GNU RCS

The Revision Control System (RCS) manages multiple revisions of files. RCS automates the storing, retrieval, logging, identification, and merging of revisions. RCS is useful for text that is revised frequently, including source code, programs, documentation, graphics, papers, and form letters.

RCS was first developed by Walter F. Tichy at Purdue University in the early 1980s -- paper: RCS: A System for Version Control (1991) (troff, PostScript, PDF). See also the Purdue RCS Homepage.

RCS design is an improvement from its predecessor Source Code Control System (SCCS) (see GNU CSSC). The improvements include an easier user interface and improved storage of versions for faster retrieval. RCS improves performance by storing an entire copy of the most recent version and then stores reverse differences (called "deltas"). RCS uses GNU Diffutils to find the differences between versions.

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(FTP mirrors)

Latest release: 5.10.0 (2020-10-20)

• bug fixes

  • RCS file search skipped RCS/FILENAME by default

    The default set of candidate filenames for the RCS file is:

     RCS/FILENAME,v
     RCS/FILENAME
     FILENAME,v

    RCS 5.8 (released 2011-08-30) introduced a bug which caused the default RCS file search to skip RCS/FILENAME. Regression fixed.

  • ‘rlog -w’ behaved like ‘rlog’ (sans ‘-w’)

    RCS 5.8 (released 2011-08-30) introduced a bug which caused ‘rlog -w’ (without any logins specified) to fail to default to the user login. Instead it behaved as if option ‘-w’ were omitted entirely.

    The cases where logins are specified (e.g., ‘rlog -wjrhacker’) were not affected.

  • missing string in comma-v detected, diagnosed

    Previously, if foo,v contained fragment:

     1.1
     log
     text
     @@

    i.e., there was no string value following the ‘log’ keyword, then rlog (et al) would interpret that as an "empty log message" instead of as a violation of the RCS file format grammar, which stipulates that a string value must follow the keywords ‘desc’, ‘log’ and ‘text’ -- (info "(rcs) comma-v grammar").

    Now, such a situation causes rlog (et al) to abort w/ message "missing string after KEYWORD" (KEYWORD ∈ {desc, log, text}).

  • subsecond resolution maintained for ‘-d’, ‘-T’

    An RCS ‘delta’ includes a ‘date’ component w/ second (whole number) resolution. Previously, on filesystems that support subsecond (fractional) resolution for the file modification time (aka "mtime"), RCS commands given the ‘-d’ and/or ‘-T’ options would disregard, on read, and specify 0 (zero), on write, the fractional mtime.

    Now, RCS preserves subsecond mtime in those cases. More details in new manual section -- (info "(rcs) Stamp resolution").

• portability fixes

  • now buildable under ‘gcc -std=c11’ (default for GCC 5)

    RCS previously failed to build under ‘-std=c11’, which happens to be the default mode of GCC 5. In particular, ‘-std=c11’ is more strict about function attributes syntax than ‘-std=c99’.

    Now, the offending code has been rectified. (Specifically, attribute ‘_Noreturn’ now is at the start of a func decl.)

  • threads support

    RCS itself is clueless about threads, but it uses gnulib, which may or may not require threads support. This manifests as the configure script options ‘--enable-threads=MODEL’ as well as ‘--disable-threads’.

    Previously, "make" would ignore MODEL (even implicitly), acting as if ‘--disable-threads’ were specified. Now, it takes into account MODEL by propagating makefile var ‘LIBTHREAD’.

  • consult ‘USER’ first if ‘LOGNAME’ read-only

    To determine the user (login) name in the absence of a specific command-line option, RCS normally checks first the env var ‘LOGNAME’ and second, ‘USER’. Alas, this is unworkable under AIX, where ‘LOGNAME’ is read-only. So now, if the configure script finds ‘LOGNAME’ to be read-only, it arranges to build RCS to check ‘USER’ first and then ‘LOGNAME’. See README.

  • configure script avoids ‘date -r’

    Unfortunately ‘date -r’ is not POSIX. This made AIX unhappy.

  • other AIX accomodation

    The AIX compiler complains about the implicit casting that occurs when returning a pointer from a function whose return type is ‘bool’. So, we are now explicit.

• documentation improvements

  • docfix: add "Log message option" to Detailed Node Listing

    Probably Emacs by now has some automagic way to sync the ‘@detailmenu’ section w/ the text body... hmmm.

  • style change due to ‘-zZONE’ option

    Specifying option ‘-zZONE’ to ‘rcs log’ changes the date output style to use hyphens (ISO) instead of slashes (YYYY/MM/DD).

  • rlog, use with CVS

    Since RCS 5.8 (released 2011-08-30), there have been sporadic reports of rlog (aka "rcs log") failing with CVS files. The manual now addresses this -- (info "(rcs) comma-v particulars").

  • delim-separated list

    GNU RCS has always supported comma to separate items in a list (e.g., ‘rcs frob -o1.1,2.2’ to remove (or "outdate") revisions 1.1 and 2.2). But did you know that most places a comma is welcome and you can use other delimiter characters as well? Read all about it -- (info "(rcs) Delim-separated list").

  • (style) pargraphs no longer indented

    This looks nicer (IMHO) for Info and Text output formats.

• testing improvements

  Many new tests and test cases for existing tests were added, to catch regressions and exercise infrequent code paths. For "make check" (locally), function coverage is 97.3% (considered "high") and line coverage is 84.9% (considered "medium"), per lcov.

• bootstrap/maintenance tools

  upgraded:

   GNU gnulib 2020-10-19 23:37:09
   GNU texinfo 6.7
   GNU Automake 1.16.2
   GNU Autoconf 2.69c

  as before:

   (none)

(unadorned)

Documentation

Documentation for RCS is available online, as is documentation for most GNU software.  You may also find more information about RCS by running info rcs or by looking at /usr/share/doc/rcs/, /usr/local/doc/rcs/, or similar directories on your system. 

Mailing Lists

RCS has the following mailing lists:

• bug-rcs is for reporting bugs.
• help-rcs is for feature requests and user support.

Announcements about RCS and most other GNU software are made on info-gnu (archive). 

Security reports that should not be made immediately public can be sent directly to the maintainer.  If there is no response to an urgent issue, you can escalate to the general security mailing list for advice. 

Getting involved

Development of RCS, and GNU in general, is a volunteer effort, and you can contribute.  For information, please read How to help GNU.  If you'd like to get involved, it's a good idea to join the discussion mailing list (see above). 

Development

For development sources, issue trackers, and other information, please see the RCS project page at savannah.gnu.org. 

Maintainer

RCS is currently being maintained by Thien-Thi Nguyen (tip jar).  Please use the mailing lists for contact. 

Licensing

RCS is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.