From owner-freebsd-questions@FreeBSD.ORG Tue Sep 25 03:52:18 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 7380816A419 for ; Tue, 25 Sep 2007 03:52:18 +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 0D72513C457 for ; Tue, 25 Sep 2007 03:52:17 +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 l8P3qHeb051257; Mon, 24 Sep 2007 20:52:18 -0700 (PDT) (envelope-from kline@tao.thought.org) Received: (from kline@localhost) by tao.thought.org (8.13.8/8.13.1/Submit) id l8P3qHMf051256; Mon, 24 Sep 2007 20:52:17 -0700 (PDT) (envelope-from kline) Date: Mon, 24 Sep 2007 20:52:17 -0700 From: Gary Kline To: Howard Goldstein Message-ID: <20070925035217.GC50519@thought.org> References: <20070925013723.GA50027@thought.org> <46F87B68.6090607@queue.to> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <46F87B68.6090607@queue.to> 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: 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 03:52:18 -0000 On Mon, Sep 24, 2007 at 11:07:20PM -0400, Howard Goldstein wrote: > Gary Kline wrote: > > My earlier post about deleting the first N lines was answered by > > this one-liner site {below}. I wasn't including any > > redirection; doing so finally resolved the problem. Now I need > > to delete every line from the 19th or so to the last line. > > Question one, can anybody explain the following syntax? What do > > "P", "D" "ba" represent, in other words? > > > > > > # delete the last 10 lines of a file > > sed -e :a -e '$d;N;2,10ba' -e 'P;D' # method 1 > > sed -n -e :a -e '1,10!{P;N;D;};N;ba' # method 2 > > > > > > Question two, can sed do its thing inline? > > Wouldn't it be easier to use head -n 18 ? > No, because most of these files are between 40 and 50 lines. I only care about the first 30 or 40; everything below has to be deleted. By hand, using vi, I might type :31,$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. -- Gary Kline kline@thought.org www.thought.org Public Service Unix http://jottings.thought.org http://transfinite.thought.org