Unix - Frequently Asked Questions (7/7)
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 problems?
- 7.9) RCS vs SCCS: How do they interact with make(1)?
- 7.10) RCS vs SCCS: Conversion
- 7.11) RCS vs SCCS: Support
- 7.12) RCS vs SCCS: Command Comparison
- 7.13) RCS vs SCCS: Acknowledgements
- 7.14) 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@isgtec.com.
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Subject: RCS vs SCCS: Introduction
Date: Sat, 10 Oct 92 19:34:39 +0200
>From: Bill Wohler
7.1) RCS vs SCCS: Introduction
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...
------------------------------
Subject: RCS vs SCCS: How do the interfaces compare?
Date: Sat, 10 Oct 92 19:34:39 +0200
>From: Bill Wohler
7.2) RCS vs SCCS: How do the interfaces compare?
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.
------------------------------
Subject: RCS vs SCCS: What's in a Revision File?
Date: Sat, 10 Oct 92 19:34:39 +0200
>From: Bill Wohler
7.3) RCS vs SCCS: What's in a Revision File?
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.
------------------------------
Subject: RCS vs SCCS: What are the keywords?
Date: Sat, 10 Oct 92 19:34:39 +0200
>From: Bill Wohler
7.4) RCS vs SCCS: What are the keywords?
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.
------------------------------
Subject: What's an RCS symbolic name?
Date: Sat, 10 Oct 92 19:34:39 +0200
>From: Bill Wohler
7.5) What's an RCS symbolic name?
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.
------------------------------
Subject: RCS vs SCCS: How do they compare for performance?
Date: Sat, 10 Oct 92 19:34:39 +0200
>From: Bill Wohler
7.6) RCS vs SCCS: How do they compare for performance?
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.
------------------------------
Subject: RCS vs SCCS: Version Identification.
Date: Sat, 10 Oct 92 19:34:39 +0200
>From: Bill Wohler
7.7) RCS vs SCCS: Version Identification.
SCCS is able to determine when a specific line of code was added
to a system.
------------------------------
Subject: RCS vs SCCS: How do they handle problems?
Date: Sat, 10 Oct 92 19:34:39 +0200
>From: Bill Wohler
7.8) RCS vs SCCS: How do they handle problems?
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.
------------------------------
Subject: RCS vs SCCS: How do they interact with make(1)?
Date: Wed, 30 Dec 1992 10:41:51 -0700
>From: Blair P. Houghton
7.9) RCS vs SCCS: How do they interact with make(1)?
The fact that SCCS uses prefixes (s.file.c) means that make(1)
can't treat them in an ordinary manner, and special rules
(involving '~' characters) must be used in order for make(1) to
work with SCCS; even so, make(1) on some UNIX platforms will not
apply default rules to files that are being managed with SCCS.
The suffix notation (file.c,v) for RCS means that ordinary
suffix-rules can be used in all implementations of make(1), even
if the implementation isn't designed to handle RCS files
specially.
------------------------------
Subject: RCS vs SCCS: Conversion.
Date: Tue, 10 Jan 1995 21:01:41 -0500
>From: Ed Ravin
7.10) RCS vs SCCS: Conversion.
An unsupported C-Shell script is available to convert from SCCS
to RCS. You can find it in
ftp://ftp.std.com/src/gnu/cvs-1.3/contrib/sccs2rcs
One would have to write their own script or program to convert
from RCS to SCCS.
------------------------------
Subject: RCS vs SCCS: Support
Date: Sat, 10 Oct 92 19:34:39 +0200
>From: Bill Wohler
7.11) RCS vs SCCS: Support
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.
------------------------------
Subject: RCS vs SCCS: Command Comparison
Date: Sat, 10 Oct 92 19:34:39 +0200
>From: Bill Wohler
7.12) RCS vs SCCS: Command Comparison
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.
------------------------------
Subject: RCS vs SCCS: Acknowledgements
Date: Sat, 10 Oct 92 19:34:39 +0200
>From: Bill Wohler
7.13) RCS vs SCCS: Acknowledgements
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
------------------------------
Subject: Can I get more information on configuration management systems?
Date: Thu Oct 15 10:27:47 EDT 1992
>From: Ted Timar
7.14) Can I get more information on configuration management systems?
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".
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