From: tmatimar@empress.com (Ted M A Timar) Newsgroups: comp.unix.questions,comp.unix.shell,news.answers Subject: Frequently Asked Questions about Unix (7/7) [Biweekly posting] Supersedes: Followup-To: comp.unix.questions Date: 20 Nov 1992 06:00:54 GMT Organization: Empress Software Lines: 263 Distribution: world NNTP-Posting-Host: pit-manager.mit.edu X-Last-Updated: 1992/10/21 Archive-name: unix-faq/part7 Version: $Id: part7,v 2.0 92/10/20 12:07:46 tmatimar Exp $ These seven articles contain the answers to some Frequently Asked Questions often seen in comp.unix.questions and comp.unix.shell. Please don't ask these questions again, they've been answered plenty of times already - and please don't flame someone just because they may not have read this particular posting. Thank you. These articles are divided approximately as follows: 1.*) General questions. 2.*) Relatively basic questions, likely to be asked by beginners. 3.*) Intermediate questions. 4.*) Advanced questions, likely to be asked by people who thought they already knew all of the answers. 5.*) Questions pertaining to the various shells, and the differences. 6.*) An overview of Unix variants. 7.*) An comparison of configuration management systems (RCS, SCCS). This article includes answers to: 7.1) RCS vs SCCS: Introduction 7.2) RCS vs SCCS: How do the interfaces compare? 7.3) RCS vs SCCS: What's in a Revision File? 7.4) RCS vs SCCS: What are the keywords? 7.5) What's an RCS symbolic name? 7.6) RCS vs SCCS: How do they compare for performance? 7.7) RCS vs SCCS: Version Identification. 7.8) RCS vs SCCS: How do they handle with problems? 7.9) RCS vs SCCS: Conversion. 7.10) RCS vs SCCS: Support 7.11) RCS vs SCCS: Command Comparison 7.12) RCS vs SCCS: Acknowledgements 7.13) Can I get more information on configuration management systems? If you're looking for the answer to, say, question 7.5, and want to skip everything else, you can search ahead for the regular expression "^7.5)". While these are all legitimate questions, they seem to crop up in comp.unix.questions or comp.unix.shell on an annual basis, usually followed by plenty of replies (only some of which are correct) and then a period of griping about how the same questions keep coming up. You may also like to read the monthly article "Answers to Frequently Asked Questions" in the newsgroup "news.announce.newusers", which will tell you what "UNIX" stands for. With the variety of Unix systems in the world, it's hard to guarantee that these answers will work everywhere. Read your local manual pages before trying anything suggested here. If you have suggestions or corrections for any of these answers, please send them to to tmatimar@empress.com. 7.1) RCS vs SCCS: Introduction Date: Sat, 10 Oct 92 19:34:39 +0200 From: Bill Wohler The majority of the replies (in a recent poll) were in favor of RCS, a few for SCCS, and a few suggested alternatives such as CVS. Functionally RCS and SCCS are practically equal, with RCS having a bit more features since it continues to be updated. Note that RCS learned from the mistakes of SCCS... 7.2) RCS vs SCCS: How do the interfaces compare? Date: Sat, 10 Oct 92 19:34:39 +0200 From: Bill Wohler RCS has an easier interface for first time users. There are less commands, it is more intuitive and consistent, and it provides more useful arguments. Branches have to be specifically created in SCCS. In RCS, they are checked in as any other version. 7.3) RCS vs SCCS: What's in a Revision File? Date: Sat, 10 Oct 92 19:34:39 +0200 From: Bill Wohler RCS keeps history in files with a ",v" suffix. SCCS keeps history in files with a "s." prefix. RCS looks for RCS files automatically in the current directory or in a RCS subdirectory, or you can specify an alternate RCS file. The sccs front end to SCCS always uses the SCCS directory. If you don't use the sccs front end, you must specify the full SCCS filename. RCS stores its revisions by holding a copy of the latest version and storing backward deltas. SCCS uses a "merged delta" concept. All RCS activity takes place within a single RCS file. SCCS maintains several files. This can be messy and confusing. Editing either RCS or SCCS files is a bad idea because mistakes are so easy to make and so fatal to the history of the file. Revision information is easy to edit in both types, whereas one would not want to edit the actual text of a version in RCS. If you edit an SCCS file, you will have to recalculate the checksum using the admin program. 