I am currently not easily able to convert this
> into a feed from stdin.
Pipe-friendly pure shell solution:
drop_last_three() {
local a b c d
read a
read b
read c
while read d ; do
echo "$a"
a="$b"
b="$c"
c="$d"
done
}
DES
--
Dag-Erling Smørgrav - des@FreeBSD.org
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