From owner-freebsd-questions@FreeBSD.ORG Tue Sep 25 17:09:14 2007 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3786F16A417 for ; Tue, 25 Sep 2007 17:09:14 +0000 (UTC) (envelope-from kline@tao.thought.org) Received: from tao.thought.org (dsl231-043-140.sea1.dsl.speakeasy.net [216.231.43.140]) by mx1.freebsd.org (Postfix) with ESMTP id F365D13C48A for ; Tue, 25 Sep 2007 17:09:12 +0000 (UTC) (envelope-from kline@tao.thought.org) Received: from tao.thought.org (localhost [127.0.0.1]) by tao.thought.org (8.13.8/8.13.1) with ESMTP id l8PH8sGJ057092; Tue, 25 Sep 2007 10:08:55 -0700 (PDT) (envelope-from kline@tao.thought.org) Received: (from kline@localhost) by tao.thought.org (8.13.8/8.13.1/Submit) id l8PH8qVq057087; Tue, 25 Sep 2007 10:08:52 -0700 (PDT) (envelope-from kline) Date: Tue, 25 Sep 2007 10:08:51 -0700 From: Gary Kline To: Giorgos Keramidas Message-ID: <20070925170851.GE50519@thought.org> References: <20070925013723.GA50027@thought.org> <46F87B68.6090607@queue.to> <20070925035217.GC50519@thought.org> <20070925162424.GA13463@kobe.laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070925162424.GA13463@kobe.laptop> User-Agent: Mutt/1.4.2.2i X-Organization: Thought Unlimited. Public service Unix since 1986. X-Of_Interest: With 21 of service to the Unix community. Cc: Howard Goldstein , Gary Kline , freebsd-questions@freebsd.org Subject: Re: sed question... X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 25 Sep 2007 17:09:14 -0000 On Tue, Sep 25, 2007 at 07:24:25PM +0300, Giorgos Keramidas wrote: > On 2007-09-24 20:52, Gary Kline 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,$d:wq'' ... > > sed -i '' -e '31,$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