7.4) RCS vs SCCS: What are the keywords? Date: Sat, 10 Oct 92 19:34:39 +0200 From: Bill Wohler RCS and SCCS use different keywords that are expanded in the text. For SCCS the keyword "%I%" is replaced with the revision number if the file is checked out for reading. The RCS keywords are easier to remember, but keyword expansion is more easily customized in SCCS. In SCCS, keywords are expanded on a read-only get. If a version with expanded keywords is copied into a file that will be deltaed, the keywords will be lost and the version information in the file will not be updated. On the other hand, RCS retains the keywords when they are expanded so this is avoided. 7.5) What's an RCS symbolic name? Date: Sat, 10 Oct 92 19:34:39 +0200 From: Bill Wohler RCS allows you treat a set of files as a family of files while SCCS is meant primarily for keeping the revision history of files. RCS accomplishes that with symbolic names: you can mark all the source files associated with an application version with `rcs -n', and then easily retrieve them later as a cohesive unit. In SCCS you would have to do this by writing a script to write or read all file names and versions to or from a file. 7.6) RCS vs SCCS: How do they compare for performance? Date: Sat, 10 Oct 92 19:34:39 +0200 From: Bill Wohler Since RCS stores the latest version in full, it is much faster in retrieving the latest version. After RCS version 5.6, it is also faster than SCCS in retrieving older versions. 7.7) RCS vs SCCS: Version Identification. Date: Sat, 10 Oct 92 19:34:39 +0200 From: Bill Wohler SCCS is able to determine when a specific line of code was added to a system. 7.8) RCS vs SCCS: How do they handle with problems? Date: Sat, 10 Oct 92 19:34:39 +0200 From: Bill Wohler If you are missing the sccs or rcs tools, or the RCS or SCCS file is corrupt and the tools don't work on it, you can still retrieve the latest version in RCS. Not true with SCCS. 7.9) RCS vs SCCS: Conversion. Date: Sat, 10 Oct 92 19:34:39 +0200 From: Bill Wohler RCS provides a program to convert from SCCS to RCS. One would have to write his own program to convert from RCS to SCCS. 7.10) RCS vs SCCS: Support Date: Sat, 10 Oct 92 19:34:39 +0200 From: Bill Wohler SCCS is supported by AT&T. RCS is supported by the Free Software Foundation. Therefore RCS runs on many more platforms, including PCs. Most make programs recognize SCCS's "s." prefix while GNU make is one of the few that handles RCS's ",v" suffix. Some tar programs have a -F option that ignores either RCS directories, or SCCS directories or both. 7.11) RCS vs SCCS: Command Comparison Date: Sat, 10 Oct 92 19:34:39 +0200 From: Bill Wohler SCCS RCS Explanation ==== === =========== sccs admin -i -nfile file ci file Checks in the file for the first time, creating the revision history file. sccs get file co file Check out a file for reading. sccs edit file co -l file Check out a file for modification. sccs delta file ci file Check in a file previously locked. what file ident file Print keyword information. sccs prs file rlog file Print a history of the file. sccs sccsdiff -rx -ry file rcsdiff -rx -ry file Compare two revisions. sccs diffs file rcsdiff file Compare current with last revision. sccs edit -ix-y file rcsmerge -rx-y file Merge changes between two versions into file. ??? rcs -l file Lock the latest revision. ??? rcs -u file Unlock the latest revision. Possible to break another's lock, but mail is sent to the other user explaining why. 7.12) RCS vs SCCS: Acknowledgements Date: Sat, 10 Oct 92 19:34:39 +0200 From: Bill Wohler I would like to thank the following persons for contributing to these articles. I'd like to add your name to the list--please send comments or more references to Bill Wohler . Karl Vogel Mark Runyan Paul Eggert Greg Henderson Dave Goldberg Rob Kurver Raymond Chen Dwight 7.13) Can I get more information on configuration management systems? Date: Thu Oct 15 10:27:47 EDT 1992 From: Ted Timar Bill Wohler, who compiled all of the information in this part of the FAQ, has compiled much more information. This information is available for ftp from ftp.wg.omron.co.jp (133.210.4.4) under "pub/unix-faq/docs/rev-ctl-sys".