Date: Tue, 25 Sep 2007 10:08:51 -0700 From: Gary Kline <kline@tao.thought.org> To: Giorgos Keramidas <keramida@ceid.upatras.gr> Cc: Howard Goldstein <hg@queue.to>, Gary Kline <kline@tao.thought.org>, freebsd-questions@freebsd.org Subject: Re: sed question... Message-ID: <20070925170851.GE50519@thought.org> In-Reply-To: <20070925162424.GA13463@kobe.laptop> References: <20070925013723.GA50027@thought.org> <46F87B68.6090607@queue.to> <20070925035217.GC50519@thought.org> <20070925162424.GA13463@kobe.laptop>
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On Tue, Sep 25, 2007 at 07:24:25PM +0300, Giorgos Keramidas wrote:
> On 2007-09-24 20:52, Gary Kline <kline@tao.thought.org> wrote:
> >On Mon, Sep 24, 2007 at 11:07:20PM -0400, Howard Goldstein wrote:
> >>> # delete the last 10 lines of a file
> >>> sed -e :a -e '$d;N;2,10ba' -e 'P;D' # method 1
> >>> sed -n -e :a -e '1,10!{P;N;D;};N;ba' # method 2
> >>>
> >>> Question two, can sed do its thing inline?
> >>
> >> Wouldn't it be easier to use head -n 18 ?
>
> If you _know_ that the file has 28 lines, yes. If you don't,
> then itmay be tricky to 'guess' that -n 18 is the right option.
>
> > No, because most of these files are between 40 and 50 lines. I only
> > care about the first 30 or 40; everything below has to be deleted. By
> > hand, using vi, I might type :31,$d that fixes that one file. Of
> > course, I could simply edit in "19" for "10" above. It would be more
> > savvy to understand the sed syntax.
>
> You don't need to manually edit files with vi(1) if all you want to do
> is type ``:31,$d<RET>:wq<RET>'' ...
>
> sed -i '' -e '31,$d' file.txt
The catch is that I don't always know the linecount; the only
thing I have found--by examing ALL hundreds of files (briefly:)
--is that I was to delete the last 19 lines.
If sed can understand negative indexing, then would -e '-19,$d'
work? That would makr sense from a human standpoint; not sure
how that would fit the sed model, tho.
gary
>
--
Gary Kline kline@thought.org www.thought.org Public Service Unix
http://jottings.thought.org http://transfinite.thought.org
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