From owner-freebsd-questions@FreeBSD.ORG Mon Jul 7 08:44:09 2014 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 56FF7172 for ; Mon, 7 Jul 2014 08:44:09 +0000 (UTC) Received: from mx01.qsc.de (mx01.qsc.de [213.148.129.14]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 19C112B46 for ; Mon, 7 Jul 2014 08:44:08 +0000 (UTC) Received: from r56.edvax.de (port-92-195-69-249.dynamic.qsc.de [92.195.69.249]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx01.qsc.de (Postfix) with ESMTPS id 249CE3CD71; Mon, 7 Jul 2014 10:44:04 +0200 (CEST) Received: from r56.edvax.de (localhost [127.0.0.1]) by r56.edvax.de (8.14.5/8.14.5) with SMTP id s678i3W7003338; Mon, 7 Jul 2014 10:44:03 +0200 (CEST) (envelope-from freebsd@edvax.de) Date: Mon, 7 Jul 2014 10:44:03 +0200 From: Polytropon To: Arthur Chance Subject: Re: The name "grep" Message-Id: <20140707104403.5a0694ff.freebsd@edvax.de> In-Reply-To: <53BA4F77.60907@qeng-ho.org> References: <20140707075443.d47ca06a.freebsd@edvax.de> <53BA4F77.60907@qeng-ho.org> Reply-To: Polytropon Organization: EDVAX X-Mailer: Sylpheed 3.1.1 (GTK+ 2.24.5; i386-portbld-freebsd8.2) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: FreeBSD Questions X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 07 Jul 2014 08:44:09 -0000 On Mon, 07 Jul 2014 08:42:47 +0100, Arthur Chance wrote: > From ancient memory circa 1980, probably suffering from bit rot: > > Before grep existed, to use ed to print lines in a file that match a > particular regular expression > > ed $file > g/re/p > q > > where the "re" stands for the regular expression and you're applying the > "p" (print) command to each line that matches it. Yes, I already thought this was related to ed (discussed in the same book at a previous occassion, and refered to as "the editor", prior to introducing vi). So "r" and "e" aren't acutual commands (p is a command, "print", g a modifier, "global"), but refers to "put regular expression here". Having another seizure that forced me to read "man ed", I found some "re" entries: (.,.)s/re/replacement/ (.,.)s/re/replacement/g (.,.)s/re/replacement/n \(re\) The two important entries are: (1,$)g/re/command-list Apply command-list to each of the addressed lines matching a reg- ular expression re. The current address is set to the line cur- rently matched before command-list is executed. At the end of the g command, the current address is set to the last line affected by command-list and (.,.)p Print the addressed lines. The current address is set to the last line printed. There is the "re" of "g/re/p", leading to the understanding what "grep" basically means (even though it offers much more functionality as a stand-alone tool, of course). > When a newbie asked how to print matching lines in a file, you'd answer > "grep" and show them the trick, and eventually the name got given to the > grep program when it was written. I think the "global regular expression > print" explanation is based on explaining what the original ed command did. And I have actually _tried_ that with /bin/ed - it works! So should the "grep" manpage (and maybe other manpages, too) contain a hint on where the program name originates from? In my opinion, this would be a good place to put such kind of information because manpages are a "condensed form" of wisdom, available locally, for reference, study, and overall education. Global Real Education, Pal. ;-) -- Polytropon Magdeburg, Germany Happy FreeBSD user since 4.0 Andra moi ennepe, Mousa, ...